DISOMER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DISOMER (DISOMER).
Selective dopamine D2 receptor antagonist; also blocks alpha-1 adrenergic, histamine H1, and muscarinic M1 receptors.
| Metabolism | Hepatic via CYP2D6 and CYP3A4; some metabolism via carbonyl reduction. |
| Excretion | Renal: 80% as unchanged drug; biliary/fecal: 15% as metabolites; <5% unchanged in feces. |
| Half-life | 12–15 hours in adults with normal renal function; prolonged to 30–40 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | 92% bound to albumin; minor binding to α1-acid glycoprotein. |
| Volume of Distribution | 1.8 L/kg indicating extensive extravascular distribution. |
| Bioavailability | Oral: 75% (range 60–85%) due to moderate first-pass metabolism. |
| Onset of Action | Oral: 30–60 minutes; IV: <5 minutes. |
| Duration of Action | 8–12 hours following oral administration; 6–8 hours after IV dosing; extended in renal impairment. |
Adults: 1 mg orally once daily.
| Dosage form | SYRUP |
| Renal impairment | CrCl 30-89 mL/min: no adjustment; CrCl 15-29 mL/min: 0.5 mg orally once daily; CrCl <15 mL/min or dialysis: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 0.5 mg orally once daily; Child-Pugh C: contraindicated. |
| Pediatric use | Children 6-17 years: 0.02 mg/kg orally once daily, max 1 mg/day. |
| Geriatric use | Initiate at 0.5 mg orally once daily; titrate cautiously due to increased sensitivity and renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DISOMER (DISOMER).
| Breastfeeding | DISOMER is excreted into breast milk in low concentrations. The M/P ratio is not well established. Clinical studies suggest infant doses of approximately 0.1-0.5% of the maternal weight-adjusted dose. Caution is advised; monitor infant for sedation or respiratory depression. |
| Teratogenic Risk | DISOMER (dextromethorphan) is not associated with major congenital malformations. Available data do not indicate an increased risk of teratogenicity in the first trimester. Second and third trimester use may be associated with a low risk of neonatal respiratory depression if used in high doses or near term. |
■ FDA Black Box Warning
Increased mortality in elderly patients with dementia-related psychosis.
| Serious Effects |
["Hypersensitivity to disomer","History of neuroleptic malignant syndrome","Concurrent use with QT-prolonging drugs (risk of torsades de pointes)"]
| Precautions | ["Tardive dyskinesia","Neuroleptic malignant syndrome","Hyperglycemia and diabetes mellitus","Orthostatic hypotension","Leukopenia/neutropenia/agranulocytosis"] |
| Food/Dietary | Avoid alcohol consumption during therapy as it may enhance CNS depression. No other significant food interactions are known. Grapefruit juice does not affect metabolism. Take with food if gastrointestinal upset occurs. |
Loading safety data…
| Fetal Monitoring | Monitor maternal respiratory status, sedation levels, and fetal heart rate patterns during prolonged or high-dose use. Assess neonatal Apgar scores and respiratory function after delivery if used near term. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies have not shown significant reproductive toxicity at therapeutic doses. |
| Clinical Pearls |
| DISOMER (dexchlorpheniramine maleate) is a first-generation antihistamine with strong sedative properties. Use with caution in elderly patients due to increased risk of confusion, urinary retention, and falls. Avoid in patients with narrow-angle glaucoma, prostatic hyperplasia, or bladder neck obstruction. Onset of action is 15-30 minutes; duration is 4-6 hours. May cause paradoxical excitation in children. Potentiates CNS depression with alcohol, sedatives, and tranquilizers. |
| Patient Advice | Do not drive or operate heavy machinery until you know how this medication affects you, as it may cause drowsiness. · Avoid alcohol consumption while taking this medication, as it can increase sedation. · Notify your doctor if you have glaucoma, difficulty urinating, or enlarged prostate before taking DISOMER. · Take this medication exactly as prescribed; do not exceed the recommended dose. · If you miss a dose, take it as soon as you remember unless it is almost time for the next dose; do not double up. · Store at room temperature away from moisture and heat. |