Dosing & Uses
Dosage Forms & Strengths
25 mg PO qHS PRN 30 min before bedtime
Upper Respiratory Tract Allergy
50 mg PO q4-6hr
<12 years: Not recommended
>12 years: 25 mg PO qHS PRN 30 min before bedtime
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
Tolerance develops when used as hypnotic
Serious - Use Alternative
Significant - Monitor Closely
Frequency Not Defined
Minor anticholinergic effects
May cause CNS depression, which may impair physical and mental activities
Not to exceed 2 weeks of use
Caution in asthma, glaucoma, enlarged prostate, cardiovascular disease, respiratory disease, or thyroid dysfunction
Pregnancy & Lactation
Pregnancy Category: B
Lactation: excretion in milk unknown
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
Competes for H1-receptor sites on target cells; has anticholinergic effects, which depresses labyrinthine function, blocks chemoreceptor trigger zone, and diminishes vestibular stimulation
Peak Plasma Time: 2-3 hr
Peak Plasma Concentration: 100 ng/mL
Half-Life: 10-12 hr