Cimetidine is a histamine H2 receptor antagonist that inhibits stomach acid production. It inhibits gastric acid secretion, as well as pepsin and gastrins output. It is available over-the-counter and is mainly used in the treatment of heartburn and peptic ulcers. The development of longer-acting H2 receptor antagonists with fewer drug interactions and adverse effects, such as ranitidine and famotidine, decreased the use of cimetidine, and though it is still used, cimetidine is no longer among the more widely used of the H2-receptor antagonists.
Mechanism of Action of Cimetidine
Cimetidine binds to an H2-receptor located on the basolateral membrane of the gastric parietal cell, blocking histamine effects. This competitive inhibition results in reduced gastric acid secretion and a reduction in gastric volume and acidity.
Indications of Cimetidine
- Gastro-esophageal Reflux Disease
- Hypersecretion gastric
- Cutaneous mastocytosis
- Bronchogenic carcinoma
- Duodenal ulcer prophylaxis
- Erosive esophagitis
- Stomach ulcer
- Upper GI Hemorrhage
- Zollinger-Ellison Syndrome
- Active Duodenal ulcer
- Benign gastric ulcers
- Maintenance therapy Duodenal ulcer
Contra-Indications of Cimetidine
- Clostridium difficile infection
- Inadequate Vitamin B12
- Low amount of magnesium in the blood
- Liver problems
- Interstitial Nephritis
- Subacute cutaneous lupus erythematosus
- Systemic Lupus Erythematosus
- Broken Bone
- Allergies to Proton Pump Inhibitors
Dosage of Cimetidine
Strengths: 100 mg; 200 mg; 300 mg; 400 mg; 800 mg; 900 mg 300 mg/5 mL;
- Parenteral: 300 mg IV or IM every 6 to 8 hours. Alternatively, a continuous IV infusion may be administered at a rate of 37.5 to 50 mg/hour, or up to a maximum rate of 100 mg/hour (2.4 g/day).
- Oral: 800 mg to 1600 mg once a day at bedtime. Alternatively, dosage regimens of 300 mg four times per day, with meals and at bedtime, or 400 mg twice daily, in the morning and at bedtime, have shown to be effective.
- Parenteral: 300 mg IV or IM every 6 hours. Alternatively, a continuous IV infusion may be administered at a rate of 50 mg/hour initially, with 25 mg/hour incremental increases up to a maximum rate of 100 mg/hour (2.4 g/day).
- Oral: 800 mg twice a day, or alternatively, 400 mg four times a day.
- Parenteral: 300 mg IV or IM every 6 hours. Alternatively, a continuous IV infusion may be administered at a rate of 50 mg/hour.
- Parenteral: 300 mg IV or IM every 6 hours. Alternatively, a continuous IV infusion may be administered at a rate of 50 mg/hour initially. Infusion rates have ranged from 40 to 600 mg/hour, but should not exceed a daily total of 2.4 g.
- Oral: 300 mg 4 times a day with meals and at bedtime.
- Parenteral: 300 mg IV or IM every 6 hours. Alternatively, a continuous IV infusion may be administered at a rate of 50 mg/hour. The maximum daily dose should not exceed 2.4 g.
- Oral: 800 mg twice a day, or 400 mg 4 times a day.
Pediatric Gastroesophageal Reflux Disease
- Neonatal: 5 to 10 mg/kg/day administered IV or IM in divided doses every 8 to 12 hours.
- Infants: 10 to 20 mg/kg/day administered IV, IM, or oral in divided doses every 6 to 12 hours.
- Children: 20 to 40 mg/kg/day administered IV, IM, or oral in divided doses every 6 hours.
Side Effects of Cimetidine
The most common
- Nausea and vomiting
- Severe stomach ache
- Severe diarrhea
- Vaginal thrush
- Skin rash
- A headache
- chest pain
- a cough
- diarrhea or loose stools
- difficulty with breathing
- muscle pain
- Abdominal or stomach pain, discomfort, or tenderness
- chills or fever
- difficulty with moving
- a headache, severe and throbbing
- joint or back pain
- muscle aching or cramping
- muscle pains or stiffness
- chest pressure or squeezing pain in the chest
- discomfort in arms, shoulders, neck or upper back
- excessive sweating
- feeling of heaviness, pain, warmth and/or swelling in a leg or in the pelvis
- sudden tingling or coldness in an arm or leg
- sudden slow or difficult speech
- sudden drowsiness or need to sleep
- fast breathing
- sharp pain when taking a deep breath
- fast or slow heartbeat
- coughing up blood
- rust colored urine
- decreased amount of urine
- change in vision
- abnormal or fast heart rate
- weight loss
- chest pain or tightness
- a cough
- arm, back, or jaw pain
- blurred vision
- chest pain or discomfort
- extra heartbeats
- a headache
- mood or mental changes
- muscle pain or cramps
- muscle spasm or jerking of all extremities
Cimetidine may interact with the following drugs, supplements, & may change the efficacy of the drug
- azole antifungal medications (e.g., fluconazole, ketoconazole)
- calcium channel blockers (e.g., diltiazem, nifedipine, verapamil)
- certain benzodiazepines (alprazolam, chlordiazepoxide, clonazepam, diazepam, flurazepam, midazolam, and triazolam)
- glyburide (and other “sulfonylurea” diabetes medications)
- SSRIs (e.g., citalopram, fluoxetine, sertraline)
- theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
- tricyclic antidepressants(e.g., amitriptyline, clomipramine, desipramine, trimipramine)
FDA Pregnancy Category C
The safety of this medication for use during pregnancy has not been established. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
This medication passes into breast milk. If you are a breastfeeding mother and are taking cimetidine, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.