What is the effect of Cimetidine (Histamine H2-receptor antagonist)?

From the Guidelines

Cimetidine should not be used as a first-line treatment for acid-related disorders due to its potential for drug interactions and the availability of more effective and safer alternatives, such as proton-pump inhibitors 1.

Key Points

• Cimetidine is a histamine H2-receptor antagonist medication used to treat conditions involving excess stomach acid, including peptic ulcers, gastroesophageal reflux disease (GERD), and heartburn.
• The typical dosage for children is 30–40 mg/kg/d, divided in 4 doses, with treatment duration usually 4-8 weeks for ulcers 1.
• Cimetidine works by blocking histamine receptors in the stomach, reducing acid production by inhibiting the action of histamine on parietal cells.
• Common side effects include headache, dizziness, and diarrhea.
• Cimetidine can interact with many medications by inhibiting cytochrome P450 enzymes in the liver, potentially increasing blood levels of drugs like warfarin, phenytoin, and theophylline 1.
• Newer H2 blockers like famotidine have fewer drug interactions, and proton-pump inhibitors are more effective and safer alternatives for acid-related disorders 1.

Considerations

• Cimetidine should be used with caution in patients with kidney or liver impairment, and dosage adjustments may be necessary.
• The potential for tachyphylaxis, which can develop within 6 weeks of initiation of treatment, limiting its potential for long-term use 1.
• Cimetidine has been linked to an increased risk of liver disease and gynecomastia, and these associations may be generalizable to other H2RAs 1.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Cimetidine competitively inhibits the action of histamine at the histamine H2 receptors of the parietal cells and thus is a histamine H2-receptor antagonist. Cimetidine inhibits both daytime and nocturnal basal gastric acid secretion Cimetidine also inhibits gastric acid secretion stimulated by food, histamine, pentagastrin, caffeine and insulin.

Cimetidine is a histamine H2-receptor antagonist that works by competitively inhibiting the action of histamine at the histamine H2 receptors of the parietal cells.

• It inhibits gastric acid secretion stimulated by various factors, including food, histamine, and caffeine.
• The mechanism of action is through competitive inhibition of histamine at the H2 receptors, which reduces gastric acid secretion. 2

From the Research

Cimetidine Overview

• Cimetidine is a histamine2 receptor antagonist used to treat various gastrointestinal conditions, including duodenal ulcers and gastroesophageal reflux 3.
• It has been compared to other dosage regimens in terms of efficacy and safety, with no significant differences in healing rates or adverse reactions observed in some studies 4.

Efficacy of Cimetidine

• A study comparing 400 mg cimetidine twice daily to 1000 mg daily in 50 patients with active duodenal ulceration found healing rates of 72% and 76%, respectively, after 4 weeks 4.
• Cumulative healing rates of 84% and 92%, respectively, were obtained after a further 4 weeks of treatment in patients who remained unhealed 4.
• Cimetidine has been shown to be beneficial in treating gastric and duodenal ulcers, as well as preventing stress ulceration and recurrence of gastric and duodenal ulcer 3.

Safety and Adverse Reactions

• No significant adverse reactions were reported in a study comparing different cimetidine dosage regimens 4.
• Subtle differences exist among histamine2 receptor antagonists, including cimetidine, in terms of drug interactions and adverse effects 3.