Cimetidine (Tagamet): Uses, Warnings, and Key Facts

What is cimetidine?

Cimetidine is an active ingredient used in medicines for several acid-related conditions. The original content lists use in gastric and duodenal ulcer, symptomatic treatment of gastroesophageal reflux, GERD, Zollinger-Ellison syndrome, and prevention of Mendelson’s syndrome.

The ingredient is listed as cimetidine hydrochloride (HCl).

In the United States, brand names mentioned in the source include Tagamet, Tagamet HB, Leader Heartburn Relief, and Equaline Acid Reducer.

How cimetidine works

Cimetidine antagonizes histamine H2 receptors in the stomach’s parietal cells. In practical terms, this means it helps reduce basal and food-stimulated acid secretion and also reduces pepsin production. The source also describes a cytoprotective effect.

Forms and strengths listed in the source

Therapeutic uses listed in the source

The original content lists cimetidine for the following uses:

• Gastric and duodenal ulcer
• Symptomatic treatment of gastroesophageal reflux
• GERD, including more severe cases
• Prevention of stress ulcer in severe patients at risk of bleeding
• Treatment of bleeding from peptic ulcer or upper gastrointestinal erosions
• Zollinger-Ellison syndrome
• Pancreatic insufficiency, as a complement
• Prevention of Mendelson’s syndrome
• Reduction of malabsorption and fluid loss in short bowel syndrome
• Treatment of NSAID-induced lesions

Dosage information from the source

The source includes detailed dosing by condition, age, and kidney or liver function. Because dosing must be individualized, the safest approach is to use the official product label and clinician guidance for the exact product and indication.

Adults

Examples listed in the source include bedtime dosing, divided daily dosing with meals, and higher-dose regimens for severe conditions such as Zollinger-Ellison syndrome or bleeding-related indications.

Children

The source lists age-based dosing for children 1 to 12 years, infants under 1 year, and neonates, with doses divided every 4 to 6 hours.

Kidney or liver impairment

The original content notes that dose adjustment may be needed in severe liver failure and kidney failure. Exact adjustments depend on the clinical situation and should be checked in the official leaflet or with a healthcare professional.

How to take cimetidine

The source says cimetidine is preferably taken with meals and, in some cases, at bedtime. When used as a complement in pancreatic insufficiency, it should be taken 60 to 90 minutes before meals.

Contraindications

The original content lists:

• Hypersensitivity to cimetidine
• Concomitant use with dofetilide, due to increased risk of ventricular arrhythmias (torsades de pointes)

Warnings and precautions

• Use caution in severe liver failure and kidney failure; dose adjustment may be needed.
• There is limited experience in children; the source says use only when benefit outweighs risk.
• Malignant lesions should be ruled out.
• The source notes an increased risk of community-acquired pneumonia in elderly, immunocompromised, diabetic, or chronic lung disease patients.
• Use caution with coumarins, phenytoin, and theophylline.
• The source reports that cimetidine may worsen arthritis symptoms.
• Mild and reversible confusional states have been described.
• Avoid rapid intravenous injection of less than 5 minutes.

Drug interactions listed in the source

Cimetidine can affect the levels or absorption of several medicines. The original content lists interactions with:

• Tricyclic antidepressants such as amitriptyline
• Class I antiarrhythmics such as lidocaine and quinidine
• Calcium channel blockers such as nifedipine and diltiazem
• Oral sulfonylureas
• Metoprolol and propranolol
• Procainamide
• Metformin
• Cyclosporine and tacrolimus
• Diazepam and chlordiazepoxide
• Atazanavir
• Ketoconazole, itraconazole, and posaconazole
• Carmustine, fluorouracil, epirubicin, and radiotherapy
• Pentobarbital, for parenteral incompatibility

If you take prescription medicines, over-the-counter products, or supplements, check for interactions before using any cimetidine-containing product.

Pregnancy and breastfeeding

The source says there is limited experience in pregnancy and that cimetidine should not be used unless the benefit outweighs the risk.

For breastfeeding, the source states that cimetidine is excreted in breast milk and should not be administered during lactation. It also notes a situation in which, after caesarean section and general anaesthesia, the short half-life may reduce the amount present in milk after sufficient recovery time.

Effects on driving and machinery

No specific effect is expected according to the source. However, if dizziness occurs, do not drive or use dangerous machinery.

Possible side effects listed in the source

• Headache
• Dizziness
• Diarrhea
• Skin rashes
• Myalgia
• Tiredness

What to verify in the official leaflet

If you are reading about a cimetidine product, it is a good idea to confirm the following in the official medication guide or package insert:

• The exact strength and dosage form
• The approved use for that specific product
• Any interaction warnings for your current medicines
• Whether dose changes are needed for kidney or liver problems
• Instructions for pregnancy or breastfeeding

Safety reminder

Frequently asked questions

Sources and references

The original content states that the information was prepared using clinical and molecular data from medicines authorized and marketed in the United States under the Unique Ingredient Identifier (UNII) by the FDA Substance Registration System and the USP.

• FDA Medication Guides
• UNII: 80061L1WGD
• ChemIDplus
• DrugPortal
• PubChem CID: 2756
• NCI Thesaurus: C374