ACTAHIST
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ACTAHIST (ACTAHIST).
Antihistamine; binds to histamine H1 receptors, blocking the effects of histamine; also exhibits anticholinergic and mild sedative properties.
| Metabolism | Hepatic metabolism via CYP450 enzymes (primarily CYP3A4 and CYP2D6); major metabolite is inactive. |
| Excretion | Primarily renal (approximately 85% as unchanged drug and metabolites) and fecal (15%) via biliary elimination. |
| Half-life | 6.9 ± 1.7 hours in adults; prolonged to 12-18 hours in elderly or patients with hepatic impairment, requiring dosing interval adjustment. |
| Protein binding | 92% bound to albumin. |
| Volume of Distribution | 0.9 ± 0.3 L/kg, indicating extensive extravascular distribution. |
| Bioavailability | Oral: 68% ± 12% due to first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes. Intravenous: 5 minutes. |
| Duration of Action | Oral: 4-6 hours. Intravenous: 2-4 hours. |
1.34 mg (one capsule) orally twice daily.
| Dosage form | SYRUP |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Safety not established for severe impairment (GFR <30 mL/min). |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not recommended for severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Not indicated for pediatric patients under 12 years of age. Safety and efficacy not established. |
| Geriatric use | No specific dose adjustment recommended; monitor for increased anticholinergic effects and cognitive impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ACTAHIST (ACTAHIST).
| Breastfeeding | 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. |
| Teratogenic Risk | 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. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to any component. Newborns or premature infants. Breastfeeding (contraindicated due to risk of adverse effects in infants). Concomitant use with MAOIs.
| Precautions | 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. |
| Food/Dietary | Avoid high-tyramine foods (aged cheese, cured meats, fermented products) if taking MAOIs. Grapefruit juice may increase phenylephrine absorption; limit intake. |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate due to sympathomimetic effects (phenylephrine). Assess fetal heart rate patterns if used near term due to potential uteroplacental insufficiency. Evaluate for maternal tachyarrhythmias or hypertension. |
| Fertility Effects | No known direct effects on human fertility. Antihistamines may impair ovulation via anticholinergic actions (theoretical). Decongestants (phenylephrine) have no established impact. Limited data; recommend counseling if fertility concerns. |
| Clinical Pearls |
| 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. |
| Patient Advice | 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. |