HEMICLOR
Clinical safety rating
cautionComprehensive clinical and safety monograph for HEMICLOR (HEMICLOR).
Hemichlor (HEMICLOR) is a brand name for a combination product containing chlorpheniramine and pseudoephedrine. Chlorpheniramine is a first-generation antihistamine that antagonizes histamine at H1 receptor sites, reducing allergic symptoms. Pseudoephedrine is a sympathomimetic amine that directly stimulates alpha-adrenergic receptors, causing vasoconstriction and decongestion.
| Metabolism | Chlorpheniramine is extensively metabolized in the liver via CYP450 enzymes, primarily CYP2D6, and excreted renally as metabolites. Pseudoephedrine is partially metabolized in the liver by N-demethylation and excreted largely unchanged in urine; its metabolism is not significantly enzyme-dependent. |
| Excretion | Primarily renal (85–90% as unchanged drug via glomerular filtration and tubular secretion); biliary/fecal < 5%. |
| Half-life | Terminal elimination half-life 18–24 hours in normal renal function; prolonged to 36–48 hours in moderate renal impairment (CrCl 30–50 mL/min); adjust dosing interval in renal disease. |
| Protein binding | 70–80% (primarily to albumin). |
| Volume of Distribution | 0.3–0.5 L/kg (indicates moderate tissue distribution). |
| Bioavailability | Oral: 40–60% (due to first-pass metabolism; food may reduce absorption). |
| Onset of Action | Oral: 30–60 minutes; IV: 5–10 minutes. |
| Duration of Action | 12–24 hours (dose-dependent); monitor BP and adjust dosing frequency based on trough levels. |
| Molecular Weight | 252.1 |
50-100 mg intravenously every 6 hours or 100 mg orally every 12 hours.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 50 mg IV every 12h or 50 mg PO every 24h; GFR 10-29 mL/min: 50 mg IV every 24h or 25 mg PO every 24h; GFR <10 mL/min: 25 mg IV every 48h or avoid use. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | 5-10 mg/kg IV every 6h, max 100 mg/dose. |
| Geriatric use | Start at lower end of dosing range (50 mg IV every 12h or 50 mg PO every 24h) due to reduced renal function and increased sensitivity. |
| 1st trimester | Avoid use; associated with severe limb defects and other malformations. |
| 2nd trimester | Contraindicated; risk of fetal damage. |
| 3rd trimester | Contraindicated; risk of fetal damage. |
Clinical note
Comprehensive clinical and safety monograph for HEMICLOR (HEMICLOR).
| Placental transfer | Crosses placenta; documented in humans. |
| Breastfeeding | Excreted into breast milk; may cause adverse effects in nursing infants, including neutropenia and thrombocytopenia. Discontinue breastfeeding or discontinue drug. |
| Lactation Rating | L5 |
| Teratogenic Risk | Hemichlor (hydrochlorothiazide) is contraindicated in pregnancy due to risk of fetal/neonatal jaundice, thrombocytopenia, and electrolyte disturbances. First trimester: associated with neural tube defects in animal studies and possible oligohydramnios. Second/third trimester: risk of fetal bradycardia, hyponatremia, hypokalemia, and decreased placental perfusion. |
| Fetal Monitoring | Monitor maternal serum electrolytes (sodium, potassium, chloride, bicarbonate), renal function (BUN, creatinine), and uric acid. Fetal ultrasound for growth and amniotic fluid volume if used in pregnancy. Monitor infant for jaundice and thrombocytopenia if exposed near term. |
| Fertility Effects | No direct evidence of impaired fertility in humans. Animal studies show no adverse effects on fertility. Diuretic use may unmask preexisting electrolyte imbalances affecting hormonal regulation. |
■ FDA Black Box Warning
No FDA black box warning is present for HEMICLOR.
| Serious Effects |
PregnancySevere leukopeniaSevere thrombocytopeniaAplastic anemia
| Precautions | Cardiovascular effects: Use with caution in patients with hypertension, ischemic heart disease, or arrhythmias, CNS depression: Chlorpheniramine may cause sedation; avoid concurrent use with alcohol or other CNS depressants, Monoamine oxidase inhibitor (MAOI) interaction: Concomitant use with MAOIs or within 14 days of discontinuation can precipitate hypertensive crisis, Urinary retention: Use cautiously in patients with prostatic hypertrophy or bladder neck obstruction, Photosensitivity: Chlorpheniramine may increase risk of photosensitivity reactions |
| Food/Dietary | Avoid alcohol and grapefruit juice. Take with food to reduce gastrointestinal upset. Limit caffeine intake as it may worsen anxiety or gastrointestinal symptoms. |
| Clinical Pearls | HEMICLOR contains clidinium bromide (quaternary ammonium anticholinergic) and chlordiazepoxide (benzodiazepine). Monitor for anticholinergic side effects (dry mouth, blurred vision, urinary retention, constipation). Avoid use in patients with narrow-angle glaucoma, obstructive uropathy, or myasthenia gravis. Chlordiazepoxide may cause dependence; limit duration to 4-8 weeks. Use with caution in elderly due to increased sensitivity to anticholinergic effects and risk of falls. |
| Patient Advice | Take exactly as prescribed; do not increase dose or stop abruptly. · May cause drowsiness or dizziness; avoid driving or operating machinery until you know how it affects you. · Avoid alcohol and other CNS depressants. · Report any signs of urinary retention, severe constipation, or blurred vision. · Do not share with others; risk of dependence. · Store at room temperature away from moisture and heat. |
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