ISOCLOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOCLOR (ISOCLOR).
Chlorpheniramine is an antihistamine (H1-receptor antagonist) that blocks the action of histamine, reducing allergy symptoms. Pseudoephedrine is a sympathomimetic amine that acts as a decongestant by stimulating alpha-adrenergic receptors, causing vasoconstriction in the nasal mucosa.
| Metabolism | Chlorpheniramine: Hepatic metabolism via CYP2D6 and other enzymes. Pseudoephedrine: Hepatic metabolism via N-demethylation and oxidative metabolism. |
| Excretion | Primarily renal; approximately 60-70% of a dose excreted unchanged in urine within 24 hours. Biliary/fecal excretion accounts for <10%. |
| Half-life | Approximately 2-4 hours in patients with normal renal function; prolonged to 8-12 hours in renal impairment (CrCl <30 mL/min). |
| Protein binding | Approximately 70-75% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 1.5-2.0 L/kg, indicating extensive extravascular distribution. |
| Bioavailability | Oral: approximately 70-80% (first-pass metabolism reduces bioavailability from complete absorption). Topical: minimal systemic absorption (<5% with intact skin). |
| Onset of Action | Oral: 30-60 minutes; topical: 15-30 minutes. |
| Duration of Action | Oral: 2-4 hours (clinical effect wanes by 4-6 hours). Topical: 2-4 hours. |
| Molecular Weight | Chlorpheniramine: 274.8 Da; Pseudoephedrine: 165.2 Da |
Oral: 1 tablet (chlorpheniramine 4 mg / pseudoephedrine 60 mg) every 4-6 hours, not to exceed 4 tablets per 24 hours.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | GFR 30-50 mL/min: Administer every 8-12 hours. GFR 10-29 mL/min: Administer every 12 hours. GFR <10 mL/min: Not recommended; avoid use. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Dose cautiously, monitor for CNS depression. Child-Pugh Class C: Contraindicated. |
| Pediatric use | Children 6-12 years: 1/2 tablet (chlorpheniramine 2 mg / pseudoephedrine 30 mg) every 4-6 hours, not to exceed 3 doses per day. Children <6 years: Not recommended. |
| Geriatric use | Initiate with 1/2 tablet every 8 hours due to increased sensitivity to anticholinergic effects and CNS depression; monitor closely. |
| 1st trimester | Avoid use; potential teratogenic effects reported with sympathomimetics and antihistamines. |
| 2nd trimester | Use only if clearly needed; may cause uterine vasoconstriction and fetal hypoxia. |
| 3rd trimester | Avoid near term; risk of neonatal hemorrhage with antihistamines and tachycardia with sympathomimetics. |
Clinical note
Comprehensive clinical and safety monograph for ISOCLOR (ISOCLOR).
| Placental transfer | Both components cross the placenta; pseudoephedrine has documented transfer in animal studies. |
| Breastfeeding | Chlorpheniramine and pseudoephedrine are excreted into breast milk in small amounts. Pseudoephedrine may reduce milk production. Use with caution; monitor infant for irritability and sleep disturbances. |
| Lactation Rating |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to any componentSevere hypertensionCoronary artery diseaseConcurrent MAOI therapy or within 14 daysNarrow-angle glaucomaUrinary retentionSevere hepatic impairment
| Precautions | Cardiovascular effects: hypertension, palpitations, tachycardia, arrhythmias, CNS effects: nervousness, dizziness, insomnia, especially in children, Use with caution in patients with cardiovascular disease, hypertension, hyperthyroidism, diabetes, or prostatic hypertrophy, Avoid use in patients with severe hypertension or coronary artery disease, Do not exceed recommended dosage, Not for use in children under 12 years without medical advice |
| Food/Dietary | Avoid alcohol. Caffeine may increase stimulant effects. Taking with food may reduce GI upset but delay onset. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category C (as combination product). In first trimester, animal studies show fetal harm; limited human data. Risk of neural tube defects with folic acid antagonists. Avoid in first trimester if possible. Second/third trimester: risk of premature closure of ductus arteriosus and neonatal pulmonary hypertension with decongestant component; avoid near term. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate due to decongestant cardiovascular effects. Assess for signs of premature labor. Fetal ultrasound for growth and ductus arteriosus patency if used after 20 weeks. |
| Fertility Effects | Limited data; antihistamines may impair fertility by altering cervical mucus and tubal function. Decongestants may reduce uterine blood flow. No specific human fertility studies. |
| Clinical Pearls | Isoclor is a combination of chlorpheniramine (antihistamine) and pseudoephedrine (decongestant). Use cautiously in hypertension, heart disease, glaucoma, hyperthyroidism, and BPH. Avoid in MAOI use within 14 days. May cause dizziness or sedation. |
| Patient Advice | Do not exceed recommended dose. · Avoid alcohol and other CNS depressants as they increase sedation. · If you have high blood pressure, heart disease, or prostate enlargement, consult doctor before use. · Do not take with MAOIs or within 14 days of stopping them. · May cause drowsiness; avoid driving or operating machinery until you know how it affects you. |