KARBINAL ER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for KARBINAL ER (KARBINAL ER).
Carbinoxamine is a first-generation antihistamine with anticholinergic and sedative properties. It competitively antagonizes histamine at H1 receptor sites, thereby alleviating symptoms of allergic reactions.
| Metabolism | Primarily hepatic via CYP450 isoenzymes (CYP2D6, CYP3A4); undergoes N-demethylation and oxidative deamination. |
| Excretion | Renal (approximately 50% as unchanged drug and metabolites); fecal (approximately 40%); biliary (minor). |
| Half-life | Terminal elimination half-life ranges from 20 to 30 hours, supporting once-daily dosing in extended-release formulation. |
| Protein binding | 95–99% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Approximately 10 L/kg; large Vd indicates extensive tissue distribution. |
| Bioavailability | Oral (ER): ~80% (relative to immediate-release); administration with food does not significantly alter absorption. |
| Onset of Action | Oral (ER): 2–4 hours for therapeutic effect. |
| Duration of Action | Approximately 24 hours due to extended-release formulation; steady state achieved after 5–7 days. |
Adults: 1-2 tablets (6-12 mg carbinoxamine) orally every 4-6 hours as needed; maximum 24 mg/day.
| Dosage form | SUSPENSION, EXTENDED RELEASE |
| Renal impairment | No specific guidelines. Caution in severe renal impairment (CrCl <30 mL/min) due to risk of accumulation; consider dose reduction or extended interval. |
| Liver impairment | No specific guidelines for Child-Pugh. Caution in severe hepatic impairment; consider dose reduction. |
| Pediatric use | 6-12 years: 0.2-0.4 mg/kg/day divided every 6-8 hours; max 12 mg/day. 1-6 years: 0.2-0.4 mg/kg/day divided every 6-8 hours; max 6 mg/day. |
| Geriatric use | Initiate at lowest effective dose (e.g., 1 tablet every 6-8 hours) due to increased sensitivity and risk of CNS side effects, sedation, and anticholinergic effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for KARBINAL ER (KARBINAL ER).
| Breastfeeding | Carbinoxamine is excreted into breast milk in small amounts; M/P ratio is unknown. The American Academy of Pediatrics categorizes it as compatible with breastfeeding. However, monitor infant for drowsiness or irritability. Use lowest effective dose. |
| Teratogenic Risk | Karbinal ER (carbinoxamine) is an antihistamine with limited human data. Animal studies have not shown teratogenic effects. However, first-trimester use should be cautious. In the first trimester, risk of minor malformations cannot be excluded; second and third trimesters: no known significant fetal risk. Antihistamines may cause uterine contractions if used near term. |
■ FDA Black Box Warning
Not recommended for use in pediatric patients less than 2 years of age due to risk of respiratory depression and death.
| Serious Effects |
["Hypersensitivity to carbinoxamine or any component of the formulation.","Neonates or premature infants.","Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of their discontinuation.","Significant respiratory depression, asthma attack, or angle-closure glaucoma."]
| Precautions | ["May cause drowsiness and impair mental/physical abilities; avoid driving or operating machinery.","Caution in patients with narrow-angle glaucoma, prostatic hypertrophy, bladder neck obstruction, or pyloroduodenal obstruction due to anticholinergic effects.","Avoid concurrent use with CNS depressants including alcohol.","Use in elderly may increase risk of confusion, dizziness, and hypotension.","May mask signs of ototoxicity, nephrotoxicity, or gastrointestinal symptoms."] |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of anticholinergic effects (dry mouth, urinary retention). Fetal monitoring: non-stress test and ultrasound for growth if used long-term or at high doses. Assess newborn for sedation or anticholinergic effects if used near delivery. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at clinically relevant doses. However, anticholinergic effects may theoretically alter reproductive function, but data are lacking. |