Isocarboxazid
Isocarboxazid is a monoamine oxidase inhibitor (MAOI) indicated for the treatment of depression in patients who have not responded to other antidepressant therapies. As an irreversible, non-selective MAOI, it is typically reserved for treatment-resistant depression due to significant dietary restrictions and drug interactions.
Clinical Overview
Primary Clinical Applications
Isocarboxazid is indicated for depression that has not responded to other antidepressant classes. It may be particularly effective for atypical depression characterized by mood reactivity, hypersomnia, hyperphagia, and rejection sensitivity. MAOIs are considered when other treatments have failed.
Mechanism and Clinical Considerations
Isocarboxazid irreversibly inhibits both MAO-A and MAO-B enzymes, increasing levels of norepinephrine, serotonin, and dopamine. This broad mechanism may explain its efficacy in treatment-resistant cases but also accounts for its extensive interactions and dietary restrictions.
Safety and Monitoring Requirements
Treatment with isocarboxazid requires strict adherence to tyramine-restricted diet and careful monitoring for hypertensive crises. Patients must avoid numerous medications and foods high in tyramine. The irreversible nature of MAO inhibition means effects persist for weeks after discontinuation.
Key Clinical Points
Tyramine-restricted diet is mandatory
Aged cheeses, cured meats, fermented foods, and alcohol can precipitate hypertensive crisis. Dietary counselling is a prerequisite for prescribing, not an afterthought, and needs to be revisited at follow-up.
Irreversible inhibition outlasts the last dose
MAO inhibition persists for weeks after stopping because new enzyme must be synthesised. Dietary and drug restrictions therefore continue well beyond discontinuation.
Fourteen-day gap in both directions
Fourteen days must separate isocarboxazid from any other antidepressant. Meperidine and dextromethorphan are contraindicated outright, and elective surgery requires discontinuation ten days beforehand.
Particular value in atypical depression
MAOIs remain notably effective where depression features mood reactivity, hypersomnia, hyperphagia, and rejection sensitivity, which is the clinical niche justifying the burden of restrictions.
Broad cardiovascular contraindications
Contraindicated in cardiovascular and cerebrovascular disease, phaeochromocytoma, severe renal or hepatic impairment, and a history of headache. Orthostatic hypotension is the most common day-to-day adverse effect.
Prescribing Information
Dosing & Administration
Depression – Adults:
- Initial: 10 mg twice daily
- Titration: May increase by 10 mg every 2-4 days
- Effective dose: Usually 20-30 mg daily in divided doses
- Maximum: 60 mg daily (doses >40 mg/day require caution)
Elderly:
- Initial: 5-10 mg daily
- Titrate slowly with careful monitoring
Administration:
- Take with food to reduce GI upset
- Divide daily dose into 2-4 administrations
Indications
- Depression in patients who have not responded to other antidepressant therapy
- Typically reserved for treatment-resistant depression
Contraindications
- Hypersensitivity to isocarboxazid
- Concomitant use with other MAOIs, SSRIs, SNRIs, tricyclics
- Use with sympathomimetics, meperidine, dextromethorphan
- Pheochromocytoma
- Cardiovascular disease, cerebrovascular disease
- Severe renal or hepatic impairment
- History of headache or liver disease
Warnings & Precautions
- Boxed Warning: Increased risk of suicidal thoughts and behavior in patients under 25 years
- Hypertensive crisis: Risk with tyramine-containing foods and certain drugs
- Dietary restrictions: Avoid aged cheeses, cured meats, fermented foods, alcohol
- Drug interactions: Extensive list of contraindicated medications
- Withdrawal: Taper gradually to avoid discontinuation syndrome
Drug Interactions
- Antidepressants: Wait 14 days between MAOI and other antidepressants
- Sympathomimetics: Risk of hypertensive crisis
- Meperidine: Contraindicated – risk of serotonin syndrome
- Tyramine-rich foods: Hypertensive crisis risk
- Anesthetics: Discontinue 10 days before elective surgery
Adverse Reactions
Common:
- Orthostatic hypotension, dizziness, headache, drowsiness
- Dry mouth, constipation, nausea
Serious:
- Hypertensive crisis, hepatotoxicity, serotonin syndrome
Special Populations
- Elderly: Increased risk of orthostatic hypotension, start with lower doses
- Hepatic/Renal Impairment: Contraindicated in severe impairment
- Pregnancy: Category C – use only if clearly needed
- Dietary Education: Essential patient counseling on tyramine restrictions
Frequently Asked Questions
What is Isocarboxazid used for?
Isocarboxazid is a monoamine oxidase inhibitor (MAOI) indicated for the treatment of depression in patients who have not responded to other antidepressant therapies. As an irreversible, non-selective MAOI, it is typically reserved for treatment-resistant depression due to significant dietary restrictions and drug interactions.
What class of drug is Isocarboxazid?
Isocarboxazid is classified as: Monoamine Oxidase Inhibitor (MAOI).
Tyramine-restricted diet is mandatory?
Aged cheeses, cured meats, fermented foods, and alcohol can precipitate hypertensive crisis. Dietary counselling is a prerequisite for prescribing, not an afterthought, and needs to be revisited at follow-up.
Irreversible inhibition outlasts the last dose?
MAO inhibition persists for weeks after stopping because new enzyme must be synthesised. Dietary and drug restrictions therefore continue well beyond discontinuation.
Fourteen-day gap in both directions?
Fourteen days must separate isocarboxazid from any other antidepressant. Meperidine and dextromethorphan are contraindicated outright, and elective surgery requires discontinuation ten days beforehand.
Particular value in atypical depression?
MAOIs remain notably effective where depression features mood reactivity, hypersomnia, hyperphagia, and rejection sensitivity, which is the clinical niche justifying the burden of restrictions.
Source: FDA prescribing information (DailyMed)