Home Drug Guide Cimetidine Hydrochloride

Drug Guide

Generic Name

Cimetidine Hydrochloride

Brand Names Tagamet, Tagamet Hydrochloride In Sodium Chloride 0.9% In Plastic Container

Classification

Therapeutic: H2 receptor antagonist for gastric acid reduction

Pharmacological: Histamine H2 receptor blocker

FDA Approved Indications

Active duodenal ulcer
Active Benign gastric ulcers
GERD (Gastroesophageal reflux disease)
Erosive esophagitis
Zollinger-Ellison syndrome

Mechanism of Action

Cimetidine competitively inhibits histamine at H2 receptors of gastric parietal cells, reducing gastric acid secretion.

Dosage and Administration

Adult: Standard doses range from 200 mg to 400 mg two to four times daily, depending on condition. For Zollinger-Ellison, higher doses may be used under supervision.

Pediatric: Doses vary; typically 20 mg/kg/day divided into 2 doses for children, but should be individualized based on condition.

Geriatric: Start at lower doses due to potential for increased sensitivity and comorbidities.

Renal Impairment: Dose adjustment needed; usually a decrease in dose and/or frequency.

Hepatic Impairment: Use with caution; monitor liver function; no specific dosage adjustment generally required.

Pharmacokinetics

Absorption: Well absorbed orally; bioavailability approximately 60%.

Distribution: Widely distributed, crosses blood-brain barrier and placenta.

Metabolism: Partially metabolized in the liver, undergoes minimal hepatic metabolism.

Excretion: Primarily excreted unchanged via the kidneys.

Half Life: Approximately 1.5 to 4 hours in healthy adults, longer in renal impairment.

Contraindications

Hypersensitivity to cimetidine or other H2 antagonists.

Precautions

Renal or hepatic impairment, including lupus erythematosus, as cimetidine can exacerbate symptoms.

Adverse Reactions - Common

Diarrhea (Common)
Headache (Common)
Dizziness (Common)

Adverse Reactions - Serious

CNS effects (confusion, hallucinations) in elderly or cognitively impaired (Uncommon)
Blood dyscrasias (agranulocytosis, aplastic anemia) (Rare)
Gynecomastia and Galactorrhea in men (Rare)

Drug-Drug Interactions

Cimetidine inhibits cytochrome P450 enzymes, increasing levels of drugs like warfarin, phenytoin, theophylline, caffeine, and benzodiazepines.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for signs of bleeding, renal and hepatic function, CNS effects.

Diagnoses:

Risk for bleeding
Altered mental status in elderly
Impaired gastric mucosal integrity

Implementation: Administer after meals to decrease gastrointestinal irritation, monitor drug levels if applicable.

Evaluation: Assess symptom relief of ulcers or GERD, monitor for adverse effects.

Patient/Family Teaching

Take medication as prescribed.
Report signs of mental status changes or bleeding.
Avoid smoking and alcohol, which can exacerbate gastric issues.

Special Considerations

Black Box Warnings:

Cimetidine has no current black box warnings.

Genetic Factors: Limited data on genetic influence.

Lab Test Interference: May interfere with thyroid function tests and drug serum levels.

Overdose Management

Signs/Symptoms: Confusion, hallucinations, slurred speech, hypotension, dizziness.

Treatment: Supportive care, activated charcoal if recent ingestion, and monitoring. Hemodialysis can be considered in severe cases, especially in renal failure.

Storage and Handling

Storage: Store at room temperature, protected from light and moisture.

Stability: Stable for up to 2-3 years when stored properly.