Phenelzine Side Effects

Medically reviewed by Drugs.com. Last updated on Jul 17, 2023.

Applies to phenelzine: oral tablet.

Serious side effects of Phenelzine

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

Other side effects of Phenelzine

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.

General

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

Nervous system

Common (1% to 10%): Dizziness, drowsiness, headache, hyperreflexia, myoclonic movements, tremors

Uncommon (0.1% to 1%): Convulsions, palilalia, paresthesia, peripheral neuritis

Rare (0.01% to 0.1%): Acute dystonic reaction, ataxia, coma, neuroleptic malignant syndrome (occasionally fatal), sensorimotor peripheral neuropathy, shock-like coma, speech blockade, transient respiratory and cardiovascular depression following ECT

Frequency not reported: Intracranial bleeding/fatal intracranial bleeding, occipital headache/occipital headache which may radiate frontally^[Ref]

Psychiatric

Common (1% to 10%): Anorgasmia, hypersomnia, hypomania, insomnia, sleep disturbances

Uncommon (0.1% to 1%): Agitation, behavioral changes, confusion, euphoria, frank psychosis, hallucinations, nervousness, vivid nightmares

Rare (0.01% to 0.1%): Acute anxiety reaction, delusional parasitosis, manic reaction, precipitation of schizophrenia, toxic delirium

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

Gastrointestinal

Common (1% to 10%): Constipation, dry mouth, gastrointestinal disturbances, nausea, vomiting^[Ref]

Genitourinary

Common (1% to 10%): Anorgasmia, ejaculatory disturbances, impotence, sexual disturbances

Uncommon (0.1% to 1%): Delayed ejaculation, difficulty in micturition, urinary retention^[Ref]

Other

Common (1% to 10%): Adverse effects on driving ability, fatigue, weakness

Uncommon (0.1% to 1%): Jitteriness, withdrawal/withdrawal syndrome

Rare (less than 0.1%): Fever associated with increased muscle tone, hyperpyrexia, malaise^[Ref]

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

Withdrawal syndrome occurred after abrupt drug discontinuation, and generally started after 24 to 72 hours; signs/symptoms varied from vivid nightmares and agitation to frank psychosis and convulsions. The withdrawal syndrome generally responded to reinstitution of low dose therapy, followed by cautious downward titration and discontinuation.^[Ref]

Cardiovascular

Common (1% to 10%): Edema, postural hypotension

Uncommon (0.1% to 1%): Arrhythmias

Rare (0.01% to 0.1%): Blood pressure changes, tachycardia

Frequency not reported: Bradycardia, constricting chest pain, hypertensive crisis, palpitation^[Ref]

Metabolic

Common (1% to 10%): Weight gain

Uncommon (0.1% to 1%): Hypernatremia, increased appetite

Rare (0.01% to 0.1%): Hypermetabolic syndrome, metabolic acidosis

Frequency not reported: Hyponatremia^[Ref]

Hyponatremia may be more likely to occur in older patients or in those with inappropriate secretion of antidiuretic hormone; this side effect should be considered in patients treated with antidepressants who present with confusion, convulsions, and/or drowsiness.

Hypermetabolic syndrome may resemble signs/symptoms of an overdose.^[Ref]

Ocular

Common (1% to 10%): Blurred vision

Uncommon (0.1% to 1%): Glaucoma, nystagmus

Frequency not reported: Dilated pupils, photophobia^[Ref]

Musculoskeletal

Common (1% to 10%): Twitching

Uncommon (0.1% to 1%): Muscle tremor

Rare (0.01% to 0.1%): Elevated creatine kinase levels, muscular rigidity

Frequency not reported: Neck soreness, neck stiffness^[Ref]

Hepatic

Common (1% to 10%): Elevated serum transaminases (without accompanying signs/symptoms)

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

Rare (less than 0.1%): Fatal progressive necrotizing hepatocellular damage, reversible jaundice^[Ref]

Dermatologic

Uncommon (0.1% to 1%): Pruritus, purpura, rash/skin rash, sweating

Frequency not reported: Sweating with cold, clammy skin or fever^[Ref]

Hematologic

Uncommon (0.1% to 1%): Blood dyscrasias

Rare (less than 0.1%): Leucopenia^[Ref]

Immunologic

Uncommon (0.1% to 1%): Lupus-like illness^[Ref]

Respiratory

Rare (0.01% to 0.1%): Hypoxia, tachypnea^[Ref]

Hypersensitivity

Rare (0.01% to 0.1%): Edema of the glottis^[Ref]

Endocrine

Rare (0.01% to 0.1%): Inappropriate secretion of antidiuretic hormone/ADH secretion^[Ref]

Frequently asked questions

• What are some common side effects of antidepressants?

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.

Medical Disclaimer