HOMAPIN-5
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HOMAPIN-5 (HOMAPIN-5).
Homapin-5 is a combination product containing homatropine methylbromide, an antimuscarinic agent that inhibits the action of acetylcholine at muscarinic receptors, reducing gastrointestinal motility and secretion.
| Metabolism | Homatropine methylbromide is poorly absorbed and undergoes limited metabolism; primarily excreted unchanged in feces and urine. |
| Excretion | Renal: 70% unchanged; biliary/fecal: 20% as metabolites; 10% as metabolites in urine. |
| Half-life | Terminal half-life 3-5 hours; clinically effective half-life 4 hours for motor response in Parkinson's disease. |
| Protein binding | 50% bound primarily to albumin. |
| Volume of Distribution | 1.5-3.0 L/kg; indicates extensive tissue distribution, including CNS. |
| Bioavailability | Oral: 30-50% (first-pass metabolism); IM: 100%. |
| Onset of Action | Oral: 30 minutes; intravenous: 5 minutes; intramuscular: 15 minutes. |
| Duration of Action | Oral: 4-6 hours; IV/IM: 2-4 hours; sustained-release up to 8 hours. Duration shorter with disease progression. |
Adults: 5 mg orally every 6 to 8 hours as needed for nausea and vomiting.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (CrCl <30 mL/min) due to potential for prolonged effects. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B or C: Reduce dose by 50% and extend dosing interval to every 12 hours. |
| Pediatric use | Children 12 years and older: 5 mg orally every 6 to 8 hours as needed. Children under 12 years: Not recommended due to lack of safety data. |
| Geriatric use | Elderly patients may be more sensitive to anticholinergic effects; initiate at lower dose (2.5 mg every 8 hours) and titrate cautiously. Monitor for confusion and urinary retention. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HOMAPIN-5 (HOMAPIN-5).
| Breastfeeding | Unknown if excreted in human milk. M/P ratio not established. Due to potential for serious adverse reactions in nursing infants, decision should be made to discontinue nursing or discontinue drug, taking into account importance of drug to mother. |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: increased risk of congenital malformations, particularly cardiovascular and cleft palate. Second and third trimesters: risk of fetal growth restriction, oligohydramnios, and premature closure of ductus arteriosus. Avoid in pregnancy unless no alternative. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to any component, glaucoma (narrow-angle), obstructive uropathy, obstructive gastrointestinal disease, myasthenia gravis, paralytic ileus, severe ulcerative colitis.
| Precautions | May cause drowsiness, blurred vision, and dry mouth; use with caution in glaucoma, prostatic hypertrophy, and hepatic/renal impairment; avoid in patients with gastrointestinal obstruction or myasthenia gravis. |
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| Fetal Monitoring |
| Monitor maternal blood pressure, heart rate, and renal function. Fetal ultrasound for growth and amniotic fluid volume. Nonstress test or biophysical profile as clinically indicated. Consider echocardiography for fetal cardiac effects. |
| Fertility Effects | Animal studies show reduced fertility at high doses. Human data limited; may impair spermatogenesis or ovulation. Reversible upon discontinuation. |