Gut microbiota biotransformation of drug glucuronides leading to gastrointestinal toxicity: Therapeutic potential of bacterial ß-glucuronidase inhibition in mycophenolate-induced enteropathy.

AIMS: Drug-induced enteropathy is often associated with the therapeutic use of certain glucuronidated drugs. One such drug is mycophenolic acid (MPA), a well-established immunosuppressant of which gastrointestinal adverse effects are a major concern. The role of bacterial ß-glucuronidase (ß-G) from the gut microbiota in MPA-induced enteropathy has recently been discovered. Bacterial ß-G hydrolyzes MPAG, the glucuronide metabolite of MPA excreted in the bile, leading to the digestive accumulation of MPA that would favor in turn these adverse events. We therefore hypothesized that taming bacterial ß-G activity might reduce MPA digestive exposure and prevent its toxicity. MAIN METHODS: By using a multiscale approach, we evaluated the effect of increasing concentrations of MPA on intestinal epithelial cells (Caco-2 cell line) viability, proliferation, and migration. Then, we investigated the inhibitory properties of amoxapine, a previously described bacterial ß-G inhibitor, by using molecular dynamics simulations, and evaluated its efficiency in blocking MPAG hydrolysis in an Escherichia coli-based ß-G activity assay. The pharmacological effect of amoxapine was evaluated in a mouse model. KEY FINDINGS: We observed that MPA impairs intestinal epithelial cell homeostasis. Amoxapine efficiently blocks the hydrolysis of MPAG to MPA and significantly reduces digestive exposure to MPA in mice. As a result, administration of amoxapine in MPA-treated mice significantly attenuated gastrointestinal lesions. SIGNIFICANCE: Collectively, these results suggest that the digestive accumulation of MPA is involved in the pathophysiology of MPA-gastrointestinal adverse effects. This study provides a proof-of-concept of the therapeutic potential of bacterial ß-G inhibitors in glucuronidated drug-induced enteropathy.

Amoxapine-Loaded Solid Lipid Nanoparticles with Superior Preclinical Pharmacokinetics for Better Brain Delivery: LC-MS/MS and GC-MS Analysis.

The tricyclic antidepressant amoxapine (AMX) has been reported for a rapid onset of action compared to other cyclic antidepressants. It has very low solubility and bioavailability due to first-pass metabolism. Therefore, we planned to develop solid lipid nanoparticles (SLNs) of AMX using a single emulsification method to increase its solubility and bioavailability. HPLC and LC-MS/MS methods were developed further to quantify AMX in the formulation, plasma, and brain tissue samples. The formulation was studied for entrapment efficiency, loading, and in vitro drug release. Particle size and ζ potential analyses, AFM, SEM, TEM, DSC, and XRD were used for further characterization. In vivo oral pharmacokinetic and brain pharmacokinetic studies were performed using Wistar rats. The entrapment and loading efficiencies of AMX in SLNs were 85.8 ± 3.42 and 4.5 ± 0.45%, respectively. The developed formulation had a mean particle size of 151.5 ± 7.02 nm and a polydispersity index of 0.40 ± 0.11. DSC and XRD results indicated that AMX was incorporated into the nanocarrier system in an amorphous form. SEM, TEM, and AFM studies of AMX-SLNs confirmed the particles' spherical shape and nanoscale size. AMX solubility increased by approx. 2.67 times compared to the pure drug. The developed LC-MS/MS method was successfully applied to the oral and brain pharmacokinetic study of AMX-loaded SLNs in rats. Oral bioavailability was enhanced 1.6 times compared to the pure drug. The peak plasma concentrations of pure AMX and AMX-SLNs were 617.4 ± 137.4 and 1043.5 ± 150.2 (ng/mL), respectively. AMX-SLNs showed more than 5.8 times brain concentration compared to the pure drug. Based on the findings, it appears that utilizing a solid lipid nanoparticle carrier to transport AMX can be a highly effective delivery method with improved pharmacokinetic properties in the brain. This approach may prove valuable for future antidepressant treatment.

GABAA receptor-mediated seizure liabilities: a mixed-methods screening approach.

GABAA receptors, members of the pentameric ligand-gated ion channel superfamily, are widely expressed in the central nervous system and mediate a broad range of pharmaco-toxicological effects including bidirectional changes to seizure threshold. Thus, detection of GABAA receptor-mediated seizure liabilities is a big, partly unmet need in early preclinical drug development. This is in part due to the plethora of allosteric binding sites that are present on different subtypes of GABAA receptors and the critical lack of screening methods that detect interactions with any of these sites. To improve in silico screening methods, we assembled an inventory of allosteric binding sites based on structural data. Pharmacophore models representing several of the binding sites were constructed. These models from the NeuroDeRisk IL Profiler were used for in silico screening of a compiled collection of drugs with known GABAA receptor interactions to generate testable hypotheses. Amoxapine was one of the hits identified and subjected to an array of in vitro assays to examine molecular and cellular effects on neuronal excitability and in vivo locomotor pattern changes in zebrafish larvae. An additional level of analysis for our compound collection is provided by pharmacovigilance alerts using FAERS data. Inspired by the Adverse Outcome Pathway framework, we postulate several candidate pathways leading from specific binding sites to acute seizure induction. The whole workflow can be utilized for any compound collection and should inform about GABAA receptor-mediated seizure risks more comprehensively compared to standard displacement screens, as it rests chiefly on functional data.

Successful Treatment of Amoxapine-Induced Intractable Seizures With Intravenous Lipid Emulsion.

BACKGROUND: Amoxapine is a second-generation tricyclic antidepressant with a greater seizure risk than other antidepressants. If administered in large amounts, amoxapine can cause severe toxicity and death. Therefore, it is necessary to terminate seizures immediately if amoxapine toxicity occurs. However, intractable seizures often occur in these patients. We describe a case of intractable seizures caused by amoxapine poisoning, in which intravenous lipid emulsion (ILE) was used successfully. CASE REPORT: A 44-year-old woman with a history of depression ingested 3.0 g of amoxapine during a suicide attempt. Although she was initially treated with intravenous diazepam, her seizures persisted. Levetiracetam and phenobarbital were then administered, but seizures persisted. Hence, ILE was injected for over 1 min. At 2 min after ILE administration, the patient's status seizures ceased. Recurrence of seizures was observed 30 min after ILE, and the seizures disappeared after re-administration of ILE. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: ILE may be effective in amoxapine intoxication. Emergency physicians may consider ILE as an adjunctive therapy for amoxapine poisoning with a high mortality rate. ILE should be implemented carefully with monitoring of total dosage and adverse events.

Toxicokinetic evaluation during intoxication of psychotropic drugs using brain microdialysis in mice.

In the event of an overdose, the pharmacokinetics of the drug may be altered, resulting in an unexpectedly rapid increase in blood and tissue drug concentrations. Because central nervous system (CNS)-acting drugs are the major cause of hospitalization for overdose, brain concentrations, which are closely related to the development of acute psychotropic symptoms, would be important. However, due to the lack of an appropriate model for overdose, it is difficult to predict the CNS symptoms of patients with acute poisoning. To clarify the toxicokinetics during intoxication with CNS-acting drugs, we investigated the relationship between the dose and concentrations in the blood and brain in mice. Therapeutic or toxic doses of phenobarbital, flunitrazepam, imipramine, and amoxapine were administered intraperitoneally to mice. Serum and extracellular fluid of the brain were collected up to 24 hr after administration and analyzed using LC-MS/MS to determine the pharmacokinetic parameters in the serum and brain. A comparison of the four psychotropic drugs showed that the toxicokinetics of amoxapine in the blood and brain are clearly different from others, with the brain concentrations being specifically highly susceptible to increase during dose escalation. These results are consistent with the CNS-related symptoms observed in amoxapine overdose. Therefore, the methodology of the current study could be useful for predicting CNS toxicity during psychotropic drug poisoning.

Phenelzine and Amoxapine Inhibit Tyramine and d-Glucuronic Acid Catabolism in Clinically Significant Salmonella in A Serotype-Independent Manner.

Non-typhoidal Salmonella ingeniously scavenges energy for growth from tyramine (TYR) and d-glucuronic acid (DGA), both of which occur in the host as the metabolic byproducts of the gut microbial metabolism. A critical first step in energy scavenging from TYR and DGA in Salmonella involves TYR-oxidation via TYR-oxidoreductase and production of free-DGA via ß-glucuronidase (GUS)-mediated hydrolysis of d-glucuronides (conjugated form of DGA), respectively. Here, we report that Salmonella utilizes TYR and DGA as sole sources of energy in a serotype-independent manner. Using colorimetric and radiometric approaches, we report that genes SEN2971, SEN3065, and SEN2426 encode TYR-oxidoreductases. Some Salmonella serotypes produce GUS, thus can also scavenge energy from d-glucuronides. We repurposed phenelzine (monoaminoxidase-inhibitor) and amoxapine (GUS-inhibitor) to inhibit the TYR-oxidoreductases and GUS encoded by Salmonella, respectively. We show that phenelzine significantly inhibits the growth of Salmonella by inhibiting TYR-oxidoreductases SEN2971, SEN3065, and SEN2426. Similarly, amoxapine significantly inhibits the growth of Salmonella by inhibiting GUS-mediated hydrolysis of d-glucuronides. Because TYR and DGA serve as potential energy sources for Salmonella growth in vivo, the data and the novel approaches used here provides a better understanding of the role of TYR and DGA in Salmonella pathogenesis and nutritional virulence.

Elucidation of Degradation Behavior of Tricyclic Antidepressant Amoxapine in Artificial Gastric Juice.

The degradation behavior of eight tricyclic antidepressants (TCAs; amitriptyline, amoxapine (AMX), imipramine, clomipramine, desipramine, doxepin, dothiepin, and nortriptyline) in artificial gastric juice was investigated to estimate their pharmacokinetics in the stomach. As a result, among the eight TCAs, only AMX was degraded in artificial gastric juice. The degradation was a pseudo first-order reaction; activation energy (Ea) was 88.70 kJ/mol and activation entropy (ΔS) was -80.73 J/K·mol. On the other hand, the recovery experiment revealed that the degradation product did not revert to AMX and accordingly, this reaction was considered to be irreversible. In the AMX degradation experiment, peaks considered to be degradation products A (I) and B (II) were detected at retention times of around 3 min and 30 min in LC/UV measurements, respectively. Structural analysis revealed that compound (I) was [2-(2-aminophenoxy)-5-chlorophenyl]-piperazin-1-yl-methanone, a new compound, and compound (II) was 2-chlorodibenzo[b,f][1,4]oxazepin-11(10H)-one. As for the degradation behavior, it was estimated that AMX was degraded into (II) via (I), i.e., (II) was the final product. The results are expected to be useful in clinical chemistry and forensic science, including the estimation of drugs to be used at the time of judicial dissection and suspected drug addiction.

A mitochondria-selective near-infrared-emitting fluorescent dye for cellular imaging studies.

This communication details the synthesis, evaluation of photophysical properties, and cellular imaging studies of cyanine chromophore based fluorescent dye 1 as a selective imaging agent for mitochondria.

Amoxapine Demonstrates Incomplete Inhibition of ß-Glucuronidase Activity from Human Gut Microbiota.

Amoxapine has been demonstrated to be a potent inhibitor of Escherichia coli ß-glucuronidase. This study aims to explore the factors causing unsatisfactory efficacy of amoxapine in alleviating CPT-11-induced gastrointestinal toxicity in mice and to predict the outcomes in humans. Amoxapine (100 µM) exhibited poor and varied inhibition on ß-glucuronidase activity in gut microbiota from 10 healthy individuals and their pool (pool, 11.9%; individuals, 3.6%-54.4%) with IC50 >100 µM and potent inhibition toward E. coli ß-glucuronidase (IC50 = 0.34 µM). p-Nitrophenol formation from p-nitrophenyl-ß-D-glucuronide by pooled and individual gut microbiota fitted classical Michaelis-Menten kinetics, showing similar affinity (Km = 113-189 µM) but varied catalytic capability (Vmax = 53-556 nmol/h/mg). Interestingly, amoxapine showed distinct inhibitory effects (8.7%-100%) toward ß-glucuronidases of 13 bacterial isolates (including four Enterococcus, three Streptococcus, two Escherichia, and two Staphylococcus strains; gus genes belonging to OTU1, 2 or 21) regardless of their genetic similarity or bacterial origin. In addition, amoxapine inhibited the growth of pooled and individual gut microbiota at a high concentration (6.3%-30.8%, 200 µM). Taken together, these findings partly explain the unsatisfactory efficacy of amoxapine in alleviating CPT-11-induced toxicity and predict a poor outcome of ß-glucuronidase inhibition in humans, highlighting the necessity of using a human gut microbiota community for drug screening.

Randomized crossover trial of amoxapine versus vitamin B12 for retrograde ejaculation

ABSTRACT Objective To compare the efficacy and safety of amoxapine and vitamin B12 for treating retrograde ejaculation (RE). Materials and Methods Between May 2009 and November 2012, this open-label, randomized, crossover study enrolled 26 men suffering with RE at Department of Reproductive Medicine, Omori Hospital. Patients were randomly allocated into two groups (n=13 each). The amoxapine-B12 group received amoxapine (50 mg daily for 4 weeks, orally) followed (after a 1-week washout period) by vitamin B12 (500 μg three-times daily for 4 weeks). The B12-amoxapine group received the opposite regimen. All patients masturbated to ejaculation at least twice during each treatment period. The primary outcome was antegrade ejaculation of semen, as reported by the patient, on more than one occasion during either treatment period (defined as treatment success). Any adverse events were noted. Success rates were compared between treatments using Fisher’s exact test. Results One patient (B12-amoxapine group) withdrew for personal reasons (breakdown of marital relations); all other patients completed the study. Overall success rate was 88% (22/25). Success rate was higher for amoxapine than for vitamin B12 (80%, 20/25 vs 16%, 4/25; P<0.0001). 18 patients were responsive to amoxapine but not to vitamin B12, 2 patients were responsive to vitamin B12 but not amoxapine, 2 patients were responsive to both drugs, and 3 patients had no response to either drug. One patient (4%) reported sleepiness and 2 (8%) reported constipation while receiving amoxapine. No adverse events were reported during vitamin B12 treatment. Conclusions Amoxapine may be an effective, safe and well-tolerated therapy for RE.

Crystal structure of a mixed solvated form of amoxapine acetate.

The mixed solvated salt 4-(2-chloro-dibenzo[b,f][1,4]oxazepin-11-yl)piperazin-1-ium acetate-acetic acid-cyclo-hexane (2/2/1), C17H17ClN3O(+)·C2H3O2 (-)·C2H4O2·0.5C6H12, crystallizes with one mol-ecule of protonated amoxapine (AXPN), an acetate anion and a mol-ecule of acetic acid together with half a mol-ecule of cyclo-hexane. In the centrosymmetric crystal, both enanti-omers of the protonated AXPN mol-ecule stack alternatively along [001]. Acetate anions connect the AXPN cations through N-H⋯O hydrogen bonding in the [010] direction, creating a sheet lying parallel to (100). The acetic acid mol-ecules are linked to the acetate anions via O-H⋯O hydrogen bonds within the sheets. Within the sheets there are also a number of C-H⋯O hydrogen bonds present. The cyclo-hexane solvent mol-ecules occupy the space between the sheets.

Serotonin syndrome caused by interaction between fentanyl and amoxapine in a patient with cancer pain

<b>Objective</b>:To report a case of serotonin syndrome induced by an interaction between fentanyl and amoxapine in a patient treated for cancer pain. <b>Case:A</b> 37-year-old woman with recurrence of cervical cancer was treated with oxycodone and etodolac for her cancer pain in the gluteal region. She developed acute abdominal pain and received emergency surgery under the diagnosis of upper gastrointestinal tract perforation.Continuous fentanyl infusion was initiated during surgery and was continued postoperatively to control postsurgical and cancer pain. The route of fentanyl was changed to transdermal patch the next day, and dose was escalated during the following days in attempt to control her gluteal pain. Eight days after the operation, amoxapine was prescribed as an adjuvant analgesic. Five days later, the fentanyl dose was further escalated to 2100μg/day. The following day, the patient developed tremors of the extremities, confusion and hallucinations, followed by fever and involuntary movements of the lower extremities. Amoxapine was discontinued and the symptoms subsided within 4 days.<b>Conclusion</b>:Co-administration of a tricyclic antidepressant and high doses of fentanyl precipitated serotonin syndrome in this patient.

Successful management of rectal tenesmus with oral amoxapine and infusional lidocaine in a terminally ill cancer patient：a case report and literature review

Background: Although rectal tenesmus in patients with advanced cancer can have marked negative impact on quality of life, effective treatment has not yet been established. Case: A 71 -year-old man with an inoperable rectal cancer developed tenesmus 11 months after a colostomy. Tenesmus worsened over the following 3 months, and the patient suffered from involuntary straining every 5-15 minutes. After unsuccessful symptom control with radiotherapy to the primary lesion, we started oral amoxapine 25 mg that alleviated symptoms related to tenesmus. As the general condition deteriorated, however, oral intake became difficult. After the discontinuation of amoxapine, the tenesmus recurred even though intravenous administration of clomipramine was initiated. We started continuous infusion of intravenous lidocaine 200 mg/day which successfully relieved tenesmus. The dose of lidocaine was subsequently increased to 290 mg/day for worsening symptoms, which continued to control his distress caused by tenesmus until he died. Consideration/Conclusion: This is the first report that demonstrates the efficacy of oral amoxapine for rectal tenesmus with malignant tumor. After the discontinuation of amoxapine due to the inability of taking medications orally, symptoms remained under adequate control with infusional lidocaine until the patient died. Further studies are warranted to confirm our findings and to propose optimal use of medications in the management of rectal tenesmus.

Successful treatment of rhabdomyolysis and acute renal failure following amoxapine overdose.

Amoxapine, a tricyclic antidepressant, is widely used by psychiatrists. While overdose of tricyclic antidepressants is known to be dangerous and potentially fatal (causing hypotension, arrhythmia, convulsions, respiratory failure, and other serious complications), overdose of amoxapine can cause other problems, and metabolic acidosis, seizures, neuroleptic malignant syndrome, and arrhythmia have been reported. This report describes the case of a patient who developed rhabdomyolysis and acute renal failure following amoxapine overdose. Continuous hemofiltration was instituted twice, and he recovered without sequelae; this suggests the effectiveness of continuous hemofiltration and its possibilities in the treatment of amoxapine overdose and acute renal failure due to rhabdomyolysis.