Brand and Other Names:Dimetane, Respa-BR
- Classes: Antihistamines, 1st Generation
Dosing & Uses
Dosage Forms & Strengths
tablet extended release
- 2 mg/5mL
4 mg PO q4-6hr (no more than 24 mg qDay) PRN
Extended release: 8-12 mg tablet PO q12hr or 12-24 mg capsule PO qDay
Other Indications & Uses
Perennial & seasonal allergic & vasomotor rhinitis, relief of symptoms from colds, urticaria, angioedema, anaphylactic reactions, pruritus, allergic conjunctivitis
Dosage Forms & Strengths
Nonanticholinergic antihistamines should be considered first when treating allergic reactions (Beers Criteria)
Avoid use in elderly because of high incidence of anticholinergic effects
Clearance reduced with advanced age, greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity
May exacerbate existing lower urinary conditions or benign prostatic hyperplasia
Serious - Use Alternative
Significant - Monitor Closely
Varies in incidence & severity with the individual drug; also individual patients vary in susceptibility
Frequency Not Defined
Sedation ranging from mild drowsiness to deep sleep (most frequent)
Restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures is less common
Cholestasis, hepatitis, hepatic failure, hepatic function abnormality, jaundice is rare
Tachycardia, palpitation ECG changes (eg, widened QRS)
Arrhythmias (eg, extrasystole, heart block)
Dizziness, sedation, and hypotension may occur in geriatric patients
Dryness of mouth, nose, and throat
Tightness of the chest
Thickening of bronchial secretions
Lower respiratory disease, eg, asthma (controversial)
Preemies & neonates
Caution in narrow angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, or bladder neck obstruction
Pregnancy & Lactation
Pregnancy Category: C
Lactation: excretion in milk unknown/contraindicated
A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA:Information not available.
Mechanism of Action
Histamine H1-receptor antagonist
Half-Life: 11.8-34.7 hr
Onset: 30 min
Peak Plasma Time: 2-5 hr
Vd: 11.7 L/kg
Metabolism: mainly liver
Metabolites: Propionic acid derivative conjugated with glycine
Antihistamine activity: high
Sedative effect: Low
Anticholinergic effects: Moderate
- Antihistamine: 3-9 hr, may last 48 hr
- Antipruritic: 9-24 hr
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|1||This drug is available at the lowest co-pay. Most commonly, these are generic drugs.|
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