TAGAMET HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER
Clinical safety rating: safe
No 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). |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Breastfeeding | Cimetidine is excreted into human breast milk (M/P ratio approximately 0.7). Peak milk levels occur 1-2 hours after dose. Milk levels are ~10-20% of maternal serum levels. Dose equivalent to infant is about 6-10% of maternal weight-adjusted dose. Caution: potential for anticholinergic effects in the infant. Monitor infant for drowsiness, bradycardia, or hypotonia. Alternative agents (e.g., ranitidine) are preferred. |
| Teratogenic Risk |
■ FDA Black Box Warning
None
| Common Effects | fluid replacement |
| Serious Effects |
["Hypersensitivity to cimetidine or any component of the formulation","Use in patients with porphyria (may precipitate acute attacks)","May interfere with vitamin B12 absorption (long-term use associated with deficiency)"]
| 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)"] |
Loading safety data…
| 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. |