cimetidine

REMS

Short-term treatment of active duodenal ulcers and benign gastric ulcers.
Maintenance therapy for duodenal ulcers after healing of active ulcer(s).
Management of gastroesophageal reflux disease (GERD).
Treatment of heartburn, acid indigestion, and sour stomach (OTC use).
Management of gastric hypersecretory states (Zollinger-Ellison syndrome).

Unlabeled Use:

Management of GI symptoms associated with the use of NSAIDs.
Management of urticaria.

Action ⬆ ⬇

Inhibits the action of histamine at the H₂-receptor site located primarily in gastric parietal cells, resulting in inhibition of gastric acid secretion.

Therapeutic effects:

Healing and prevention of ulcers.
Decreased symptoms of gastroesophageal reflux.
Decreased secretion of gastric acid.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Enters breast milk and cerebrospinal fluid.

Metabolism/Excretion: 30% metabolized by the liver; remainder is eliminated unchanged by the kidneys.

Half-Life: 2 hr.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO	30 min	45–90 min	4–5 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Lactation: Lactation.

Use Cautiously in:

Renal impairment (more susceptible to adverse CNS reactions; ↑ dose interval recommended if renal impairment is severe);
OB: Safety not established in pregnancy;
Geri: Older adults are more susceptible to adverse CNS reactions (dose recommended).

Adv. Reactions/Side Effects ⬆ ⬇

CV: ARRHYTHMIAS

Endo: gynecomastia

GI: constipation, diarrhea, hepatitis, nausea

GU: ↓sperm count, erectile dysfunction

Hemat: anemia, AGRANULOCYTOSIS, APLASTIC ANEMIA, neutropenia, thrombocytopenia

Neuro: confusion, dizziness, drowsiness, hallucinations, headache

Misc: hypersensitivity reactions

Interactions ⬆ ⬇

Drug-drug:

Cimetidine inhibits drug-metabolizing enzymes in the liver; may lead to ↑ blood levels and toxicity with the following—some benzodiazepines (especially chlordiazepoxide, diazepam, and midazolam), some beta blockers (labetalol, metoprolol, propranolol ),caffeine, calcium channel blockers, carbamazepine, chloroquine, lidocaine, metronidazole, pentoxifylline, phenytoin, propafenone, quinidine, quinine, metformin, sulfonylureas, theophylline, triamterene, tricyclic antidepressants, and warfarin.
May ↑ the effects of succinylcholine, flecainide, procainamide, carmustine, and fluorouracil.
↓absorption of ketoconazole.
Antacids and sucralfate↓ absorption.

Drug-Natural Products:

↑caffeine levels and side effects with caffeine-containing herbs (cola nut, guarana, mate, tea, coffee).

Route/Dosage ⬆ ⬇

PO (Adults ): Short-term treatment of active ulcers: 300 mg 4 times daily or 800 mg at bedtime or 400–600 mg twice daily (not to exceed 2.4 g/day). Duodenal ulcer prophylaxis: 300 mg twice daily or 400 mg at bedtime. GERD: 800–1600 mg/day in divided doses. Gastric hypersecretory conditions: 300–600 mg every 6 hr (up to 12 g/day have been used). OTC use: up to 200 mg may be taken twice daily (for no more than 2 wk).
PO (Children ): Short-term treatment of active ulcers: 20–40 mg/kg/day in 4 divided doses.

Renal Impairment

PO (Adults ): 300 mg every 8–12 hr; further adjustment may be required for concurrent hepatic impairment.
PO (Children ): 10–15 mg/kg/day given in divided doses every 8–12 hr.

Availability ⬆ ⬇

(Generic available)

Tablets: 200 mg^OTC; 300 mg; 400 mg; 800 mg

Assessment ⬆ ⬇

Assess patient for epigastric or abdominal pain and frank or occult blood in the stool, emesis, or gastric aspirate.
Geri: Assess geriatric and debilitated patients routinely for confusion. Report promptly.

Lab Test Considerations:

Monitor CBC with differential periodically during therapy.
- Antagonize effects of pentagastrin and histamine during gastric acid secretion testing. Avoid administration for 24 hr preceding the test.
- May cause false-negative results in skin tests using allergenic extracts. Histamine H antagonists should be discontinued 24 hr prior to the test.
- May cause ↑ serum transaminases and serum creatinine.

Implementation ⬆ ⬇

If antacids or sucralfate are used concurrently for relief of pain, avoid administration of antacids within 30 min–1 hr of cimetidine and take sucralfate 2 hr after cimetidine; may decrease the absorption of cimetidine.
PO: Administer with meals or immediately afterward and at bedtime to prolong effect.
- Doses administered once daily should be administered at bedtime to prolong effect.
- Cimetidine tablets have a characteristic odor.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed for the full course of therapy, even if feeling better. Take missed doses as soon as remembered but not if almost time for next dose. Do not double doses.
- Advise patients taking OTC cimetidine preparations not to take the maximum dose continuously for more than 2 wk without consulting health care professional. Notify health care professional if difficulty swallowing occurs or abdominal pain persists.
- Inform patient that smoking interferes with the action of histamine antagonists. Encourage patient to quit smoking or at least not to smoke after last dose of the day.
- May cause drowsiness or dizziness. Caution patient to avoid driving or other activities requiring alertness until response to the drug is known.
- Advise patient to avoid alcohol, products containing aspirin or NSAIDs, and foods that may cause an increase in GI irritation.
- Inform patient that increased fluid and fiber intake and exercise may minimize constipation.
- Advise patient to report onset of black, tarry stools; fever; sore throat; diarrhea; dizziness; rash; confusion; or hallucinations to health care professional promptly.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

Evaluation/Desired Outcomes ⬆ ⬇

Decrease in abdominal pain, heartburn, acid indigestion, and sour stomach.
Prevention of gastric irritation and bleeding. Healing of duodenal ulcers can be seen by endoscopy. Therapy is continued for at least 6 wk in treatment of ulcers but not usually longer than 8 wk.
Decreased symptoms of esophageal reflux.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇