Classics in Chemical Neuroscience: Selegiline, Isocarboxazid, Phenelzine, and Tranylcypromine.

The discovery of monoamine oxidase inhibitors (MAOIs) in the 1950s marked a significant breakthrough in medicine, creating a powerful new category of drug: the antidepressant. In the years and decades that followed, MAOIs have been used in the treatment of several pathologies including Parkinson's disease, Alzheimer's disease, and various cancers and as anti-inflammatory agents. Despite once enjoying widespread use, MAOIs have dwindled in popularity due to side effects, food-drug interactions, and the introduction of other antidepressant drug classes such as tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs). The recently published prescriber's guide for the use of MAOIs in treating depression has kindled a resurgence of their use in the clinical space. It is therefore timely to review key aspects of the four "classic" MAOIs: high-dose selegiline, isocarboxazid, phenelzine, and tranylcypromine. This review discusses their chemical synthesis, metabolism, pharmacology, adverse effects, and the history and importance of these drugs within the broader field of chemical neuroscience.

Treatment History Characteristics Associated With Use of Isocarboxazid: A Nationwide Register-Based Study.

PURPOSE/BACKGROUND: The monoamine oxidase inhibitor isocarboxazid (Marplan) is occasionally used in the treatment of depression, but there is only little knowledge on the nature of the use of isocarboxazid in clinical practice. We aimed to identify treatment history characteristics associated with this use. METHODS/PROCEDURES: Via the nationwide Danish registers, we identified all adult incident users of isocarboxazid in the period from 2001 to 2018, as well as up to 5 matched controls using another antidepressant (matched on date of redeemed prescription, age, sex, and region of residence). The 5-year treatment history of the isocarboxazid users and the controls was assessed via the Danish registers. The association between treatment history characteristics and isocarboxazid use was examined by multivariate conditional logistic regression. FINDINGS/RESULTS: We identified 1455 isocarboxazid users and 7045 controls using another antidepressant. The following characteristics were associated with statistically significant increased likelihood of receiving isocarboxazid treatment: Prior treatment with a selective serotonin reuptake inhibitor (odds ratio [OR], 1.80 with 95% confidence interval [CI], 1.46-2.23), a serotonin-norepinephrine reuptake inhibitor (OR, 4.90; 95% CI, 4.08-5.89), a noradrenergic and specific serotonergic antidepressant (OR, 1.56; 95% CI, 1.30-1.88), a tricyclic antidepressant (OR, 5.05; 95% CI, 4.19-6.08), other antidepressants (OR, 4.74; 95% CI, 3.74-6.01), lithium (OR, 6.70; 95% CI, 5.08-8.83), an antipsychotic (OR, 1.43; 95% CI, 1.19-1.73), and each diagnosis of depression received in relation to psychiatric hospital treatment (OR, 1.31; 95% CI, 1.23-1.39). Forty percent of those initiating isocarboxazid had received treatment with drugs from 5 or more different psychopharmacological classes in the 5 preceding years. IMPLICATIONS/CONCLUSIONS: These findings suggest that isocarboxazid is typically used for treatment-resistant depression, consistent with guideline recommendations.

Anticholinergic medication for antipsychotic-induced tardive dyskinesia.

BACKGROUND: Antipsychotic (neuroleptic) medication is used extensively to treat people with serious mental illnesses. However, it is associated with a wide range of adverse effects, including movement disorders. Because of this, many people treated with antipsychotic medication also receive anticholinergic drugs in order to reduce some of the associated movement side-effects. However, there is also a suggestion from animal experiments that the chronic administration of anticholinergics could cause tardive dyskinesia. OBJECTIVES: To determine whether the use or the withdrawal of anticholinergic drugs (benzhexol, benztropine, biperiden, orphenadrine, procyclidine, scopolamine, or trihexylphenidyl) are clinically effective for the treatment of people with both antipsychotic-induced tardive dyskinesia and schizophrenia or other chronic mental illnesses. SEARCH METHODS: We retrieved 712 references from searching the Cochrane Schizophrenia Group's Study-Based Register of Trials including the registries of clinical trials (16 July 2015 and 26 April 2017). We also inspected references of all identified studies for further trials and contacted authors of trials for additional information. SELECTION CRITERIA: We included reports identified in the search if they were controlled trials dealing with people with antipsychotic-induced tardive dyskinesia and schizophrenia or other chronic mental illness who had been randomly allocated to (a) anticholinergic medication versus placebo (or no intervention), (b) anticholinergic medication versus any other intervention for the treatment of tardive dyskinesia, or (c) withdrawal of anticholinergic medication versus continuation of anticholinergic medication. DATA COLLECTION AND ANALYSIS: We independently extracted data from included trials and we estimated risk ratios (RR) with 95% confidence intervals (CIs). We assumed that people who left early had no improvement. We assessed risk of bias and created a 'Summary of findings' table using GRADE. MAIN RESULTS: The previous version of this review included no trials. We identified two trials that could be included from the 2015 and 2017 searches. They randomised 30 in- and outpatients with schizophrenia in the USA and Germany. Overall, the risk of bias was unclear, mainly due to poor reporting: allocation concealment was not described; generation of the sequence was not explicit; studies were not clearly blinded; and outcome data were not fully reported.Findings were sparse. One study reported on the primary outcomes and found that significantly more participants allocated to procyclidine (anticholinergic) had not improved to a clinically important extent compared with those allocated to isocarboxazid (MAO-inhibitor) after 40 weeks' treatment (1 RCT, n = 20; RR 4.20, 95% CI 1.40 to 12.58; very low quality evidence); that there was no evidence of a difference in the incidence of any adverse effects (1 RCT, n = 20; RR 0.33, 95% CI 0.02 to 7.32; very low quality evidence); or acceptability of treatment (measured by participants leaving the study early) (1 RCT, n = 20; RR 0.33, 95% CI 0.02 to 7.32; very low quality evidence). The other trial compared anticholinergic withdrawal with anticholinergic continuation and found no evidence of a difference in the incidence of acceptability of treatment (measured by participants leaving the study early) (1 RCT, n = 10; RR 2.14, 95% CI 0.11 to 42.52; very low quality evidence).No trials reported on social confidence, social inclusion, social networks, or personalised quality of life - outcomes designated important to patients. No studies comparing either i. anticholinergics with placebo or no treatment, or ii. studies of anticholinergic withdrawal, were found that reported on the primary outcome 'no clinically important improvement in TD symptoms and adverse events'. AUTHORS' CONCLUSIONS: Based on currently available evidence, no confident statement can be made about the effectiveness of anticholinergics to treat people with antipsychotic-induced tardive dyskinesia. The same applies for the withdrawal of such medications. Whether the withdrawal of anticholinergics may benefit people with antipsychotic-induced TD should be evaluated in a parallel-group, placebo-controlled randomised trial, with adequate sample size and at least 6 weeks of follow-up.

[The use of the monoamine oxidase inhibitor isocarboxazide in treatment-resistant depression]. / Anvendelse af monoaminooksidasehæmmeren isocarboxazid ved behandlingsresistent depression

The antidepressant efficacy of isocarboxazide is well established; however, the clinical use early became restricted and today the use of isocarboxazide in Denmark is very limited. Isocarboxazide is safe when keeping a low tyramine-containing diet and avoiding concomitant treatment with certain drugs. The risk of developing oedema can be reduced by vitamin B6 treatment. Normal dosage isocarboxazide may be prescribed for all patients because isocarboxazide is not metabolized through the CYP2D6 enzyme complex like most other antidepressants. It is recommended to include isocarboxazide in the official treatment algorithms for patients who are resistant to conventional antidepressant therapy and electroconvulsive therapy.

Potential repurposing of known drugs as potent bacterial ß-glucuronidase inhibitors.

The active metabolite of the chemotherapeutic irinotecan, SN-38, is detoxified through glucuronidation and then excreted into the gastrointestinal tract. Intestinal bacteria convert the glucuronidated metabolite back to the toxic SN-38 using ß-glucuronidase (GUS), resulting in debilitating diarrhea. Inhibiting GUS activity may relieve this side effect of irinotecan. In this study, we sought to determine whether any known drugs have GUS inhibitory activity. We screened a library of Food and Drug Administration-approved drugs with a cell-free biochemical enzyme assay using purified bacterial GUS. After triage, five drugs were confirmed to inhibit purified bacterial GUS. Three of these were the monoamine oxidase inhibitors nialamide, isocarboxazid, and phenelzine with average IC(50) values for inhibiting GUS of 71, 128, and 2300 nM, respectively. The tricyclic antidepressant amoxapine (IC(50) = 388 nM) and the antimalarial mefloquine (IC(50) = 1.2 µM) also had activity. Nialamide, isocarboxazid, and amoxapine had no significant activity against purified mammalian GUS but showed potent activity for inhibiting endogenous GUS activity in a cell-based assay using living intact Escherichia coli with average IC(50) values of 17, 336, and 119 nM, respectively. Thus, nialamide, isocarboxazid, and amoxapine have potential to be repurposed as therapeutics to reduce diarrhea associated with irinotecan chemotherapy and warrant further investigation for this use.

[Irreversible, non-selective monoamine oxidase inhibitors]. / Irreversible, uselektive monoaminoksidasehemmere.

Irreversible, non-selective monoamine oxidase (MAO) inhibitors were among the first antidepressants. No drugs in this group are currently marketed in Norway, but many physicians will see patients using them, as they can be prescribed on a named patient basis after application to the Norwegian Medicines Agency. This article presents adverse effects, interactions and precautions related to the use of these drugs.

Synthesis of novel N-substituted imidazolecarboxylic acid hydrazides as monoamine oxidase inhibitors.

Novel 2-alkylsulfanyl-1-benzyl-5-imidazolecarboxylic acid hydrazides (15a,b) were synthesized as analogues of isocarboxazide, which is a known nonselective irreversible monoamine oxidase inhibitor and tested for monoamine oxidase A and B inhibitory activity. Neither of the compounds showed any inhibition of MAO B activity up to a high concentration of 100 microM. An MAO A activity was only slowly inhibited at this high concentration after prolonged incubation with either compound. This suggests any observed inhibition is not very specific.

[Prolonged hyperthermia after isocarboxazid poisoning]. / Langvarig hypertermi efter isocarboxazidforgiftning.

A 44-year-old unconscious man was admitted 24 hours after intake of approximately one gram of isocarboxazid. He was subsequently intubated for seven days. Muscular hyperactivity and prolonged hyperthermia were the main therapeutic problems which were treated with dantrolene, levomepromazine, pancuronium, and external cooling. Massive rhabdomyolysis was treated with forced diuresis.

Characterization of eprinomectin N-deacetylase in rats.

The enzyme system responsible for the N-deacetylation of eprinomectin in rats was characterized. Tissue and subcellular studies showed that the hydrolysis activity was localized mainly in liver microsomes. Apparent KM and Vmax values calculated from Lineweaver-Burk plots were 53 microM and 0.81 nmol/mg/min for male rats and 70 microM and 4.99 nmol/mg/min for female rats, respectively. Pretreatment of male rats with dexamethasone, phenobarbital, and pregnenolone 16alpha-carbonitrile increased the activity by more than 3-fold. Paraoxon and bis-4-nitrophenylphosphate strongly inhibited the deacetylase activity at concentrations as low as 1 microM. The hydrolysis activity also was inhibited by SKF525, but less effectively. Eserine strongly inhibited the activity at 1 x 10(-4) M. HgCl2 decreased the activity to about 40% at a concentration of 1 x 10(-4) M. FeCl3, CaCl2, MgCl2, and EDTA had little effect on the hydrolysis of eprinomectin, whereas NaF slightly increased the activity to 118%. Thus, the inhibition study suggested that eprinomectin deacetylase resembled "B" type carboxylesterase/amidases. The hydrolysis activity of eprinomectin and isocarboxazid, a specific substrate of RL2 [Hosokawa, M, Maki T and Satoh T (1987) Mol Pharmacol 31:579-584], by liver microsomes from rats treated with various cytochrome P-450 inducers correlated well (r = 0.92). Also, elusion profiles of esterase by gel filtration and ion exchange chromatography demonstrated that the active protein(s) for eprinomectin and isocarboxazid hydrolysis coeluted. Thus, RL2 or an enzyme system similar to RL2 is responsible for the N-deacetylation of eprinomectin.

The Major Depression Rating Scale (MDS). Inter-rater reliability and validity across different settings in randomized moclobemide trials. Danish University Antidepressant Group.

The Major Depression Rating Scale (MDS) has been derived from the Hamilton Depression Scale and the Melancholia Scale. The MDS contains the nine DSM-IV items for major depression which all have anchoring scores from 0 to 4; hence, the theoretical score range is up to 36. The Major Depression Rating Scale has in this study been psychometrically analysed in randomized moclobemide trials. The results showed that the MDS had higher internal validity than the Hamilton Depression Scale. Thus, the homogeneity of the items was higher; factor analysis identified only one general depression factor (after 4 weeks of treatment explaining more than 50% of the variance). The inter-rater reliability of the two scales was of the same high level. The ability to measure changes (external validity) was tested in randomized clinical trials with moclobemide versus tricyclics (clomipramine and notriptyline) performed in Denmark in the psychiatric setting as well as in the general practice. The results showed that in the psychiatric setting tricyclics were superior to moclobemide with effect sizes ranging between 0.43 and 0.53. The highest effect size was obtained with the Melancholia Scale and the Major Depression Rating Scale, while the Hamilton Depression Scale was below 0.50. In the general practice setting no difference was found between moclobemide and clomipramine. In conclusion, the Major Depression Rating Scale has been found to have a more homogeneous factor structure than the Hamilton Depression Scale, but still with the same level of reliability and external validity. However, studies are needed to standardize the scale, especially in the general practice setting.

A 3-year follow-up of a group of treatment-resistant depressed patients with a MAOI/tricyclic combination.

Treatment-resistant depression is a clinical complication that not infrequently affects a certain number of patients. Within the treatment strategies proposed for this condition, the association of a MAO inhibitor (MAOI) with a tricyclic antidepressant has gained reputation both for its unusual efficacy, as for its potential toxicity. However, when cautions are taken, it may be safely administered. Most reports on this combination have been carried in nonresistant patients and, when resistant patients are included, only the acute phase of the treatment is reported. In this study, a group of well-defined resistant patients received an open trial with the association of isocarboxazide and amitryptiline (n = 25). Those who responded were followed during the next 3 years (n = 12) and every 6 months an attempt was made to discontinue the MAOI and continue only with amitryptiline. At the end of the study, 4 patients maintained response with single medication, 6 still required both drugs and 2 relapsed. No clinical differences were apparent between the outcome groups, except that those who maintained their response only with the 2 combined drugs had more previous depressive episodes than the others. The isocarboxazide/amitryptiline combination may be a good treatment option for at least some forms of resistant depression. The safety of this treatment modality is confirmed, even when given for long periods of time. The study also suggest that there are no clinical characteristics in resistant depression that may predict the treatment outcome but, perhaps in some patients, a combined treatment is required to obtain a broader biochemical effect that could convert them from nonresponders to responders.

MAOIs in the contemporary treatment of depression.

We review the literature on the effectiveness of the monoamine oxidase inhibitors (MAOIs) and present metaanalyses of controlled trials comparing the FDA-approved MAOIs with both placebo and comparator tricyclic antidepressants. For outpatients, metaanalyses with intent-to-treat samples revealed generally comparable overall efficacy for phenelzine, isocarboxazid, and tranylcypromine. Drug-placebo differences were 29.5% (+/- 11.1%) (phenelzine; nine studies), 41.3% (+/- 18.0%) (isocarboxazid; three studies), and 22.1% (+/- 25.4%) (tranylcypromine; three studies). For inpatients, phenelzine was 22.3% (+/- 30.7%) (five studies) more effective than placebo, whereas the isocarboxazid-placebo difference was lower (15.3%) (+/- 12.6%). Both phenelzine and isocarboxazid were significantly less effective than comparator tricyclics for inpatients, whereas tranylcypromine has not been adequately studied. Both phenelzine and tranylcypromine appear to be more effective than tricyclics in depressed outpatients with atypical features. Monoamine oxidase inhibitors are also effective treatments for outpatients who have failed to respond to tricyclic antidepressants. Our review also suggests (1) the FDA-approved MAOIs treat a somewhat different group of patients than tricyclics; (2) more severely depressed inpatients may not respond as well to MAOIs as to tricyclics; and (3) because of preferential MAOI responsivity, atypical or anergic depressions may be biologically different than classical depressions.

Serotonin syndrome.

We describe a patient treated with trazodone, isocarboxazid, and methylphenidate hydrochloride who developed confusion, agitation, poor concentration, rigidity, myoclonus, involuntary movements, orthostatic hypotension, and hyperreflexia. CK was normal, and the syndrome resolved spontaneously over 12 hours. The serotonin syndrome occurs following the use of serotomimetic agents (serotonin reuptake inhibitors, tricyclic and tetracyclic antidepressants, tryptophan, 3,4-methylenedioxy-methamphetamine, dextromethorphan, meperidine, S-adenosylmethionine) alone or in combination with monoamine oxidase inhibitors. It is characterized by various combinations of myoclonus, rigidity, hyperreflexia, shivering, confusion, agitation, restlessness, coma, autonomic instability, low-grade fever, nausea, diarrhea, diaphoresis, flushing, and rarely, rhabdomyolysis and death.

The effects of phenelzine and other monoamine oxidase inhibitor antidepressants on brain and liver I2 imidazoline-preferring receptors.

1. The binding of [3H]-idazoxan in the presence of 10(-6) M (-)-adrenaline was used to quantitate I2 imidazoline-preferring receptors in the rat brain and liver after chronic treatment with various irreversible and reversible monoamine oxidase (MAO) inhibitors. 2. Chronic treatment (7-14 days) with the irreversible MAO inhibitors, phenelzine (1-20 mg kg-1, i.p.), isocarboxazid (10 mg kg-1, i.p.), clorgyline (3 mg kg-1, i.p.) and tranylcypromine (10 mg kg-1, i.p.) markedly decreased (21-71%) the density of I2 imidazoline-preferring receptors in the rat brain and liver. In contrast, chronic treatment (7 days) with the reversible MAO-A inhibitors, moclobemide (1 and 10 mg kg-1, i.p.) or chlordimeform (10 mg kg-1, i.p.) or with the reversible MAO-B inhibitor Ro 16-6491 (1 and 10 mg kg-1, i.p.) did not alter the density of I2 imidazoline-preferring receptors in the rat brain and liver; except for the higher dose of Ro 16-6491 which only decreased the density of these putative receptors in the liver (38%). 3. In vitro, phenelzine, clorgyline, 3-phenylpropargylamine, tranylcypromine and chlordimeform displaced the binding of [3H]-idazoxan to brain and liver I2 imidazoline-preferring receptors from two distinct binding sites. Phenelzine, 3-phenylpropargylamine and tranylcypromine displayed moderate affinity (KiH = 0.3-6 microM) for brain and liver I2 imidazoline-preferring receptors; whereas chlordimeform displayed high affinity (KiH = 6 nM) for these receptors in the two tissues studied, Clorgyline displayed very high affinity for rat brain (KiH = 40 pM) but not for rat liver I2 imidazoline-preferring receptors (KiH = 169 nM). 4. Preincubation of cortical or liver membranes with phenelzine (10-4 M for 30 min) did not alter the total density of I2 imidazoline-preferring receptors, indicating that this irreversible MAO inhibitor does not irreversibly bind to I2 imidazoline-preferring receptors. In contrast, preincubation with 10-6 Mclorgyline reduced by 40% the Bmax of [3H]-idazoxan to brain and liver I2 imidazoline-preferring receptors.5. Chronic treatment (7 days) with the inducers of cytochrome P-450 enzymes phenobarbitone (40 or 80 mg kg-1, i.p.), 3-methylcholanthrene (20 mg kg-1, i.p.) or 2-methylimidazole (40 mg kg-1, i.p.) did not alter the binding parameters of [3H]-idazoxan to brain and liver 12 imidazoline-preferring receptors.The compound SKF 525A, a potent inhibitor of cytochrome P-450 enzymes which forms a tight but reversible complex with the haemoprotein, completely displaced with moderate affinity (KiH = 2-10 microM)the specific binding of [3H]-idazoxan to brain and liver 12 imidazoline-preferring receptors. Preincubation of total liver homogenates with 3 x 10-4 M phenelzine in the presence of 10-3 M NADH, a treatment that irreversibly inactivates the haeme group of cytochrome P-450, did not reduce the density of liver I2 imidazoline-preferring receptors. These results discounted a possible interaction of [3H]-idazoxan with the haeme group of cytochrome P-450 enzymes.6. Together the results indicate that the down-regulation of I2 imidazoline-preferring receptors is associated with an irreversible inactivation of MAO (at least in the brain) that is not related either to the affinity of the MAO inhibitors for I2 imidazoline-preferring receptors or to an irreversible binding to these putative receptors. These findings indicate a novel effect of irreversible MAO inhibitors in the brain and suggest a new target for these compounds that could be of relevance in the treatment of depression, a disease in which an increased density of brain I2 imidazoline-preferring receptors has been reported.