TAGAMET HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER
Clinical safety rating
safeNo significant drug interactions Can cause hypernatremia and fluid overload.
Competitive antagonist of histamine at the H2 receptor on gastric parietal cells, reducing gastric acid secretion (basal and stimulated).
| Metabolism | Hepatic metabolism via N-oxidation, S-oxidation, and demethylation; major pathway is N-oxidation. CYP450 involvement is minimal; primarily metabolized by flavin-containing monooxygenase (FMO3). |
| Excretion | Renal: 70% unchanged via glomerular filtration and tubular secretion. Biliary/fecal: minor (approximately 10-15% as metabolites). |
| Half-life | Terminal elimination half-life: approximately 2 hours in healthy adults; prolonged in renal impairment (up to 20 hours in anuria). |
| Protein binding | 13-25% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 1.0-2.0 L/kg; large Vd indicates extensive tissue distribution (e.g., muscle, kidney, liver). |
| Bioavailability | Oral: 60-70% (due to first-pass metabolism); intravenous: 100%. |
| Onset of Action | IV infusion: immediate (within minutes) as H2 antagonism begins; oral: 30-60 minutes. |
| Duration of Action | IV infusion: 4-6 hours (gastric acid suppression); oral: 4-6 hours (dose-dependent, up to 8 hours with higher doses). |
| Molecular Weight | 288.8 |
300 mg IV every 6-8 hours, or as a continuous IV infusion of 37.5 mg/hour (900 mg/day) for patients unable to take oral therapy.
| Dosage form | INJECTABLE |
| Renal impairment | For CrCl 30-50 mL/min: 300 mg IV every 8 hours. For CrCl 15-29 mL/min: 300 mg IV every 12 hours. For CrCl <15 mL/min: 300 mg IV every 24 hours. |
| Liver impairment | No specific adjustment for Child-Pugh; use caution and reduce dose in severe hepatic impairment based on clinical response, as clearance may be decreased. |
| Pediatric use | Neonates: 5-10 mg/kg IV every 8-12 hours. Infants and children: 5-10 mg/kg IV every 6-8 hours, not to exceed 300 mg per dose. Adolescents: 300 mg IV every 6-8 hours. |
| Geriatric use | Reduce dose based on renal function; start at lower end of dosing range (e.g., 300 mg IV every 12 hours if CrCl 30-50 mL/min) and titrate to response. Monitor for CNS side effects. |
| 1st trimester | Crosses placenta. No evidence of teratogenicity in human studies; however, use only if clearly needed. |
| 2nd trimester | Crosses placenta. No known fetal harm; use with caution. |
| 3rd trimester | Crosses placenta. No known fetal harm; use with caution, especially near delivery due to potential H2-blocker effects on neonatal gastric acidity. |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Placental transfer | Crosses placenta; fetal serum concentrations approximate maternal levels. |
| Breastfeeding | Cimetidine is excreted into breast milk in concentrations similar to maternal serum. Peak milk levels occur 1-2 hours after dose. May suppress infant gastric acidity and theoretically alter infant microflora. Use with caution; monitor infant for adverse effects. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Cimetidine crosses the placenta. First trimester: Limited data; no increased risk of major malformations in prospective studies. Second/third trimester: No consistent evidence of fetal harm, but cimetidine has been associated with transient neonatal hepatic impairment and antiandrogenic effects in animal studies (dose-dependent). Use only if clearly needed. |
| Fetal Monitoring | Monitor maternal hepatic function, renal function, CBC with differential, and cardiac status (cimetidine may cause bradycardia). In neonate, monitor for signs of histamine H2 antagonist effects: sedation, bradycardia, respiratory depression, hypotonia. Assess infant for potential drug accumulation if maternal renal impairment exists. |
| Fertility Effects | Cimetidine has antiandrogenic properties at high doses (e.g., decreased sperm count, impotence, gynecomastia) in males. In females, high doses may cause galactorrhea. Use may impair fertility, but effects are reversible upon discontinuation. Limited data on direct impact on female fertility. |
■ FDA Black Box Warning
None
| Common Effects | fluid replacement |
| Serious Effects |
Hypersensitivity to cimetidine or any component of the formulation
| Precautions | May cause confusion, hallucinations, or delirium (especially in elderly, renally impaired, or critically ill patients), May cause hepatotoxicity (elevated liver enzymes, hepatitis), May cause bone marrow suppression (neutropenia, agranulocytosis; rare), May cause bradycardia or cardiac arrhythmias with rapid IV administration, May inhibit cytochrome P450 (CYP1A2, CYP2C19, CYP2D6, CYP3A4) leading to increased levels of coadministered drugs (e.g., warfarin, theophylline, phenytoin), May cause gynecomastia or impotence with prolonged high doses, Use with caution in patients with renal impairment (dose adjustment required) |
| Food/Dietary | Cimetidine may increase absorption of alcohol, leading to higher blood alcohol levels. Avoid alcohol. High-fat meals may slightly decrease absorption, but not clinically significant. No specific food restrictions. |
| Clinical Pearls | Cimetidine is a potent inhibitor of CYP1A2, CYP2C19, CYP2D6, and CYP3A4, leading to increased serum levels of many drugs including warfarin, theophylline, phenytoin, and lidocaine. In elderly or renally impaired patients, reduce dose to prevent CNS side effects like confusion or hallucinations. Rapid IV administration can cause hypotension or cardiac arrhythmias; infuse over at least 30 minutes. Monitor for elevated serum creatinine initially due to interference with tubular secretion of creatinine. |
| Patient Advice | Do not smoke while taking this medication, as smoking can decrease its effectiveness. · Avoid alcohol consumption, which can worsen stomach irritation. · Inform your doctor about all medications you take, as cimetidine can interact with many drugs. · Report any confusion, dizziness, or unusual bleeding/bruising immediately. · Take exactly as prescribed; do not increase the dose without consulting your healthcare provider. |
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