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Phenelzine Side Effects

For the Consumer

Applies to phenelzine: oral tablet

Oral route(Tablet)

Antidepressants increased the risk of suicidal thinking and behavior in children, adolescents, and young adults in short-term studies with major depressive disorder (MDD) and other psychiatric disorders. Short term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24, and there was a reduction in risk with antidepressants compared to placebo in adults aged 65 and older. This risk must be balanced with the clinical need. Monitor patients closely for clinical worsening, suicidality, or unusual changes in behavior. Families and caregivers should be advised of the need for close observation and communication with the prescriber. Not approved for use in pediatric patients .

Along with its needed effects, phenelzine 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 phenelzine:

More Common

  • Chills
  • cold sweats
  • confusion
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position
  • overactive reflexes
  • shakiness in the legs, arms, hands, or feet
  • sudden jerky movements of the body
  • swelling
  • trembling or shaking of the hands or feet

Less Common

  • Abdominal or stomach pain
  • actions that are out of control
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • change in consciousness
  • clay-colored stools
  • dark urine
  • decrease in frequency of urination
  • decrease in urine volume
  • difficult or troubled breathing
  • difficulty in passing urine (dribbling)
  • disorganized thoughts
  • dizziness
  • drowsiness
  • false or unusual sense of well-being
  • fast, pounding, or irregular heartbeat or pulse
  • fear or nervousness
  • fever
  • general feeling of discomfort, illness, or weakness
  • headache
  • high blood pressure
  • increased sweating
  • irregular, fast or slow, or shallow breathing
  • irritability
  • itching
  • lack of emotion or feelings
  • loss of appetite
  • loss of consciousness
  • loud or fast speech
  • low blood pressure
  • muscle tremors
  • muscle twitching
  • nausea or vomiting
  • nervousness
  • no emotion or expression in speech
  • painful urination
  • pale or blue lips, fingernails, or skin
  • rapid, deep, or shallow breathing
  • rash
  • restlessness
  • seeing or hearing things that are not there
  • seizures
  • shakiness and unsteady walk
  • shortness of breath
  • slow or irregular heartbeat
  • stomach cramps
  • sweating
  • swelling of the feet or lower legs
  • talking, feeling, and acting with excitement
  • uncontrolled eye movements
  • unpleasant breath odor
  • unsteadiness, trembling, or other problems with muscle control or coordination
  • unusual paleness
  • unusual tiredness or weakness
  • vomiting of blood
  • weakness
  • yellow eyes or skin

Some side effects of phenelzine 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
  • decreased interest in sexual intercourse
  • diarrhea
  • dry mouth
  • inability to have or keep an erection
  • indigestion
  • loss in sexual ability, desire, drive, or performance
  • loss of appetite
  • not able to have an orgasm
  • passing of gas
  • sleeplessness
  • stomach pain, fullness, or discomfort
  • trouble sleeping
  • unable to sleep
  • unusually deep sleep
  • unusually long duration of sleep
  • weight gain

Less Common

  • Blindness
  • blurred vision
  • decreased vision
  • eye pain
  • redness, swelling, or soreness of the tongue
  • tearing

For Healthcare Professionals

Applies to phenelzine: oral tablet


The most important adverse event reported is hypertensive crisis, which has been associated with intracranial bleeding and has been fatal.[Ref]


Common (1% to 10%): Postural hypotension

Uncommon (0.1% to 1%): Arrhythmias

Frequency not reported: Hypertensive crisis[Ref]


Common (1% to 10%): Gastrointestinal disturbances (nausea, vomiting, dryness of mouth, constipation)[Ref]


Common (1% to 10%): Weakness, fatigue, adverse effects on driving ability, tremors

Uncommon (0.1% to 1%): Jitteriness

Very rare (less than 0.01%): Transient respiratory and cardiovascular depression following ECT, fever associated with increased muscle tone

Frequency not reported: Withdrawal, withdrawal syndrome[Ref]

-Withdrawal may be associated with nausea, vomiting, and malaise.

-An uncommon withdrawal syndrome following abrupt drug discontinuation generally starts after 24 to 72 hours and may vary from vivid nightmares and agitation to frank psychosis and convulsions.

-Withdrawal syndrome generally responds to reinstitution of low dose therapy, followed by cautious downward titration and discontinuation.[Ref]

Nervous system

Common (1% to 10%): Dizziness, headache, drowsiness, sleep disturbances (including insomnia and hypersomnia), myoclonic movements, hyperreflexia

Uncommon (0.1% to 1%): Paresthesia, peripheral neuritis, convulsions, palilalia, nystagmus

Very rare (less than 0.01%): Ataxia, shock-like coma, neuroleptic malignant syndrome (occasionally fatal)[Ref]


Common (1% to 10%): Insomnia, anorgasmia

Uncommon (0.1% to 1%): Nervousness, euphoria, behavioral changes, confusion, hallucinations

Very rare (less than 0.01%): Toxic delirium, manic reaction, acute anxiety reaction, precipitation of schizophrenia

Frequency not reported: Suicidal ideation, suicidal behaviors[Ref]


Common (1% to 10%): Sexual disturbances (anorgasmia and ejaculatory disturbances)

Uncommon (0.1% to 1%): Difficulty in micturition, impotence and delayed ejaculation[Ref]


Uncommon (0.1% to 1%): Blood dyscrasias

Frequency not reported: Leukopenia[Ref]


Common (1% to 10%): Elevated serum transaminases

Uncommon (0.1% to 1%): Elevated liver enzymes

Very rare (less than 0.01%): Fatal progressive necrotizing hepatocellular damage, reversible jaundice[Ref]


Common (1% to 10%): Edema, weight gain

Uncommon (0.1% to 1%): Increased appetite, hypernatremia

Very rare (less than 0.01%): Hypermetabolic syndrome

Frequency not reported: Hyponatremia, inappropriate ADH secretion[Ref]


Common (1% to 10%): Twitching

Uncommon (0.1% to 1%): Muscle tremor[Ref]


Common (1% to 10%): Blurred vision

Uncommon (0.1% to 1%): Glaucoma[Ref]


Uncommon (0.1% to 1%): Sweating, rash, pruritus, purpura[Ref]


Very rare (less than 0.01%): Edema of the glottis[Ref]


Frequency not reported: Lupus-like illness[Ref]


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

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. "Product Information. Nardil (phenelzine)." Parke-Dvis, Morris Plains, NJ.

Further information

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

Some side effects may not be reported. You may report them to the FDA.