Oral Prophylaxis of cluster headache, Prophylaxis of migraine
Adult: Initially, 0.5 mg once daily. May increase dose gradually according to tolerability and response. Maintenance dose: 1.5 mg single dose at night or in 3 divided doses. Max single dose: 3 mg; Max daily dose: 4.5 mg. Child: 2 years Initially, 0.5 mg once daily. May increase dose up to 1.5 mg daily in divided doses. Max single dose: 1 mg (at night).
Renal Impairment
Dosage adjustment may be needed.
Hepatic Impairment
Dosage adjustment may be needed.
Administration
May be taken with or without food.
Special Precautions
Patient with epilepsy, closed angle glaucoma; at risk of or with current urinary retention (e.g. prostate hypertrophy). Obese patient. Not indicated for the treatment of migraine attacks or tension headaches. Avoid abrupt withdrawal. Renal and hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: CNS depression, hepatotoxicity, increased appetite, weight gain. Rarely, seizures. Gastrointestinal disorders: Nausea, vomiting, dry mouth. General disorders and administration site conditions: Fatigue. Musculoskeletal and connective tissue disorders: Arthralgia, muscle cramps. Nervous system disorders: Somnolence, dizziness, drowsiness, tremor. Psychiatric disorders: Rarely, depression, anxiety, insomnia. Skin and subcutaneous tissue disorders: Rarely, rash, urticaria.
Patient Counseling Information
This drug may cause dizziness, somnolence, or vertigo; if affected, do not drive or operate machinery.
Symptoms: Nausea, vomiting, xerostomia, drowsiness, dizziness, hypotension, tachycardia, pyrexia, confusion, ataxia, dyspnoea, cyanosis, respiratory paraylysis, coma; excitatory states, convulsions (particularly in children). Management: Symptomatic treatment. Administer activated charcoal; may perform gastric lavage in case of very recent intake. Short-acting barbiturates or benzodiazepines may be given for excitatory states or convulsions. Correct severe hypotension.
Drug Interactions
May diminish the therapeutic effect of cisapride. Increased central effects of sedatives, hypnotics, antihistamines. Decreased hypotensive effect of adrenergic neurone blockers (e.g. debrisoquine, guanethidine).
Food Interaction
Increased central effects of alcohol.
Action
Description: Mechanism of Action: Pizotifen is a potent serotonin and tryptamine inhibitor with weak antihistamine, anticholinergic, and antikinin effects; it also possesses appetite-stimulating and sedative properties. The mechanism of action by which it exerts its prophylactic effect on migraine has not been fully explained but has been associated with its capability to modify the humoral mechanisms of headache. It prevents the permeability-increasing effect of serotonin and histamine on the affected cranial vessels, thereby regulating the transudation of plasmakinin which maintains the pain threshold of receptors at the normal levels. It inhibits serotonin reuptake by platelets which affects tonicity and reduces the passive distension of extracranial arteries. Onset: Weeks of therapy may be needed. Pharmacokinetics: Absorption: Rapidly and almost completely absorbed from the gastrointestinal tract. Bioavailability: Approx 78%. Time to peak plasma concentration: Approx 5 hours. Distribution: Extensively and rapidly distributed throughout the body. Volume of distribution: 833 L (parent drug); 70 L (N-glucuronide metabolite). Plasma protein binding: Approx 91%. Metabolism: Extensively metabolised in the liver via glucuronidation into its major metabolite N-glucoronide-conjugate. Excretion: Mainly via urine (approx 55% as metabolites, <1% as unchanged drug); faeces (approx 33% of dose). Elimination half-life: Approx 23 hours (parent drug and metabolite).
Chemical Structure
Pizotifen Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 27400, Pizotifen. https://pubchem.ncbi.nlm.nih.gov/compound/Pizotifen. Accessed Apr. 27, 2023.
Storage
Store between 15-30°C. Protect from light and moisture.
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