Diphenhydramine

Antihistamine, Systemic · Antihistamine

Indications

Symptomatic relief of allergic symptoms caused by histamine release including nasal allergies and allergic dermatoses; adjunct to epinephrine in the treatment of anaphylaxis; night time sleep aid; prevention or treatment of motion sickness; antitussive; management of Parkinsonian syndrome including drug-induced extrapyramidal symptoms; topically for relief of pain and itching associated with insect bites, minor cuts and burns, or rashes due to poison ivy, poison oak and poison sumac.

Dosage

TABLET: Adults: 1-2 tabs or 25-50 mg 3-4 times daily. Max, 300 mg/day. Antitussive: Adults: 25 mg every 4 hrs. Max, 150 mg/day. SYRUP: Adults: 2 tsp 3-4 times daily. Max 150 mg/day. The night time sleep-aid dosage is 50 mg at bedtime. Children: 2-6 yr, 1/2 tsp every 4 hr. Max 37.5 mg/day; 6-12 yr, 1-2 tsp every 4 hr. Max 150 mg/day; over 12 yr, 2-4 tsp every 4 hr. Max 150 mg/day.

Adverse Effects

Dry mouth, constipation, blurred vision, drowsiness, bloating, tremor, confusion, anorexia, fatigue, weakness, restlessness, lethargy, jaundice, hepatic dysfunction, granulocytopenia, hypertension, euphoria, hallucinations, palpitations, decreased libido, ataxia, skin rash, urticaria, early menses, urinary frequency, urinary retention, purpura, eosinophilia, thrombocytopenia, agranulocytosis, nausea, vomiting, diarrhoea, weight gain, wheezing, tightness of chest, thickening of bronchial secretions.

Risk Factor (Pregnancy/Lactation)

Pregnancy: Contraindicated in pregnancy. Lactation: Contraindicated or not recommended. Contraindications: Stenosing peptic ulcer, pyloroduodenal obstruction. Precautions: Avoid driving or operate machinery cause sedation, use with caution in patients in narrow angle glaucoma, pyloroduodenal obstruction, urinary tract obstruction, hyperthyroidism, increased intraocular pressure, cardiovascular disease. Myasthenia gravis, epilepsy, prostatic hypertrophy, asthma, bronchitis, COPD. Moderate to severe renal or hepatic impairment. Risk of tolerance. Elderly.

Interactions

CNS depressants, nebivolol, tamoxifen, tramadol, amphetamines, fesoterodine, alcohol, other antihistamines, MAOIs, anticholinergics, CYP2D6 substrates.

Advice to Patient

Take with or without meals. Contact prescriber if there is agitation, confusion, urinary pattern changes, increased sleepiness, sore throat, blurred vision, difficulty in breathing, expectoration or if there is no improvement or worsening of condition. Do not take other depressants, sleep-inducing medications, alcohol without consulting prescriber. Avoid prolonged sun exposure and use a sunscreen when outside to prevent photosensitivity.

Pharmacokinetics

Duration: Histamine-induced wheal suppression: =10 hours. Histamine-induced flare suppression: =12 hours. Metabolism: Extensively hepatic; smaller degrees in pulmonary and renal systems; significant first-pass effect. Bioavailability: 42% to 62%. Half-life elimination: Children: 5 hours (range: 4 to 7 hours). Adults: 9 hours (range: 7 to 12 hours). Elderly: 13.5 hours (range: 9 to 18 hours). Time to peak, serum: Approx. 2 hours. Excretion: Urine (as metabolites and unchanged drug).

Brands with this active ingredient

• Adicos M
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• Biollin-Dm
• Brodex
• Brovenol DM
• Broxol DM
• Dexphen
• Feveren-D
• Hydeen DM
• Hydil DM
• Hydrex DM
• Hydrim
• Hydrim DM
• Hydryllin DM
• Kufzee

Compiled by Healify Pharmacy from published drug references. How we compile it →

Always consult a pharmacist or doctor.