The main effect of cimetidine is to inhibit gastric acid secretion, which can be used to relieve symptoms such as stomach pain, heartburn sensation (heartburn), and acid reflux caused by excess stomach acid. Cimetidine is an H2 receptor blocker, which can inhibit gastric acid secretion, and can significantly inhibit diurnal basal gastric acid secretion, and can also inhibit gastric acid secretion induced by food, histamine, pentagastrin, caffeine and insulin. In clinical practice, it is mainly used to relieve stomach pain, heartburn (heartburn), acid reflux and other symptoms caused by excessive stomach acid. Cimetidine may cause adverse reactions such as gynecomastia, lactation, decreased libido, diarrhea, dizziness or headache, muscle cramps or myalgia, rash, and hair loss when taken. It should be used with caution in patients with severe cardiac and respiratory disorders, systemic lupus erythematosus, organic encephalopathy, and hepatic or renal impairment, and should be contraindicated in pregnant and lactating women, and in those who are allergic to the product. Cimetidine is generally not recommended for concomitant use with aluminum hydroxide, magnesium oxide, nitrazepam, diazepam, theophylline, propranolol, aspirin and gentamicin. It is recommended that cimetidine be used in advance to consult a doctor, strictly in accordance with medical advice, not self-medication, so as not to delay or even aggravate the condition.