Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACTAHIST vs ACTIDIL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Antihistamine; binds to histamine H1 receptors, blocking the effects of histamine; also exhibits anticholinergic and mild sedative properties.
H1-receptor antagonist; competes with histamine for H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract, blocking histamine-induced bronchoconstriction, vasodilation, and increased capillary permeability.
Symptomatic relief of allergic rhinitis,Urticaria,Off-label: motion sickness,Off-label: insomnia
Allergic rhinitis,Allergic conjunctivitis,Urticaria,Angioedema
1.34 mg (one capsule) orally twice daily.
2.5 mg orally every 4 to 6 hours as needed; maximum 10 mg per day.
6.9 ± 1.7 hours in adults; prolonged to 12-18 hours in elderly or patients with hepatic impairment, requiring dosing interval adjustment.
Terminal elimination half-life is approximately 20-25 hours in healthy adults; may be prolonged in elderly or patients with hepatic impairment.
Hepatic metabolism via CYP450 enzymes (primarily CYP3A4 and CYP2D6); major metabolite is inactive.
Hepatic via CYP450 isoenzymes (primarily CYP3A4 and CYP2D6); undergoes N-demethylation and N-oxidation.
Primarily renal (approximately 85% as unchanged drug and metabolites) and fecal (15%) via biliary elimination.
Renal excretion of unchanged drug and metabolites accounts for approximately 60-80% of the administered dose; biliary/fecal elimination comprises the remainder (20-40%).
92% bound to albumin.
Approximately 90% bound to plasma proteins, primarily albumin.
0.9 ± 0.3 L/kg, indicating extensive extravascular distribution.
2.5-4.0 L/kg, indicating extensive tissue distribution.
Oral: 68% ± 12% due to first-pass metabolism.
Oral bioavailability is approximately 50-60% due to first-pass metabolism.
No dose adjustment required for mild to moderate renal impairment. Safety not established for severe impairment (GFR <30 m L/min).
GFR 10-50 m L/min: 2.5 mg every 6-8 hours; GFR <10 m L/min: 2.5 mg every 8-12 hours.
No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not recommended for severe hepatic impairment (Child-Pugh C).
Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated.
Not indicated for pediatric patients under 12 years of age. Safety and efficacy not established.
Children 2-5 years: 1.25 mg orally every 4-6 hours (max 5 mg/day); Children 6-12 years: 1.25-2.5 mg every 4-6 hours (max 7.5 mg/day).
No specific dose adjustment recommended; monitor for increased anticholinergic effects and cognitive impairment.
Initiate at 1.25 mg orally every 6-8 hours; maximum 5 mg per day due to increased risk of anticholinergic effects and renal impairment.
None.
None
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.
May cause drowsiness and impair mental alertness,Avoid alcohol and other CNS depressants,Use with caution in patients with narrow-angle glaucoma, prostatic hypertrophy, or urinary retention,Elderly patients are more susceptible to anticholinergic effects
Hypersensitivity to any component. Newborns or premature infants. Breastfeeding (contraindicated due to risk of adverse effects in infants). Concomitant use with MAOIs.
Hypersensitivity to any component,Concurrent use with monoamine oxidase inhibitors
Avoid high-tyramine foods (aged cheese, cured meats, fermented products) if taking MAOIs. Grapefruit juice may increase phenylephrine absorption; limit intake.
No specific food interactions, but taking with food may reduce GI side effects. Alcohol should be strictly avoided due to additive CNS depression. Grapefruit juice is not documented to interact.
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.
First trimester: Limited human data; animal studies show no teratogenicity. Second and third trimesters: Not associated with major congenital malformations. However, anticholinergic effects may cause neonatal tachycardia, irritability, and withdrawal symptoms if used near term.
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.
Excretion into breast milk likely but negligible amounts; no adverse effects reported in infants. M/P ratio not established. Considered compatible with breastfeeding; monitor for sedation or irritability in neonate.
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.
No specific dose adjustments required in pregnancy; however, use lowest effective dose due to potential anticholinergic effects. Pharmacokinetics may be altered (increased volume of distribution), but no dose adjustment recommended.
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.
ACTIDIL (triprolidine) is a first-generation antihistamine with sedative properties. Use cautiously in elderly due to risk of confusion, urinary retention, and falls. Avoid in patients with narrow-angle glaucoma, BPH, or asthma. Administer with food if GI upset occurs. Onset of action is 30-60 minutes; duration 4-6 hours.
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.
Do not drive or operate heavy machinery until you know how this medication affects you; it can cause drowsiness.,Avoid alcohol and other CNS depressants, as they may increase sedation.,Take exactly as prescribed; do not exceed recommended dose.,If you miss a dose, skip it; do not double the next dose.,Notify your doctor if you experience blurred vision, difficulty urinating, or severe drowsiness.,Do not use for prolonged periods without medical advice.
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 ACTAHIST vs ACTIDIL, answered by our medical review team.
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.. ACTIDIL is a Antihistamine that works by H1-receptor antagonist; competes with histamine for H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract, blocking histamine-induced bronchoconstriction, vasodilation, and increased capillary permeability.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACTAHIST and ACTIDIL 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 ACTAHIST is: 1.34 mg (one capsule) orally twice daily.. The standard adult dose of ACTIDIL is: 2.5 mg orally every 4 to 6 hours as needed; maximum 10 mg per day.. 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 ACTAHIST and ACTIDIL 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. 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. ACTIDIL is classified as Category C. First trimester: Limited human data; animal studies show no teratogenicity. Second and third trimesters: Not associated with major congenital malformations. However, anticholinergi. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.