VISTARIL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VISTARIL (VISTARIL).
Hydroxyzine is a piperazine derivative antihistamine that acts as a competitive antagonist of histamine H1 receptors, thereby suppressing histamine activity in the subcortical area of the central nervous system. It also has anxiolytic, sedative, antiemetic, and antispasmodic effects.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2D6; major metabolites include cetirizine. |
| Excretion | Primarily hepatic metabolism; <1% excreted unchanged in urine; biliary/fecal elimination of metabolites accounts for approximately 50-60% of total clearance. |
| Half-life | Terminal elimination half-life: 20-25 hours in adults; prolonged in hepatic impairment or elderly; steady-state achieved in ~4-5 days. |
| Protein binding | Highly protein-bound: approximately 89-93%, primarily to albumin. |
| Volume of Distribution | Volume of distribution: 7-10 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: incomplete bioavailability due to first-pass metabolism, estimated at 40-60%; IM: nearly complete (85-100%). |
| Onset of Action | Oral: 15-30 minutes; IM: 15-30 minutes; IV: within 5 minutes. |
| Duration of Action | Oral: 4-6 hours (anxiolytic), 24 hours (antihistamine); IM/IV: 4-6 hours (anxiolytic/sedative). |
| Molecular Weight | 447.83 |
Oral: 50-100 mg 4 times daily; IM: 25-100 mg every 4-6 hours as needed.
| Dosage form | CAPSULE |
| Renal impairment | No specific adjustment; use with caution in severe renal impairment due to potential accumulation of metabolites. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use. |
| Pediatric use | Oral: 0.5-1 mg/kg every 4-6 hours; maximum 50 mg per dose (≤12 years); IM: 0.5-1 mg/kg every 4-6 hours. |
| Geriatric use | Start at lower end of dosing range (e.g., 25 mg oral 3-4 times daily); monitor for sedation and anticholinergic effects. |
| 1st trimester | Teratogenic effects observed in animal studies, but no well-controlled human studies. Use only if potential benefit justifies potential risk to fetus. |
| 2nd trimester | May cause fetal harm; avoid use during pregnancy, especially during organogenesis. |
| 3rd trimester | May cause neonatal respiratory depression, hypotonia, and withdrawal symptoms if used near term. Avoid use in late pregnancy. |
Clinical note
Comprehensive clinical and safety monograph for VISTARIL (VISTARIL).
| Placental transfer | Hydroxyzine crosses the placenta; detectable levels in fetal plasma have been reported. |
| Breastfeeding | Hydroxyzine is excreted into breast milk in small amounts; however, potential for serious adverse reactions in nursing infants exists. Use with caution, and consider the developmental and health benefits of breastfeeding along with the mother's clinical need for the drug. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to hydroxyzine or any of its componentsEarly pregnancy (first trimester) and established pregnancy
| Precautions | May cause QT prolongation; use with caution in patients with risk factors (e.g., electrolyte imbalance, concomitant QT-prolonging drugs), Sedation and impaired cognitive/motor function; avoid driving or hazardous activities, Anticholinergic effects (e.g., urinary retention, constipation); use cautiously in elderly or patients with prostatic hypertrophy, Respiratory depression with concurrent CNS depressants, Use in pregnancy: avoid especially during early pregnancy; may increase risk of fetal abnormalities |
| Food/Dietary | Alcohol increases sedation and CNS depression; avoid concurrent use. No significant food interactions, but take with food if GI upset occurs. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited human data; animal studies suggest no major teratogenic risk; fetal harm cannot be ruled out. Second and third trimesters: Hydroxyzine may cause neonatal withdrawal symptoms (irritability, tremors) with chronic maternal use near term; no evidence of structural anomalies. |
| Fetal Monitoring | Monitor maternal vital signs and level of sedation; assess fetal heart rate and uterine activity if used during labor; observe neonate for respiratory depression and withdrawal symptoms after delivery. |
| Fertility Effects | No specific studies on human fertility; animal studies show no significant reproductive impairment at clinically relevant doses. |
| Clinical Pearls | VISTARIL (hydroxyzine pamoate) is a first-generation antihistamine with anxiolytic and sedative properties. It is often used for preoperative sedation, pruritus, and anxiety. Onset of sedation is rapid (15-30 minutes) but duration is short (4-6 hours). It has anticholinergic effects; caution in elderly and patients with glaucoma or prostatic hypertrophy. Do not administer intra-arterially or subcutaneously (risk of hemolysis or tissue necrosis). It is not a controlled substance, but has abuse potential. May cause significant somnolence; advise against driving or operating machinery. |
| Patient Advice | Take as prescribed; do not exceed recommended dose. · May cause drowsiness; avoid driving or heavy machinery until you know how it affects you. · Avoid alcohol and other CNS depressants. · Report any signs of allergic reaction (rash, difficulty breathing) immediately. · Do not stop abruptly without consulting doctor. · Store at room temperature away from moisture and heat. |