Pharmacological action of cimetidine is complicated. It mainly inhibit the activity of hepatic drug metabolizing enzymes and reduce hepatic blood flow. When used in combination with other drugs that are mainly metabolized and inactivated by the liver, the metabolism and clearance of these drugs can be slowed down, and the blood drug concentration can be increased. Be careful about the drug interaction if taking cimetidine tablets or cimetidine injection. Now we introduce the interaction of cimetidine with other drugs beiefly.
- Aluminum hydroxide, magnesium oxide or metoclopramide injection or tablet can reduce the blood concentration of cimetidine.
- Cimetidine may reduce the efficacy of sucralfate.
- As a liver drug enzyme inhibitor. Cimetidine can increase the serum concentration and slow down the heart rate if used with propranolol. When combined with phenytoin or other hydantoins, cimetidne may increase the latter’s blood concentration, resulting in phenytoin poisoning.
- The combination of cimetidine and opioids can cause adverse reactions such as respiratory depression and mental confusion in patients with chronic renal failure.
- Cimetidine can increase the absolute availability of verapamil, which might lead to rare but serious side effects.
- The combination of cimetidine and benzodiazepines may increase the blood concentration of diazepam, aggravate sedation and other central nervous system depression symptoms, and may develop respiratory and circulatory failure.
- Do not take cimetidine with digoxin and quinidine as cimetidine can inhibit the metabolism and increase the plasma concentrations of digoxin and quinidine.
- Cimetidine can delay the metabolism of caffeine and lead to toxic reactions.
- It can reduce the excretion rate if combine cimetidine with warfarin anticoagulants, leading to bleeding tendency.
- The combination of cimetidine and captopril may cause psychotic symptoms.
- When combined with aminoglycoside antibiotics, it may cause respiratory depression or respiratory arrest as cimetidine has a similar muscle-nerve blocking effect to aminoglycosides.
