Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
VISTARIL vs ACTAHIST
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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.
Antihistamine; binds to histamine H1 receptors, blocking the effects of histamine; also exhibits anticholinergic and mild sedative properties.
Anxiety and tension associated with psychoneurosis,Pruritus due to allergic conditions (e.g., urticaria, atopic dermatitis),Sedation prior to dental or surgical procedures,Nausea and vomiting (off-label)
Symptomatic relief of allergic rhinitis,Urticaria,Off-label: motion sickness,Off-label: insomnia
Oral: 50-100 mg 4 times daily; IM: 25-100 mg every 4-6 hours as needed.
1.34 mg (one capsule) orally twice daily.
Terminal elimination half-life: 20-25 hours in adults; prolonged in hepatic impairment or elderly; steady-state achieved in ~4-5 days.
6.9 ± 1.7 hours in adults; prolonged to 12-18 hours in elderly or patients with hepatic impairment, requiring dosing interval adjustment.
Primarily hepatic via CYP3A4 and CYP2D6; major metabolites include cetirizine.
Hepatic metabolism via CYP450 enzymes (primarily CYP3A4 and CYP2D6); major metabolite is inactive.
Primarily hepatic metabolism; <1% excreted unchanged in urine; biliary/fecal elimination of metabolites accounts for approximately 50-60% of total clearance.
Primarily renal (approximately 85% as unchanged drug and metabolites) and fecal (15%) via biliary elimination.
Highly protein-bound: approximately 89-93%, primarily to albumin.
92% bound to albumin.
Volume of distribution: 7-10 L/kg, indicating extensive tissue distribution.
0.9 ± 0.3 L/kg, indicating extensive extravascular distribution.
Oral: incomplete bioavailability due to first-pass metabolism, estimated at 40-60%; IM: nearly complete (85-100%).
Oral: 68% ± 12% due to first-pass metabolism.
No specific adjustment; use with caution in severe renal impairment due to potential accumulation of metabolites.
No dose adjustment required for mild to moderate renal impairment. Safety not established for severe impairment (GFR <30 m L/min).
Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use.
No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not recommended for severe hepatic impairment (Child-Pugh C).
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.
Not indicated for pediatric patients under 12 years of age. Safety and efficacy not established.
Start at lower end of dosing range (e.g., 25 mg oral 3-4 times daily); monitor for sedation and anticholinergic effects.
No specific dose adjustment recommended; monitor for increased anticholinergic effects and cognitive impairment.
No FDA black box warning.
None.
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
May cause drowsiness; caution when driving or operating machinery. Avoid alcohol. Use with caution in patients with narrow-angle glaucoma, prostatic hyperplasia, or urinary retention. Geriatric patients more sensitive to anticholinergic effects. Pediatric patients <6 years: not recommended.
Hypersensitivity to hydroxyzine or any component,Early pregnancy (first trimester),Porphyria,Breastfeeding (use caution)
Hypersensitivity to any component. Newborns or premature infants. Breastfeeding (contraindicated due to risk of adverse effects in infants). Concomitant use with MAOIs.
Alcohol increases sedation and CNS depression; avoid concurrent use. No significant food interactions, but take with food if GI upset occurs.
Avoid high-tyramine foods (aged cheese, cured meats, fermented products) if taking MAOIs. Grapefruit juice may increase phenylephrine absorption; limit intake.
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.
ACTAHIST (brompheniramine/phenylephrine) pregnancy category C. Inadequate human data; animal studies show no malformations at therapeutic doses. First trimester: theoretical risk from vasoconstrictive effects (phenylephrine) possibly reducing uterine blood flow; avoid if possible. Second/third trimester: phenylephrine may cause fetal hypoxia via placental vasoconstriction; use only if benefit outweighs risk. No known structural teratogenicity.
Hydroxyzine is excreted in human milk; M/P ratio not established. Potential for adverse effects in infants (sedation, irritability). Use during breastfeeding only if clearly needed; monitor infant for drowsiness.
Brompheniramine is excreted in breast milk in small amounts; M/P ratio not established. Phenylephrine has minimal excretion. Due to anticholinergic effects, may reduce milk production or cause sedation in infants. Use caution; prefer non-sedating alternatives if possible.
No specific dose adjustments recommended in pregnancy; use lowest effective dose. Hydroxyzine may be less effective if used as an antiemetic due to altered clearance; consider alternative agents.
No specific pharmacokinetic studies. Increased plasma volume and renal clearance in pregnancy may reduce drug levels, but efficacy threshold remains. No dose adjustment recommended; use the lowest effective dose for shortest duration due to potential risks.
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.
Actahist is a combination antihistamine-decongestant (chlorpheniramine/phenylephrine). Avoid in patients with hypertension, severe coronary artery disease, or MAOI use. Monitor for sedation and urinary retention, especially in elderly males with BPH.
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.
Take with food or milk to reduce stomach upset.,Avoid alcohol and CNS depressants as they can increase drowsiness.,Do not drive or operate machinery until you know how this medication affects you.,Contact your doctor if you experience chest pain, rapid heartbeat, or difficulty urinating.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about VISTARIL vs ACTAHIST, answered by our medical review team.
VISTARIL is a Antihistamine that works by 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.. ACTAHIST is a Antihistamine that works by Antihistamine; binds to histamine H1 receptors, blocking the effects of histamine; also exhibits anticholinergic and mild sedative properties.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between VISTARIL and ACTAHIST depend on the specific clinical indication. These are both Antihistamine agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of VISTARIL is: Oral: 50-100 mg 4 times daily; IM: 25-100 mg every 4-6 hours as needed.. The standard adult dose of ACTAHIST is: 1.34 mg (one capsule) orally twice daily.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between VISTARIL and ACTAHIST in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. VISTARIL is classified as Category C. 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 w. ACTAHIST is classified as Category C. ACTAHIST (brompheniramine/phenylephrine) pregnancy category C. Inadequate human data; animal studies show no malformations at therapeutic doses. First trimester: theoretical risk f. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.