hydroxyzine VISTARIL/ATARAX
Class: Antihistamine/PiperazineFDA Indications: Anxiety Disorders, Pruritis Due To Allergic Conditions, Acute Disturbance Or Hysteria (IM), Nausea And Vomiting (IM)
Off-Label Use: Insomnia
Prescribing
Forms: 10, 25, 50, 100mg tablet; 25, 50, 100mg capsule; 10mg/5mL, 25mg/5mL po soln; 25mg/mL, 50mg/mL injectable mg/dayStarting: 50-100 mg po tid
Precautions
Contraindications: Avoid in elderly patients with dementiaConditional Risk of TdP
Side Effects: sedation/somnolence, dizziness, confusion, anticholinergic side effects, ataxia
Pharmacokinetics
t½: 20 (16-24)° TMAX: 2°Substrate of: 2D6
Inhibits: ∅ ; Induces: ∅
Active Metabolites: Cetirizine (Zyrtec)
DDIs
- - co-prescribed 2D6 inhibitors can ↑ serum levels
- - caution when prescribing with other CNS depressants
- - caution with other anticholinergic agents
Misc
- - preferred anxiolytic for patients with pruritis (dermatologic or psychogenic)
- - no abuse potential
- - the ratio of affinity for H1 to M1 is more than 10 times greater than diphenhydramine, i.e. a much less anticholinergic alternative to diphenhydramine
- - a disadvantage to using as a sleep aid is its comparatively long t½ which can lead to daytime sedation
Special Populations
Category Not classified.—In animal studies, high doses of hydroxyzine were associated with developmental toxicity (structural anomalies and death), but the human data suggest low risk. Although a surveillance study found an increased risk of oral clefts, this defect has not been observed in other studies. Withdrawal or seizures have been reported in two newborns exposed near term.
No reports describing the use of hydroxyzine during lactation have been located. The molecular weight (about 448) is low enough that excretion into breast milk should be expected. The effects, if any, on the nursing infant are unknown.
Initiate dosing at lower end of recommended dose range as it may cause oversedation.
2019 BEE℞S Recommendation: Avoid. Highly anticholinergic; clearance reduced with advanced age, and tolerance develops when used as hypnotic; risk of confusion, dry mouth, constipation, and other anticholinergic effects or toxicity.
GFR > 50mL/min, no adjustment
GFR ≤ 50 ml/min, ↓ dose 50%
No adjustments necessary except for cases of 1° biliary cirrhosis, Δ dosing to Q24