TAGAMET HB 200
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TAGAMET HB 200 (TAGAMET HB 200).
Competitive antagonist at histamine H2-receptors, inhibiting gastric acid secretion by blocking histamine-mediated stimulation of parietal cells.
| Metabolism | Hepatic metabolism via cytochrome P450 enzymes (CYP1A2, CYP2C19, CYP2D6, CYP3A4); renal excretion of unchanged drug and metabolites. |
| Excretion | Renal: 75-80% as unchanged drug via glomerular filtration and tubular secretion; biliary/fecal: ~20% as metabolites and unchanged drug. |
| Half-life | Terminal elimination half-life: 2-3 hours in patients with normal renal function. In elderly or renal impairment, half-life may extend to 4-5 hours. |
| Protein binding | Approximately 15-20% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution: 1.0-1.5 L/kg, indicating extensive tissue distribution. Notably penetrates into breast milk and crosses the placenta. |
| Bioavailability | Oral: 60-70% after a 200 mg dose due to first-pass metabolism. Bioavailability is dose-dependent; higher doses may show slightly reduced bioavailability. |
| Onset of Action | Oral: 30-45 minutes for inhibition of gastric acid secretion; peak effect at 1-2 hours. |
| Duration of Action | Duration of acid suppression: 6-8 hours after a single 200 mg oral dose. For antisecretory effect, duration may extend up to 12 hours with higher doses. |
200 mg orally once or twice daily, not to exceed 400 mg per day.
| Dosage form | SUSPENSION |
| Renal impairment | For GFR 10-50 mL/min: reduce dose to 50% or increase dosing interval to every 12 hours. For GFR <10 mL/min: reduce dose to 25% or administer every 18-24 hours. |
| Liver impairment | No specific adjustments for hepatic impairment; use with caution in severe hepatic dysfunction. |
| Pediatric use | Not recommended for use in pediatric patients under 12 years of age. For ages 12-16: 200 mg orally once or twice daily. |
| Geriatric use | Reduce dose based on renal function; consider starting with 200 mg once daily due to age-related decreased renal clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TAGAMET HB 200 (TAGAMET HB 200).
| Breastfeeding | Cimetidine is excreted in human milk with a milk-to-plasma ratio (M/P) of approximately 5.8. Based on typical maternal doses, infant exposure is likely less than therapeutic doses but may cause potential adverse effects. Caution advised; consider alternative H2 antagonists with lower transfer (e.g., famotidine). |
| Teratogenic Risk | Pregnancy Category B. Animal studies have not demonstrated fetal risk, but adequate controlled studies in pregnant women are lacking. No evidence of teratogenicity in humans; however, cimetidine crosses the placenta. Use only if clearly needed. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to cimetidine or any component of the formulation","OTC use in children <12 years without medical supervision"]
| Precautions | ["Avoid use in patients with immune compromise or history of gastric malignancy","May mask symptoms of gastric cancer","Caution in patients with hepatic or renal impairment","Potential for drug interactions due to CYP450 inhibition","Rare adverse effects: confusion, hallucinations (especially elderly), neutropenia, thrombocytopenia, gynecomastia, impotence"] |
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| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for potential adverse effects such as hypotension, bradycardia (if IV administered), and central nervous system effects. In neonates, observe for cimetidine-related effects if maternal use near term. |
| Fertility Effects | Cimetidine has antiandrogenic properties; in males, it can cause gynecomastia, reduced sperm count, and impotence. In females, it may cause galactorrhea or menstrual irregularities due to hyperprolactinemia. Reversible upon discontinuation. |