Indications/Uses
Listed in Dosage.
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Dosage/Direction for Use
Adult: PO Allergic conditions; Motion sickness 25-50 mg 3 or 4 times/day. Max: 300 mg/day. For prevention of motion sickness, administer 30 minutes before exposure to motion. Short-term management of insomnia 50 mg given 30 minutes before bedtime as needed. IV/IM Allergic conditions; Motion sickness; Parkinson's disease 10-50 mg up to 100 mg if needed, via IV inj at a rate of 25 mg/min or deep IM inj. Max: 400 mg/day. For prevention of motion sickness, administer 30 minutes before exposure to motion. Topical/Cutaneous Pruritic skin disorders As 2% cream: Apply to affected area(s) up to max bid for not more than 3 days.
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Administration
May be taken with or without food.
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Contraindications
Stenosing peptic ulcer or pyloroduodenal obstruction. Premature infants and neonates. Lactation. Concomitant use with other antihistamine-containing medicines (including topical antihistamines).
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Special Precautions
Patient with narrow-angle glaucoma, prostatic hypertrophy or genitourinary obstruction, urinary retention, asthma, bronchitis, COPD, CV (e.g. hypertension, ischaemic heart disease), thyroid disorder, myasthenia gravis, seizure disorders (e.g. epilepsy). Moderate to severe renal and hepatic impairment. Elderly. Pregnancy. Patient Counselling This drug may cause drowsiness or sedation, dizziness, blurred vision, cognitive and psychomotor impairment, if affected, do not drive or operate machinery. Monitoring Parameters Monitor mental alertness.
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Adverse Reactions
Significant: Drug tolerance (continuous use). Rarely, eczematous reactions (topical).
Blood and lymphatic system disorders: Haemolytic anaemia, thrombocytopenia, agranulocytosis.
Cardiac disorders: Palpitations, tachycardia, extrasystoles.
Gastrointestinal disorders: Dry mouth, epigastric distress, nausea, vomiting, diarrhoea, constipation.
General disorders and administration site conditions: Fatigue.
Metabolism and nutrition disorders: Anorexia.
Nervous system disorders: Sedation, drowsiness, restlessness, dizziness, excitability (children), headache.
Psychiatric disorders: Disturbance in attention, confusion, nervousness.
Renal and urinary disorders: Urinary frequency, urinary retention, difficulty in micturition.
Respiratory, thoracic and mediastinal disorders: Thickening of bronchial secretions.
Skin and subcutaneous tissue disorders: Sensitisation reaction, photosensitivity.
Vascular disorders: Hypotension.
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Drug Interactions
May increase sedative effects of other CNS depressants (e.g. tranquilizers, hypnotics, anxiolytics). Enhanced and prolonged anticholinergic effects with MAOIs. May potentiate effects of anticholinergic agents (e.g. atropine, TCA). May diminish therapeutic effect of betahistine.
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ATC Classification
D04AA32 - diphenhydramine ; Belongs to the class of topical antihistamines used in the treatment of pruritus.
R06AA02 - diphenhydramine ; Belongs to the class of aminoalkyl ethers used as systemic antihistamines. |