1. Clinical Overview
Cyproheptadine is a first-generation piperidine antihistamine with potent serotonin (5-HT2) and histamine (H1) receptor antagonist activity. It is widely used in India for its appetite-stimulating effects, management of allergic conditions, and as an adjunct in migraine prophylaxis. Its anticholinergic and sedative properties are significant.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 15-30 minutes for antihistaminic effects; Appetite stimulation may take 1-2 weeks of regular dosing. | Approximately 4-6 hours for antihistaminic effects; Appetite effects are sustained with chronic use. | Well absorbed from the GI tract, but undergoes significant first-pass metabolism. Absolute bioavailability is not precisely established but is estimated to be moderate. |
2. Mechanism of Action
Cyproheptadine competitively and reversibly blocks histamine at H1 receptor sites on effector cells, preventing histamine-mediated allergic symptoms. It also acts as a potent antagonist at serotonin (5-HT2) receptors. The appetite-stimulating effect is attributed to a combination of antiserotonergic activity (serotonin is an appetite suppressant) and antihistaminic effect (histamine H1 antagonism in the hypothalamus may stimulate appetite). Its anticholinergic action contributes to side effects like dry mouth.
3. Indications & Uses
- Allergic conditions: Allergic rhinitis, Conjunctivitis, Urticaria, Angioedema
- Appetite stimulation in underweight individuals, failure to thrive, and anorexia
- Pruritus of allergic or non-allergic origin
4. Dosage & Administration
Adult Dosage: Allergy/Pruritus: 4 mg orally three times daily. Initial dose may be 2-4 mg at bedtime. Max: 0.5 mg/kg/day. Appetite Stimulation: 2-4 mg three times daily, 30 minutes before meals. Migraine Prophylaxis: 4 mg 2-4 times daily.
Administration: Administer with or without food. For appetite stimulation, take 30 minutes before meals. Tablet can be crushed if needed. Avoid alcohol and CNS depressants. Maintain adequate hydration.
5. Side Effects
Common side effects may include:
- Drowsiness, sedation, somnolence
- Dry mouth, nose, and throat
- Dizziness
- Increased appetite and weight gain
- Thickened bronchial secretions
- Constipation
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Alcohol, Benzodiazepines, Opioids, other CNS Depressants | Additive CNS depression, profound sedation, impaired psychomotor performance. | Major |
| Monoamine Oxidase Inhibitors (MAOIs) e.g., Phenelzine, Selegiline | Potentiates anticholinergic and CNS depressant effects; hypertensive crisis risk. | Contraindicated |
| Anticholinergic drugs (e.g., Atropine, Tricyclic Antidepressants, Antipsychotics) | Additive anticholinergic effects (dry mouth, constipation, urinary retention, confusion). | Major |
| SSRIs/SNRIs (e.g., Fluoxetine, Sertraline, Venlafaxine) | Theoretical reduction in efficacy of cyproheptadine's antiserotonergic action; used cautiously in serotonin syndrome. | Moderate |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Erythromycin, Clarithromycin) | Increased cyproheptadine plasma levels, risk of toxicity. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | Decreased cyproheptadine plasma levels, reduced efficacy. | Moderate |
7. Patient Counselling
- DO take as prescribed, usually before meals for appetite effect.
- DO report excessive drowsiness, confusion, or palpitations.
- DO maintain good oral hygiene to manage dry mouth.
- DO use sugar-free gum or candies for dry mouth relief.
- DONT drive or operate heavy machinery until you know how the medicine affects you.
- DONT consume alcohol or sleep-inducing medications.
- DONT take with MAO inhibitors.
- DONT stop taking suddenly if used for migraine prophylaxis; consult doctor.
8. Toxicology & Storage
Overdose: Symptoms are primarily CNS depression (somnolence, coma, respiratory depression, cardiovascular collapse) or CNS stimulation (hallucinations, tremors, convulsions) especially in children. Anticholinergic crisis: fixed dilated pupils, flushing, hyperthermia, dry mouth, urinary retention, tachycardia, hypertension followed by hypotension. In children: ataxia, excitement, hallucinations.
Storage: Store at room temperature (15-30°C), protected from light and moisture. Keep in the original container, tightly closed. Keep out of reach of children and pets. Do not use after the expiry date printed on the pack.