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Periactin Side Effects

Generic name: cyproheptadine

Medically reviewed by Last updated on Jan 22, 2024.

Note: This document contains side effect information about cyproheptadine. Some dosage forms listed on this page may not apply to the brand name Periactin.

Applies to cyproheptadine: oral solution, oral tablets.

Side effects include:

Sedation, sleepiness (often transient), dizziness, disturbed coordination, restlessness, excitation.

For Healthcare Professionals

Applies to cyproheptadine: compounding powder, oral syrup, oral tablet.


The most commonly reported side effects included drowsiness and somnolence.[Ref]

Nervous system

Common (1% to 10%): Drowsiness, somnolence

Frequency not reported: Convulsions, coordination disturbance, dizziness, faintness, headache, neuritis, paresthesias, sedation/transient sedation, sleepiness/transient sleepiness, tremor, vertigo[Ref]

Some patients who developed drowsiness initially had an apparent improvement in symptoms when they continued taking this drug continuously over the next 3 to 4 days.[Ref]


Frequency not reported: Aggressive behavior, confusion, euphoria, excitation, hallucinations, hysteria, insomnia, irritability, nervousness, restlessness[Ref]


Frequency not reported: Constipation, diarrhea, dry mouth, epigastric distress, nausea, vomiting[Ref]


Frequency not reported: Difficult urination/micturition difficulty, early menses, micturition frequency/urinary frequency, urinary retention[Ref]


Frequency not reported: Chest tightness, dry nose, dry throat, nasal stuffiness, thickened bronchial secretions, wheezing[Ref]


Frequency not reported: Cholestasis, hepatitis, jaundice, liver failure, liver function abnormality[Ref]


Frequency not reported: Allergic rash, excessive perspiration, photosensitivity, urticaria[Ref]


Frequency not reported: Extrasystoles, hypotension, palpitation, tachycardia[Ref]


Frequency not reported: Agranulocytosis, hemolytic anemia, leukopenia, thrombocytopenia[Ref]


Frequency not reported: Anorexia, increased appetite, weight gain[Ref]


Frequency not reported: Chills, fatigue, rigors[Ref]


Frequency not reported: Allergic edema, anaphylactic shock[Ref]


Frequency not reported: Blurred vision, diplopia[Ref]


Frequency not reported: Acute labyrinthitis[Ref]


1. Product Information. Periactin (cyproheptadine). Merck & Co., Inc. 2002;PROD.

2. Cerner Multum, Inc. UK Summary of Product Characteristics.

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.