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Isocarboxazid Dosage

Medically reviewed by Last updated on Nov 8, 2021.

Applies to the following strengths: 10 mg

Usual Adult Dose for Depression

Initial dose: 10 mg orally 2 times a day

  • Increase in 10 mg increments every 2 to 4 days, until 40 mg/day is reached (by the end of the first week of treatment); doses should be divided into 2 to 4 doses per day.
  • After the first week, the dose may be increased in increments of up to 20 mg per week, if needed and tolerated.
Maximum dose: 60 mg/day

  • Doses should be adjusted based on careful observation of the patient.
  • After the maximum clinical response is achieved, prescribers should consider reducing the dose slowly over several weeks without jeopardizing therapeutic response.
  • Benefits may not be seen for 3 to 6 weeks; if a response does not occur within this time, continued use is unlikely to help.
  • Efficacy has not been established in studies lasting longer than 6 weeks; patients requiring treatment longer than 6 weeks should be evaluated for usefulness.
  • Use with caution if doses above 40 mg/day are used.

Use: Second-line treatment of depression, especially major depressive disorder in patients with or without signs/symptoms of anxiety (e.g., anxious mood, panic, phobic symptoms) who have not responded satisfactorily to other antidepressants

Renal Dose Adjustments

Mild to moderate renal dysfunction: Use with caution.
Severe renal dysfunction: Contraindicated

Liver Dose Adjustments

History of liver disease or with abnormal liver function tests: Contraindicated

First sign/symptom of liver dysfunction or jaundice: Discontinue use.

Dose Adjustments

Switching FROM:

  • Fluoxetine: Allow at least 5 weeks after stopping fluoxetine and starting this drug.
  • Sertraline or paroxetine: Allow at least 2 weeks after stopping sertraline or paroxetine and starting this drug.

Switching TO/FROM this drug from another MAOI or from a dibenzazepine-related entity:
  • Allow a medication-free interval of at least 1 week.
  • Initiate this drug at half the normal starting dose for at least the first week of therapy.

Switching TO:
  • Bupropion: Allow at least 14 days after stopping this drug.
  • Buspirone: Allow at least 10 days after stopping this drug.
  • Meperidine: Allow at least 2 to 3 weeks after stopping this drug.
  • Selective serotonin reuptake inhibitors (SSRIs), including fluoxetine: Allow at least 10 to 14 days after stopping this drug.



  • Antidepressants increased the risk compared to placebo of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults in short-term studies with major depressive disorder (MDD) and other psychiatric disorders.
  • Anyone considering the use of this drug or any other antidepressant in a child, adolescent or young adult must balance this risk with the clinical need. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond 24 age 24; there was a reduction in risk with antidepressants compared to placebo in adults aged 65 and older.
  • Depression and certain other psychiatric disorders are themselves associated with increases in the risk of suicide.
  • Patients of all ages who are started on antidepressant therapy should be monitored appropriately and observed closely for clinical worsening, suicidality, or unusual changes in behavior.
  • Families and caregivers should be apprised of the need for close observation and communication with the prescriber.
  • This drug is not approved for use in pediatric patients.
  • Pooled analyses of short-term (4 to 16 weeks) placebo-controlled trials of 9 antidepressant drugs (SSRIs and others) in children and adolescents with MDD, obsessive compulsive disorder (OCD), or other psychiatric disorders (a total of 24 trials involving over 4400 patients) have revealed a greater risk of adverse events representing suicidal thinking or behavior (suicidality) during the first few months of treatment in those receiving antidepressants. The average risk of such events in patients receiving antidepressants was 4%, twice the placebo risk of 2%. No suicides occurred in these trials.

Safety and efficacy have not been established in patients younger than 16 years; this drug is not recommended for use in these patients.

Consult WARNINGS section for additional precautions.


Data not available.

Other Comments

Storage requirements:

  • Store below 25C.

  • Limitation of use: This drug is not recommended as a first-line treatment for patients who are newly diagnosed with depression.
  • Treatment has not been adequately studied in patients with endogenomorphical retardation, delusional depression, or in hospitalized depressed patients.

  • Cardiovascular: Blood pressure, heart rate, signs/symptoms of hypertensive crisis and palpitations
  • Hepatic: Liver function tests
  • Nervous system: Headaches (change or presence)
  • Psychiatric: Emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.

Patient advice:
  • Advise patients to avoid the following foods and medications during phenelzine therapy and for two weeks after discontinuing use: pickled herring, liver, dry sausage, broad bean pods, sauerkraut, aged cheese, yogurt, beer and wine, alcohol-free and reduced-alcohol beer and wine products, yeast extract, meat extract, excessive amounts of chocolate and caffeine, cough and cold preparations, nasal decongestants (tablets, drops, or sprays), asthma inhalant medications, weight-loss agents, and L-tryptophan containing preparations.
  • Promptly report headache or other unusual symptoms (i.e. palpitation or tachycardia, sense of constriction in the throat or chest, sweating, dizziness, neck stiffness, nausea, or vomiting).
  • Do not eat foods listed under contraindications and do not drink alcoholic beverages.
  • There is a possibility of hypotension and faintness, as well as drowsiness that may impair performance of hazardous tasks, such as driving or operating machinery.
  • Do not consume excessive caffeine in any form.
  • Inform physicians and dentists about your use of this drug.

Frequently asked questions

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.