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Isocarboxazid Side Effects

For the Consumer

Applies to isocarboxazid: oral tablet

Along with its needed effects, isocarboxazid may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking isocarboxazid:

Less common
  • Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • chills
  • cold sweats
  • confusion
  • difficult urination
  • dizziness, faintness, or lightheadedness when getting up from lying or sitting position
  • fainting
  • fast, irregular, pounding, or racing heartbeat or pulse
  • fear or nervousness
  • heavy feeling
  • increased need to urinate
  • passing urine more often
  • restlessness
  • shakiness in the legs, arms, hands, or feet
  • sudden jerky movements of the body
  • sweating
  • trembling or shaking of the hands or feet
  • trouble sitting still
Incidence not known
  • Agitation
  • burning while urinating
  • change in consciousness
  • decrease in frequency of urination
  • decrease in urine volume
  • decreased urine output
  • depression
  • difficulty in passing urine (dribbling)
  • dizziness
  • false or unusual sense of well-being
  • headache
  • hostility
  • irritability
  • loss of bladder control
  • loss of consciousness
  • muscle twitching
  • nausea
  • need to keep moving
  • numbness or tingling of the hands, feet, or face
  • rapid weight gain
  • seeing, hearing, or feeling things that are not there
  • seizures
  • shakiness and unsteady walk
  • stupor
  • swelling of the face, ankles, or hands
  • unsteadiness, trembling, or other problems with muscle control or coordination
  • unusual tiredness or weakness

Some side effects of isocarboxazid may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
  • Constipation
  • dry mouth
Less common
  • Decreased interest in sexual intercourse
  • drowsiness
  • inability to have or keep an erection
  • loss in sexual ability, desire, drive, or performance
  • relaxed and calm
  • sleepiness
  • sleeplessness
  • trouble sleeping
  • unable to sleep
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
Incidence not known
  • Black tongue
  • blurred vision
  • change in vision
  • impaired vision
  • increased sensitivity of the skin to sunlight
  • itching
  • raised, dark red, wart-like spots on the skin, especially when used on the face
  • redness or other discoloration of the skin
  • severe sunburn
  • skin rash

For Healthcare Professionals

Applies to isocarboxazid: oral tablet


Common (1% to 10%): Orthostatic hypotension, palpitations
Frequency not reported: Disturbances in cardiac rhythm[Ref]

Hypertensive crisis can occur during isocarboxazid therapy and is characterized by some or all of the following symptoms: occipital headache that may radiate frontally, palpitation, neck stiffness or soreness, nausea or vomiting, sweating that is sometimes accompanied by fever or cold, clammy skin, pupil dilatation, photophobia, tachycardia or bradycardia, and constricting chest pain. Intracranial bleeding, which can be fatal, has also been reported with the paradoxical increase in blood pressure. Hypertensive crises may be precipitated by concomitant administration of sympathomimetic drugs or related compounds or other MAO inhibitors. Ingestion of foods with a high concentration of tyramine or dopamine and excessive amounts of caffeine and chocolate may also cause a hypertensive crisis. Blood pressure should be monitored frequently in all patients and therapy discontinued immediately upon the occurrence of palpitation or frequent headaches, as these signs may be prodromal of a hypertensive crisis.[Ref]

Nervous system

Very common (10% or more): Dizziness (29%), headache (15%)
Common (1% to 10%): Drowsy, tremor, myoclonic jerks, paresthesia, forgetful, hyperactive, lethargy, sedation, syncope
Frequency not reported: Hyperreflexia, overactivity
Postmarketing reports: Akathisia, ataxia, coma, neuritis[Ref]


Common (1% to 10%): Dry mouth, constipation, nausea, diarrhea
Frequency not reported: Vomiting
Postmarketing reports: Black tongue[Ref]


Frequency not reported: Blurred vision
Postmarketing reports: Toxic amblyopia[Ref]


Common (1% to 10%): Chills, heavy feeling
Frequency not reported: Muscle tremor[Ref]


Common (1% to 10%): Urinary hesitancy, urinary frequency, impotence
Frequency not reported: Impairment of erection and ejaculation
Postmarketing reports: Dysuria, incontinence, urinary retention[Ref]


The most common adverse events were dizziness, headache, nausea, and dry mouth.[Ref]


Postmarketing reports: Impaired water secretion compatible with syndrome of inappropriate secretion of antidiuretic hormone (SIADH)[Ref]


Common (1% to 10%): Sweating
Frequency not reported: Skin rashes
Postmarketing reports: Photosensitivity, spider telangiectases[Ref]


Frequency not reported: Difficulty in micturition[Ref]


Hallucinations have been reported with high doses, but have disappeared with dose reduction or discontinuation of therapy.[Ref]

Common (1% to 10%): Insomnia, sleep disturbance, anxiety
Frequency not reported: Confusion, behavioral changes, suicidal ideation, suicidal behavior
Postmarketing reports: Hallucinations[Ref]


Frequency not reported: Peripheral edema, fatigue, weakness[Ref]


Rare (less than 0.1%): Blood dyscrasias (purpura, granulocytopenia)
Postmarketing reports: Hematologic changes[Ref]


1. "Product Information. Marplan (isocarboxazid)" Roche Laboratories, Nutley, NJ.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Some side effects of isocarboxazid may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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