The Black Book of Psychotropic Dosing and Monitoring.

Introduction Since the last edition of the Black Book, several innovative agents have been approved or are poised to be approved in the coming year. These include novel antidepressants, the first muscarine agonist for the treatment of schizophrenia, the first psychedelic which may be approved for the treatment of PTSD (Post Traumatic Stress Disorder), and the first disease modifying drug for the treatment of Alzheimer's disease. Three new antidepressants have come to the market in the past 18 months. The first of those, Auvelity, the combination of bupropion and dextromethorphan, takes advantage of a pharmacokinetic and pharmacodynamic synergism between the two drugs.85 Dextromethorphan has several pharmacodynamic properties including actions on the NMDA receptor and the Sigma 1 receptor, adding to the indirect norepinephrine agonist properties of bupropion. How Dextromethorphan is rapidly metabolized via the CYP2D6 isoenzyme to dextrophan that may have mu opioid agonist properties. The combination with bupropion, a CYP2D6 inhibitor, inhibits the metabolism of dextromethorphan allowing for more consistent therapeutic levels. The combination of dextromethorphan 45 mg twice per day and bupropion SR 105 mg twice daily appears to be more effective than an equivalent dose of bupropion alone both in speeding up antidepressant response and achieving remission. However, it's not clear at this time how the combination would compare with a more typical dose of bupropion of 300-450 milligrams a day range. The phase III program for Auvelity, showed that the drug was well tolerated with the most common side effects being dizziness, headache, and dry mouth.86 Another novel antidepressant agent approved in 2023 is zuranolone (Zurzuvae). Zuranolone is an oral analog of IV brexanalone, and like brexanolone, was approved for the treatment of post-partum depression.83 The advantages of zuranolone over brexanalone are many. While brexanolone is a 60-hour intravenous infusion that must be administered in a health care facility, zuranolone is a once/day oral medication that is usually taken at home. Like brexanolone, and unlike most antidepressants, zuranolone has a short course of treatment, lasting just 14 days. Zuranolone's, as does brexanolone, is thought to act primarily as allosteric modulator of the GABA-a receptors. Despite only 14 days of treatment, zuranolone produced in depression in post-partum patients a clinically and significantly meaningful improvement at day 15 and continued to day 45 or 1 month past the end of treatment. Zuranolone is a schedule IV drug. The most common side effect in clinical trials was somnolence with 36% of participants reporting this side effect vs only 6% of those on placebo.84 Other common side effects included dizziness, diarrhea and fatigue. While the FDA declined to approve zuranolone as monotherapy or as an adjunctive treatment to standard antidepressants in major depression itself, there are positive studies in non-post-partum major depression albeit with smaller effect sizes and less consistent duration of activity. It is likely that zuranolone will continue to be studied in other depressive syndromes such as depression with anxious distress. The third "new" antidepressant approved late 2023 was gepirone (Exxua). Gepirone is not exactly a new or novel antidepressant and originally sought approval in the US about 20 years ago.88 There had been two positive studies of gepirone during the original NDA application but also a number of failed, negative, or non-informative studies as well. Thus, the FDA declined to originally approve the drug. However, failed and negative trials are common with antidepressants and after much internal debate, the FDA ultimately agreed to approve the drug based on the positive trials and a relatively favorable side effect profile. Gepirone, like buspirone, is a partial agonist of the 5HT1a receptor and a 5HT2 antagonist. As such, gepirone does not tend to be associated with sexual side effects, weight gain, or sedation. The most common side effects are dizziness, nausea, and insomnia which tend to improve in many patients over time. Second generation antipsychotics (SGAs) continue to be the only class of agents [other than esketamine (Spravato)] approved in adjunctive treatment of resistant major depression. In addition to olanzapine (combined with fluoxetine; Symbyax), aripiprazole (Abilify), quetiapine (Seroquel), brexpiprazole (Rexulti), cariprazine (Vraylar) became the latest SGA to be approved in 2022.90 Adjunctive cariprazine at 1.5 mg daily was significantly more effective than adjunctive placebo in patients with MDD who had failed to achieve an adequate response with an antidepressant alone after 6 weeks of treatment. Interestingly, a 3 mg dose of cariprazine was less consistently effective.91 The major advantage of cariprazine over some of the other approved adjunctive SGA's is easy dosing, with the starting 1.5 mg dose being the optimal therapeutic dose for most people, and a lower metabolic side effect burden with most subjects having limited or no weight gain in short term trials. The most common side effect were akathisia/restlessness, fatigue, and nausea. Lumateperone (Caplyta) is also has positive phase III data in the adjunctive treatment of major depression and is expective file for approval in late 2024. Another recent major development in psychopharmacology is the reemergence of psychedelics in the treatment of psychiatric disorders. The first of these is MDMA (phenethylamine 3,4-methylenedioxymethamphetamine) assisted psychotherapy for the treatment of PTSD. A New Drug Application (NDA) was accepted by the FDA for MDMA in the treatment of PTSD in late 2023.87 Because the drug is being fast tracked as a "breakthrough" treatment by the FDA, it was expected to see approval in the summer of 2024. The phase II and III data for MDMA assisted psychotherapy in the treatment of PTSD have been quite consistent and impressive. However, independent reviews have pointed to significant deficiencies in these studies including the bias introduced because of functional unblinding; virtually all patients in psychedelic studies can guess whether they got the active drug or placebo. The functional unblinding, the lack of standardization of adjunctive psychotherapy as well as the abuse potential of MDMA, may delay an FDA approval. The typical regimen in these trials included 3 preparatory psychotherapy sessions followed by once/month dosing sessions (lasting about 8 hours) and using doses of 120-160 mg in a split dose. There were typically 3 monthly dosing sessions, each followed by 3 integrative psychotherapy sessions to help subjects process and understand their experiences during the dosing sessions. In the most recent phase 3 trials, over 70% of subjects no longer met criteria for PTDS compared to 46% of those treated with psychotherapy and placebo alone.89 The only approved medications for treating PTSD are two SSRIs, paroxetine and sertraline. These drugs effect only some dimensions of PTSD with only 20-30% achieving a remission level response with these drugs. Thus, MDMA assisted psychotherapy appears to achieve much higher levels of remission and response than has been true for the SSRIs. Since MDMA is not taken continuously, side effects from MDMA tend to be short lived. Side effects have included muscle tightness, nausea, diminished appetite, excessive sweating, feeling cold and dizziness among others. Since MDMA is currently a schedule I drug, it is likely that a rigorous Risk Evaluation Mitigation (REMs) program will be put in place and a limited number of centers and clinicians will be designated to perform MDMA assisted psychotherapy for PTSD. In addition to MDMA, psilocybin-assisted psychotherapy is in phase 3 trials for treating resistant depression but unlikely to be available before late 2025 at the earliest. An argument can be made that there has not been a truly novel antipsychotic since the introduction of clozapine in the US in 1990. All first-generation antipsychotics have been dopamine 2 antagonists and second-generation drugs have involved some ratio of 5HT2 antagonism to D2 blockade. In 2023, the FDA accepted the application of xenomaline/tropsium (KarXT) which may become the first muscarinic M1M4 agonist approved for the treatment of schizophrenia.82,83 Tropsium is added as a muscarine antagonist to block the peripheral cholinergic effects of a muscarine agonist. Xenomaline/tropsium appears to be effective in treating both positive and negative symptoms of schizophrenia. In a phase 3 study of 407 patients with schizophrenia, xenomaline/tropsium at doses of xenomaline/50 mg/tropsium 20 mg twice daily up to 125 mg/30 mg twice daily was significantly more effective than placebo in treating both and negative symptoms over 5 weeks of treatment. As would be expected, the side effect profile of xenomaline/tropsium is very different that all currently available antipsychotics. There is no risk of EPS as it is not a dopamine antagonist, and xenomaline/tropsium is not associated with significant metabolic effects. The side effects are cholinergic in nature and include constipation, dry mouth, and nausea. A decision is expected in September of 2024. The year 2023 also saw the approval of the first disease modifying drug in the treatment of Alzheimer's disease, lecanemab (Lequembi). While acetylcholinesterase inhibitors and memantine have been available for decades, these drugs modestly improve cognition in Alzheimer's disease patients and do not alter the progressive course of the illness. Lecanemab is an IV monoclonal antibody that targets the removal of beta-amyloid in the brain as well proto-fibrils that are also known to be toxic to neuronal tissue. When given early in the course of the illness, patients treated with Lecanemab showed 27% less decline on some measures of cognition and function thandid patients treated with a placebo over 18 months (about 1 and a half years). It is not known whether treatment for longer than 18 months would show lesser or greater decline over time. However, there are simulation studies that suggest that Lecanemab may modestly reduce the number of patients who progress to severe Alzheimer's disease and require institutional care. The standard dose is 10 mg/kg given via IV over one hour every 2 weeks for 18 months. Lecanemab is typically administered in an infusion center so that side effects can be monitored. The most serious side effects of Lecanemab are amyloid related imaging abnormalities (ARIA) that are associated with brain edema and microhemorrhages. ARIA can occur in up to 15% of patients. More common side effects are headache and nausea. While it remains to be seen how useful these new agents will be in clinical practice, they do represent an approach to treating neuropsychiatric disorders that are a notable departure from the pharmacotherapy of the past half century. It seems likely that some patients who have not been able to respond to or tolerate traditional pharmacotherapy will find hope in these new medications.

Impact of Viloxazine Extended-Release Capsules (Qelbree®) on Select Cytochrome P450 Enzyme Activity and Evaluation of CYP2D6 Genetic Polymorphisms on Viloxazine Pharmacokinetics.

BACKGROUND AND OBJECTIVE: Viloxazine extended-release (ER) [Qelbree®] is a nonstimulant attention-deficit/hyperactivity disorder (ADHD) treatment. In vitro studies suggested potential for viloxazine to inhibit cytochrome 450 (CYP) enzymes 1A2, 2B6, 2D6 and 3A4. This clinical study therefore evaluated viloxazine ER effects on index substrates for CYP1A2, 2D6, and 3A4, and secondarily evaluated the impact of CYP2D6 polymorphisms on viloxazine pharmacokinetics. METHODS: Thirty-seven healthy subjects received a modified Cooperstown cocktail (MCC; caffeine 200 mg, dextromethorphan 30 mg, midazolam 0.025 mg/kg) on Day 1, viloxazine ER 900 mg/day on Days 3-5, and a combination of viloxazine ER 900 mg and MCC on Day 6. Viloxazine ER effects on MCC substrates were evaluated using analysis of variance. The impact of CYP2D6 genetic polymorphisms on steady-state viloxazine plasma concentrations was evaluated using Student's t test assessing pharmacokinetic parameter differences between poor versus extensive metabolizers. RESULTS: The least squares geometric mean ratio [GMR%] (90% CI) of MCC substrate + viloxazine ER/MCC substrate alone for caffeine maximum concentration (Cmax), area under the plasma concentration-time curve from time 0 to the last quantifiable concentration (AUCt), and area under the plasma concentration-time curve from time 0 extrapolated to infinity (AUC∞) was 99.11 (95.84-102.49), 436.15 (398.87-476.92), and 583.35 (262.41-1296.80), respectively; 150.76 (126.03-180.35), 185.76 (155.01-222.61), and 189.71 (160.37-224.42) for dextromethorphan Cmax, AUCt, and AUC∞, respectively; and 112.81 (104.71-121.54), 167.56 (153.05-183.45), and 168.91 (154.38-184.80) for midazolam Cmax, AUCt, and AUC∞, respectively. At steady state, viloxazine least squares GMR (90% CI) for poor/extensive CYP2D6 metabolizers were Cmax 120.70 (102.33-142.37) and area under the plasme concentration-time curve from time 0 to 24 hours (AUC0-24 125.66 (105.36-149.87)). CONCLUSION: Viloxazine ER is a strong CYP1A2 inhibitor and a weak CYP2D6 and CYP3A4 inhibitor. CYP2D6 polymorphisms did not meaningfully alter the viloxazine ER pharmacokinetic profile.

Effect of one-year dextromethorphan/quinidine treatment on management of respiratory impairment in amyotrophic lateral sclerosis.

Treatment with Dextromethorphan/Quinidine (DM/Q) has demonstrated benefit on pseudobulbar affect and bulbar function in amyotrophic lateral sclerosis (ALS). The aim of this study was to assess whether DM/Q could provide long-term improvement in bulbar function and thereby prolong noninvasive respiratory management in ALS. MATERIALS AND METHODS: This prospective, case-cohort study, recruited ALS patients with bulbar dysfunction. Subjects included were compared with cross-matched historical controls. Cases received DM/Q (20/10 mg twice daily) during one-year follow-up; bulbar dysfunction was evaluated with the Norris scale bulbar subscore (NBS) and bulbar subscale of AlSFRS-R (ALSFRSb). RESULTS: In total, 21 cases and 20 controls were enrolled, of whom noninvasive respiratory muscle assistance failed in 6 (28.5%) patients in the DM/Q group, compared with 4 patients (20.0%) in the control group (p = 0.645). Time from study onset to failure of respiratory muscle aids was 5.50 + 1.31 months in the DM/Q group and 5.20 + 1.15 months in the control group (p = 0.663). The adjusted OR for the effect of treatment on failure of noninvasive respiratory muscle aids was 2.12 (95%CI 0.23-33.79, p = 0.592). In the DM/Q group an impairment in scores was found in NBS (F = 19.26, p = 0.000) and ALSFRS-Rb (F = 12.71, p = 0.001) across different months of the study. CONCLUSION: Treatment with DM/Q in ALS is unable to prolong noninvasive respiratory management, and moreover, has no effect on long-term deterioration of bulbar function. Notwithstanding the results on bulbar function, DM/Q was found to improve pseudobulbar affect during one-year follow-up.

Napabucasin Drug-Drug Interaction Potential, Safety, Tolerability, and Pharmacokinetics Following Oral Dosing in Healthy Adult Volunteers.

Napabucasin is an orally administered reactive oxygen species generator that is bioactivated by the intracellular antioxidant nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1. Napabucasin induces cell death in cancer cells, including cancer stem cells. This phase 1 study (NCT03411122) evaluated napabucasin drug-drug interaction potential for 7 cytochrome P450 (CYP) enzymes and the breast cancer resistance protein transporter/organic anion transporter 3. Healthy volunteers who tolerated napabucasin during period 1 received probe drugs during period 2, and in period 3 received napabucasin (240 mg twice daily; days 1-11) plus a phenotyping cocktail containing omeprazole (CYP2C19), caffeine (CYP1A2), flurbiprofen (CYP2C9), bupropion (CYP2B6), dextromethorphan (CYP2D6), midazolam (CYP3A) (all oral; day 6), intravenous midazolam (day 7), repaglinide (CYP2C8; day 8), and rosuvastatin (breast cancer resistance protein/organic anion transporter 3; day 9). Drug-drug interaction potential was evaluated in 17 of 30 enrolled volunteers. Napabucasin coadministration increased the area under the plasma concentration-time curve from time 0 extrapolated to infinity (geometric mean ratio [90% confidence interval]) of caffeine (124% [109.0%-141.4%]), intravenous midazolam (118% [94.4%-147.3%]), repaglinide (127% [104.7%-153.3%]), and rosuvastatin (213% [42.5%-1068.3%]) and decreased the area under the plasma concentration-time curve from time 0 extrapolated to infinity of dextromethorphan (71% [47.1%-108.3%]), bupropion (79% [64.6%-97.0%]), and hydroxybupropion (45% [15.7%-129.6%]). No serious adverse events/deaths were reported. Generally, napabucasin is not expected to induce/inhibit drug clearance to a clinically meaningful degree.

TMS-EEG signatures of glutamatergic neurotransmission in human cortex.

Neuronal activity in the brain reflects an excitation-inhibition balance that is regulated predominantly by glutamatergic and GABAergic neurotransmission, and often disturbed in neuropsychiatric disorders. Here, we tested the effects of a single oral dose of two anti-glutamatergic drugs (dextromethorphan, an NMDA receptor antagonist; perampanel, an AMPA receptor antagonist) and an L-type voltage-gated calcium channel blocker (nimodipine) on transcranial magnetic stimulation (TMS)-evoked electroencephalographic (EEG) potentials (TEPs) and TMS-induced oscillations (TIOs) in 16 healthy adults in a pseudorandomized, double-blinded, placebo-controlled crossover design. Single-pulse TMS was delivered to the hand area of left primary motor cortex. Dextromethorphan increased the amplitude of the N45 TEP, while it had no effect on TIOs. Perampanel reduced the amplitude of the P60 TEP in the non-stimulated hemisphere, and increased TIOs in the beta-frequency band in the stimulated sensorimotor cortex, and in the alpha-frequency band in midline parietal channels. Nimodipine and placebo had no effect on TEPs and TIOs. The TEP results extend previous pharmaco-TMS-EEG studies by demonstrating that the N45 is regulated by a balance of GABAAergic inhibition and NMDA receptor-mediated glutamatergic excitation. In contrast, AMPA receptor-mediated glutamatergic neurotransmission contributes to propagated activity reflected in the P60 potential and midline parietal induced oscillations. This pharmacological characterization of TMS-EEG responses will be informative for interpreting TMS-EEG abnormalities in neuropsychiatric disorders with pathological excitation-inhibition balance.

Efficacy of dextromethorphan for the treatment of depression: a systematic review of preclinical and clinical trials.

INTRODUCTION: The large percentage of adults with major depressive disorder (MDD) insufficiently responding and/or tolerating conventional monoamine-based antidepressants invites the need for mechanistically novel treatments. Convergent evidence implicates glutamatergic signaling as a potential therapeutic target in MDD. AREAS COVERED: The synthesis herein of preclinical and clinical studies indicates that dextromethorphan (DXM) is well tolerated and exhibits clinically significant antidepressant effects; DXM combined with bupropion has demonstrated replicated and relatively rapid onset efficacy in adults with MDD. DXM efficacy has been preliminarily reported in adults with bipolar depression. The combination of DXM and bupropion represents a pharmacokinetic and pharmacodynamic synergy which may account for the rapidity of action in MDD. EXPERT OPINION: The combination of DXM and bupropion is a safe, well tolerated and efficacious treatment option in adults with MDD. Priority questions are whether DXM/bupropion is uniquely effective across discrete domains of psychopathology (e.g. anhedonia, reward processing, general cognitive systems) and/or whether it is able to significantly improve patient-reported outcomes (e.g. quality of life, psychosocial functioning). The availability of ketamine/esketamine and DXM/bupropion instantiates the relevance of glutamate as a treatment target in MDD. Studies in bipolar depression with DXM/bupropion are warranted as well as in MDD with suicidality.

N-Substituted-3-alkoxy-derivatives of dextromethorphan are functional NMDA receptor antagonists in vivo: Evidence from an NMDA-induced seizure model in rats.

Interest in developing NMDA receptor antagonists with reduced side-effects for neurological and psychiatric disorders has been re-energized by the recent introduction of esketamine into clinical practice for treatment-resistant depression. Structural analogs of dextromethorphan bind with low affinity to the NMDA receptor ion channel, have functional effects in vivo, and generally display a lower propensity for side-effects than that of ketamine and other higher affinity antagonists. As such, the aim of the present study was to determine whether a series of N-substituted-3-alkoxy-substituted dextromethorphan analogs produce their anticonvulsant effects through NMDA receptor blockade. Compounds were studied against NMDA-induced seizures in rats. Compounds were administered intracerebroventricularly in order to mitigate confounds of drug metabolism that arise from systemic administration. Comparison of the anticonvulsant potencies to their affinities for NMDA, σ1, and σ2 binding sites were made in order to evaluate the contribution of these receptors to anticonvulsant efficacy. The potencies to block convulsions were positively associated with their affinities to bind to the NMDA receptor ion channel ([3H]-TCP binding) (r = 0.71, p < 0.05) but not to σ1 receptors ([3H]-SKF 10047 binding) (r = -0.31, p = 0.46) or to σ2 receptors ([3H]-DTG binding) (p = -0.38, p = 0.36). This is the first report demonstrating that these dextromethorphan analogs are functional NMDA receptor antagonists in vivo. Given their potential therapeutic utility and favorable side-effect profiles, such low affinity NMDA receptor antagonists could be considered for further development in neurological (e.g., anticonvulsant) and psychiatric (e.g., antidepressant) disorders.

Use and abuse of dissociative and psychedelic drugs in adolescence.

Adolescence is a period of profound developmental changes, which run the gamut from behavioral and neural to physiological and hormonal. It is also a time at which there is an increased propensity to engage in risk-taking and impulsive behaviors like drug use. This review examines the human and preclinical literature on adolescent drug use and its consequences, with a focus on dissociatives (PCP, ketamine, DXM), classic psychedelics (LSD, psilocybin), and MDMA. It is the case for all the substances reviewed here that very little is known about their effects in adolescent populations. An emerging aspect of the literature is that dissociatives and MDMA produce mixed reinforcing and aversive effects and that the balance between reinforcement and aversion may differ between adolescents and adults, with consequences for drug use and addiction. However, many studies have failed to directly compare adults and adolescents, which precludes definitive conclusions about these consequences. Other important areas that are largely unexplored are sex differences during adolescence and the long-term consequences of adolescent use of these substances. We provide suggestions for future work to address the gaps we identified in the literature. Given the widespread use of these drugs among adolescent users, and the potential for therapeutic use, this work will be crucial to understanding abuse potential and consequences of use in this developmental stage.

Dextromethorphan Administration on Day 0 and Day 7 for Secondary Prevention of Methotrexate-induced Neurotoxicity in Childhood Acute Lymphoblastic Leukemia: A Retrospective Case Series.

Acute lymphoblastic leukemia is the most common malignancy in children. Long-term survival exceeds 90%; however, therapy-induced toxicity remains a concern. Methotrexate neurotoxicity (MTX-NT) is common, often necessitating alterations in chemotherapy regimens. Dextromethorphan has been used as an abortive and prophylactic treatment for MTX-NT. The authors report a case series of 7 pediatric patients with acute lymphoblastic leukemia with prior episodes of MTX-NT given a single dose of dextromethorphan (1 to 2 mg/kg) on the day of MTX administration and 7 days later. No subsequent episodes of MTX-NT occurred after 40 intravenous and 81 intrathecal administrations. This specific regimen of secondary prophylaxis may prevent MTX-NT.

Possible New Strategies for the Treatment of Congenital Hyperinsulinism.

Objective: Congenital hyperinsulinism (CHI) is a rare disease characterized by persistent hypoglycemia as a result of inappropriate insulin secretion, which can lead to irreversible neurological defects in infants. Poor efficacy and strong adverse effects of the current medications impede successful treatment. The aim of the study was to investigate new approaches to silence ß-cells and thus attenuate insulin secretion. Research Design and Methods: In the scope of our research, we tested substances more selective and more potent than the gold standard diazoxide that also interact with neuroendocrine ATP-sensitive K+ (KATP) channels. Additionally, KATP channel-independent targets as Ca2+-activated K+ channels of intermediate conductance (KCa3.1) and L-type Ca2+ channels were investigated. Experiments were performed using human islet cell clusters isolated from tissue of CHI patients (histologically classified as pathological) and islet cell clusters obtained from C57BL/6N (WT) or SUR1 knockout (SUR1-/-) mice. The cytosolic Ca2+ concentration ([Ca2+]c) was used as a parameter for the pathway regulated by electrical activity and was determined by fura-2 fluorescence. The mitochondrial membrane potential (ΔΨ) was determined by rhodamine 123 fluorescence and single channel currents were measured by the patch-clamp technique. Results: The selective KATP channel opener NN414 (5 µM) diminished [Ca2+]c in isolated human CHI islet cell clusters and WT mouse islet cell clusters stimulated with 10 mM glucose. In islet cell clusters lacking functional KATP channels (SUR1-/-) the drug was without effect. VU0071063 (30 µM), another KATP channel opener considered to be selective, lowered [Ca2+]c in human CHI islet cell clusters. The compound was also effective in islet cell clusters from SUR1-/- mice, showing that [Ca2+]c is influenced by additional effects besides KATP channels. Contrasting to NN414, the drug depolarized ΔΨ in murine islet cell clusters pointing to severe interference with mitochondrial metabolism. An opener of KCa3.1 channels, DCEBIO (100 µM), significantly decreased [Ca2+]c in SUR1-/- and human CHI islet cell clusters. To target L-type Ca2+ channels we tested two already approved drugs, dextromethorphan (DXM) and simvastatin. DXM (100 µM) efficiently diminished [Ca2+]c in stimulated human CHI islet cell clusters as well as in stimulated SUR1-/- islet cell clusters. Similar effects on [Ca2+]c were observed in experiments with simvastatin (7.2 µM). Conclusions: NN414 seems to provide a good alternative to the currently used KATP channel opener diazoxide. Targeting KCa3.1 channels by channel openers or L-type Ca2+ channels by DXM or simvastatin might be valuable approaches for treatment of CHI caused by mutations of KATP channels not sensitive to KATP channel openers.

Predicting steady-state endoxifen plasma concentrations in breast cancer patients by CYP2D6 genotyping or phenotyping. Which approach is more reliable?

In previous studies, steady-state Z-endoxifen plasma concentrations (ENDOss) correlated with relapse-free survival in women on tamoxifen (TAM) treatment for breast cancer. ENDOss also correlated significantly with CYP2D6 genotype (activity score) and CYP2D6 phenotype (dextromethorphan test). Our aim was to ascertain which method for assessing CYP2D6 activity is more reliable in predicting ENDOss. The study concerned 203 Caucasian women on tamoxifen-adjuvant therapy (20 mg q.d.). Before starting treatment, CYP2D6 was genotyped (and activity scores computed), and the urinary log(dextromethorphan/dextrorphan) ratio [log(DM/DX)] was calculated after 15 mg of oral dextromethorphan. Plasma concentrations of TAM, N-desmethyl-tamoxifen (ND-TAM), Z-4OH-tamoxifen (4OH-TAM) and ENDO were assayed 1, 4, and 8 months after first administering TAM. Multivariable regression analysis was used to identify the clinical and laboratory variables predicting log-transformed ENDOss (log-ENDOss). Genotype-derived CYP2D6 phenotypes (PM, IM, NM, EM) and log(DM/DX) correlated independently with log-ENDOss. Genotype-phenotype concordance was almost complete only for poor metabolizers, whereas it emerged that 34% of intermediate, normal, and ultrarapid metabolizers were classified differently based on log(DM/DX). Multivariable regression analysis selected log(DM/DX) as the best predictor, with patients' age, weak inhibitor use, and CYP2D6 phenotype decreasingly important: log-ENDOss = 0.162 - log(DM/DX) × 0.170 + age × 0.0063 - weak inhibitor use × 0.250 + IM × 0.105 + (NM + UM) × 0.210; (R2  = 0.51). In conclusion, log(DM/DX) seems superior to genotype-derived CYP2D6 phenotype in predicting ENDOss.

Assessment of the rapid and sustained antidepressant-like effects of dextromethorphan in mice.

The glutamatergic system has emerged as a novel pathway for treating major depressive disorder (MDD) with the focus on producing both rapid and sustained antidepressant effects. Dextromethorphan is a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist that has produced antidepressant-like effects in forced swim and tail suspension tests (TST); however, the rapid and sustained antidepressant-like effects of dextromethorphan have not been evaluated. This study evaluated the rapid and sustained (24 h) antidepressant-like effects of dextromethorphan (0-32 mg/kg) in C56BL/6 mice using the novelty-induced hypophagia (NIH) test and TST, respectively. Additionally, we evaluated anxiety-related behavior and locomotor effects of dextromethorphan (0-56.0 mg/kg) using the light-dark and open field tests. Dextromethorphan (32 mg/kg) produced acute (30 min) antidepressant-like effects in TST, but failed to produce antidepressant-like effects 24 h after drug administration. Treatment of dextromethorphan (32 mg/kg) alone or in combination with CYP2D6 enzyme inhibitor Quinidine (32 mg/kg) failed to produce rapid antidepressant-like effects by increasing the latency to drink in the NIH test rather than decreasing the latency to drink. Dextromethorphan (56 mg/kg) produced an anxiogenic-like effect by decreasing the time spent in the light side, number of entries, and latency to enter the light side in the light-dark test. Administration of dextromethorphan (0-56 mg/kg) did not significantly alter locomotor activity. Although dextromethorphan is considered a noncompetitive NMDA receptor antagonist, dextromethorphan binds to several monoaminergic receptors (SERT and NET) and likely produces the antidepressant-like effects through these receptors similar to traditional antidepressant drugs. Additionally, these results suggest that the therapeutic window for dextromethorphan in the clinical population is small as similar doses produce antidepressant-like and anxiogenic-like behaviors.

Physicochemical Evaluation of Compounded Oral Preparations for Respiratory Illnesses, also known as Mezclitas.

OBJECTIVE: Compounded oral solutions for respiratory illnesses such as the common cold and cough are commonly prepared and dispensed by licensed pharmacists in the United States and Puerto Rico (PR). Standard protocols for their preparation and quality assessment and for patient counseling are available for most of the prescribed compounded solutions. However, in PR there is a common prescription approach colloquially referred to as "mezclitas": mixtures of antitussives, expectorants, decongestants, and other active ingredients available in commercial solutions for which there are no science-driven compounding guidelines for local pharmacists. METHODS: This study evaluated the physicochemical stability of a commonly dispensed compounded preparation (containing guaifenesin, dextromethorphan, and dexamethasone) that is used for the treatment of respiratory illnesses in PR. The stability indicators tested included clarity, odor, pH, and viscosity. Changes in stability indicators were evaluated for different storage conditions (ambient temperature and refrigerated) over a period of 6 months. RESULTS: The samples exhibited small changes in color, odor, and viscosity. Although the observed changes were small, they may be indicative of chemical and/or physical transformations that occurred over time. A survey of local pharmacists also evidenced the absence of standardized protocols for the preparation and dispensation of the mezclitas in PR. CONCLUSION: In spite of the absence of protocols for compounding oral solutions for respiratory illnesses, our study suggests that the stability of such solutions is not heavily compromised. However further chemical and physical testing is needed and the findings of such testing used to develop standardized protocols for the compounding of oral solutions for respiratory illnesses.

Subjective features of the psilocybin experience that may account for its self-administration by humans: a double-blind comparison of psilocybin and dextromethorphan.

RATIONALE: Although both psilocybin and dextromethorphan (DXM) produce psychedelic-like subjective effects, rates of non-medical use of psilocybin are consistently greater than DXM. OBJECTIVE: New data are presented from a study of psilocybin and DXM relevant to understanding the features of psilocybin subjective effects that may account for its higher rates of non-medical use. METHODS: Single, acute oral doses of psilocybin (10, 20, 30 mg/70 kg), DXM (400 mg/70 kg), and placebo were administered under double-blind conditions to 20 healthy participants with histories of hallucinogen use. RESULTS: High doses of both drugs produced similar time courses and increases in participant ratings of peak overall drug effect strength. Nine subjective effect domains are proposed to be related to the reinforcing effects of psilocybin: liking, visual effects, positive mood, insight, positive social effects, increased awareness of beauty (both visual and music), awe/amazement, meaningfulness, and mystical experience. For most ratings, (1) psilocybin and DXM both produced effects significantly greater than placebo; (2) psilocybin showed dose-related increases; 3, DXM was never significantly higher than psilocybin; (4) the two highest psilocybin doses were significantly greater than DXM. These differences were consistent with two measures of desire to take the drug condition again. CONCLUSIONS: This analysis provides new information about domains of psilocybin subjective effects proposed to be related to its reinforcing effects (alternatively described as the "motivation" to use). Observed differences on these domains between psilocybin and DXM are consistent with the relative rates of non-medical use of psilocybin and DXM.

Evaluation of hepatic CYP2D1 activity and hepatic clearance in type I and type II diabetic rat models, before and after treatment with insulin and metformin.

INTRODUCTION: Conversion in the metabolism of drugs occurs in diabetes mellitus. Considering the importance of metabolic enzymes' activities on the efficacy and safety of medicines, the changes in liver enzymatic activity of CYP2D1 and its related hepatic clearance, by using Dextromethorphan as probe in the animal model of type I and type II diabetes, before and after treatment, was assessed in this study. METHODS: Male Wistar rats were randomly divided into 6 groups. Seven days after induction of diabetes type I and type II, treatment groups were received insulin and metformin daily for 14 days, respectively. In day 21, rats were subjected to liver perfusion by Krebs-Henseleit buffer containing Dextromethorphan as CYP2D1 probe. Perfusate samples were analyzed by HPLC fluorescence method in order to evaluate any changes in CYP2D1 activity. RESULTS: The average metabolic ratio of dextromethorphan and hepatic clearance were changed from 0.012 ± 0.004 and 6.3 ± 0.1 in the control group to 0.006 ± 0.0008 and 5.2 ± 0.2 in the untreated type I diabetic group, and 0.008 ± 0.003 and 5.0 ± 0.6 in the untreated type II diabetic rats. Finally, the mean metabolic ratio and hepatic clearance were changed to 0.008 ± 0.001 and 5.4 ± 0.1, and 0.013 ± 0.003 and 6.1 ± 0.4 in the treated groups with insulin and metformin, respectively. CONCLUSION: In type I diabetic rats, corresponding treatment could slightly improve enzyme activity, whereas the hepatic clearance and enzyme activity reached to the normal level in type II group. Graphical abstract .

Dextromethorphan and bupropion reduces high level remifentanil self-administration in rats.

Opiate addiction has risen substantially during the past decade. New treatments to combat opiate addiction are sorely needed. The current study was conducted to determine the acute individual and interactive effects of bupropion and dextromethorphan in a rat model of opiate self-administration using the short-acting synthetic opioid remifentanil. Both of these drugs have been found to reduce self-administration of nicotine. Bupropion and dextromethorphan and their combination had differential effects depending on whether the rats showed higher or lower baseline remifentanil self-administration. The rats with higher initial remifentanil self-administration showed a significant decrease in remifentanil self-administration with bupropion or dextromethorphan treatment, compared to the vehicle control condition. This decrease in self-remifentanil administration was most pronounced when combination of the higher doses of bupropion and dextromethorphan were administered. In contrast, the rats with lower baseline remifentanil self-administration showed the opposite effect of drug treatment with an increase in remifentanil self-administration with bupropion treatment compared to the vehicle control condition. Dextromethorphan had no significant effect inthis group. This study shows that combination bupropion and dextromethorphan affects remifentanil self-administration in a complex fashion with differential effects on low and high baseline responders. In subjects with high baseline remifentanil self-administration, bupropion and dextromethorphan treatment significantly reduced self-administration, whereas in subjects with low baseline remifentanil self-administration, bupropion increased remifentanil self-administration and dextromethorphan had no discernible effect. This finding suggests that combination bupropion-dextromethorphan should be tested in humans, with a focus on treating people with high-level opiate use.

Effects of Maribavir on P-Glycoprotein and CYP2D6 in Healthy Volunteers.

Maribavir is an investigational drug being evaluated in transplant recipients with cytomegalovirus infection. To understand potential drug-drug interactions, we examined the effects of multiple doses of maribavir on cytochrome P450 (CYP) 2D6 and P-glycoprotein (P-gp) activity using probe substrates in healthy volunteers. During this phase 1 open-label study (NCT02775240), participants received the probe substrates digoxin (0.5 mg) and dextromethorphan (30 mg) before and after maribavir (400 mg twice daily for 8 days). Serial plasma samples were analyzed for digoxin, dextromethorpha, dextrorphan, and maribavir concentrations. Pharmacokinetic parameters were calculated (noncompartmental analysis) and analyzed with a linear mixed-effects model for treatment comparison to estimate geometric mean ratios (GMRs) and 90% confidence intervals (CIs). CYP2D6 polymorphisms were genotyped using polymerase chain reaction. Overall, 17 of 18 participants (94.4%) completed the study. All participants were genotyped as CYP2D6 intermediate/extensive metabolizers. GMR (90%CI) of digoxin Cmax , AUClast , and AUC0-∞ with and without maribavir was 1.257 (1.139-1.387), 1.187 (1.088-1.296), and 1.217 (1.110-1.335), respectively, outside the "no-effect" window (0.8-1.25). GMR (90%CI) of dextromethorphan AUClast and AUClast ratio of dextromethorphan/dextrorphan were 0.877 (0.692-1.112) and 0.901 (0.717-1.133), respectively, marginally outside the no-effect window, although large variability was observed in these pharmacokinetic parameters. Pharmacokinetic parameters of dextrorphan were unaffected. Maribavir inhibited P-gp activity but did not affect CYP2D6 activity. Maribavir's effect on the pharmacokinetics of P-gp substrates should be evaluated individually, and caution should be exercised with P-gp substrates with narrow therapeutic windows.

Effects of Upadacitinib Coadministration on the Pharmacokinetics of Sensitive Cytochrome P450 Probe Substrates: A Study With the Modified Cooperstown 5+1 Cocktail.

The aim of this study was to characterize the effects of upadacitinib, a Janus kinase 1 inhibitor, on in vivo activity of different cytochrome P450 (CYP) enzymes using a cocktail approach. Healthy subjects (n = 20) received single oral doses of the modified Cooperstown 5+1 cocktail drugs (midazolam [CYP3A], caffeine [CYP1A2], warfarin + vitamin K [CYP2C9], omeprazole [CYP2C19], and dextromethorphan [CYP2D6]) without upadacitinib and on day 11 (midazolam) or 12 (all other probes) of a 15-day regimen of upadacitinib 30 mg once daily (extended-release formulation). Serial blood samples and 12-hour urine samples were collected for assays of the probe substrates and select metabolites. The ratio (90%CI) of area under the plasma concentration-time curve from time 0 to infinity (AUCinf ) central values when the cocktail drugs were administered with upadacitinib relative to when administered alone were 0.74 (0.68-0.80) for midazolam, 1.22 (1.15-1.29) for caffeine, 1.11 (1.07-1.15) for S-warfarin, 1.07 (0.95-1.22) for dextromethorphan, and 0.82 (0.72-0.94) for omeprazole. The ratio (90%CI) was 1.09 (1.00-1.19) for 5-hydroxy-omeprazole to omeprazole AUCinf ratio and 1.17 (0.97-1.41) for dextromethorphan to dextrorphan 12-hour molar urinary ratio. Upadacitinib 30 mg once daily (a dose that is twice the optimal dose in rheumatoid arthritis based on phase 3 results) has a limited effect on CYP3A activity (26% decrease in exposure of midazolam, a sensitive CYP3A substrate) and no relevant effects on CYP1A2, CYP2C9, CYP2C19, or CYP2D6 activity in vivo. No clinically relevant changes in plasma exposures are expected for drugs that are substrates for the evaluated CYP enzymes when coadministered with upadacitinib.

Medication Errors From Over-the-Counter Cough and Cold Medications in Children.

OBJECTIVE: Out of hospital medication-related adverse events (AEs) from cough and cold medications (CCMs) can have significant public health impact. The objective of this study was to characterize pediatric medication error AEs involving over-the-counter (OTC) CCMs to identify preventable factors. METHODS: Multisource national data surveillance system study using an expert panel evaluating CCM AEs related to medication errors. INCLUSION CRITERIA: age <12 years, and at least 1 significant AE from at least 1 index ingredient from a CCM OTC product. RESULTS: From 2009 through 2016, 4756 cases were determined to have a significant AE related to an OTC CCM ingredient and 513 (10.8%) cases were due to a medication error. Nearly half of medication errors involved children 2 to <6 years old (n = 235; 45.8%). Many involved administration by a parent (n = 231; 45.0%) or alternative caregiver (n = 148; 28.8%). In nearly all cases (93.2%), the medication error involved the wrong dose of the medication. Health care facility evaluation occurred in 381 (74.3%) cases. Diphenhydramine and dextromethorphan were responsible for most medication errors and medication errors involving health care facility evaluation. There were no deaths from medication errors. CONCLUSION: In this multiyear surveillance study, medication errors most commonly occurred in children <6 years old who received the wrong volume of a liquid product. Diphenhydramine and dextromethorphan dosing errors were the most common cause of medication errors resulting from CCM use. Continued standardization of measuring devices, concentrations, and units of measure along with consumer education are needed to further decrease medication errors from CCMs.