What enzyme does cimetidine inhibit?

What enzyme does cimetidine inhibit?

Cimetidine is an inhibitor of microsomal drug metabolism [570,571], and thus one might expect this agent to inhibit hepatic vitamin D 25-hydroxylase, a cytochrome P450-dependent enzyme.

Is cimetidine a P450 inhibitor?

Cimetidine is an inhibitor of hepatic cytochrome P450 (CYP) in vivo and in vitro in both rats and humans. However, the concentrations of cimetidine required to inhibit drug metabolism in hepatic microsomes in vitro are 100-1000-fold higher than those associated with a similar degree of inhibition in vivo.

Is cimetidine a strong CYP inhibitor?

Cimetidine is a weak inhibitor of CYP3A4 and CYP2D6.

Is cimetidine a proton pump inhibitor?

Proton pump inhibitors (PPIs) and histamine-2 receptor blockers (eg, cimetidine) reduce gastric acid production; this slows fat breakdown, which is necessary to complex calcium for gut absorption.

How is cimetidine administered?

Cimetidine comes as a tablet and a liquid to take by mouth. It is usually taken once a day at bedtime or two to four times a day with meals and at bedtime. Over-the-counter cimetidine is usually taken once or twice a day with a glass of water.

What is the mechanism of action for 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.

What is the mechanism of action of cimetidine?

Is cimetidine an H2 blocker?

The H2-receptor antagonist cimetidine competitively blocks histamine from stimulating the H2-receptors located on the gastric parietal cells (these cells are responsible for hydrochloric acid secretion and secretion of the intrinsic factor).

How do you inject cimetidine?

HOW TO USE: Cimetidine is injected into a vein or muscle as directed by your doctor, usually every 6 to 8 hours. When injected into a vein, cimetidine should be given slowly over at least 5 minutes. Giving the medication too fast may cause dizziness, irregular heartbeat, or a drop in blood pressure.

Can cimetidine be given IV?

solution (see Stability of Cimetidine Injection, USP) to a total volume of 20 mL and inject over a period of not less than 5 minutes (see PRECAUTIONS). Intermittent Intravenous Infusion: 300 mg every 6 to 8 hours, infused over 15 to 20 minutes. In some patients it may be necessary to increase dosage.

Which is cytochrome P450 enzyme does cimetidine inhibit?

Cytochrome P450 inhibition. Cimetidine is a potent inhibitor of certain cytochrome P450 (CYP450) enzymes, including CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4. The drug appears to primarily inhibit CYP1A2, CYP2D6, and CYP3A4, of which it is described as a moderate inhibitor.

What kind of interactions are there with cimetidine?

Interactions of potential clinical importance with cimetidine include warfarin, theophylline, phenytoin, carbamazepine, pethidine and other opioid analgesics, tricyclic antidepressants, lidocaine, terfenadine, amiodarone, flecainide, quinidine, fluorouracil, and benzodiazepines.

How does cimetidine reduce absorption of CYP2D6 substrates?

Cimetidine may decrease the effects of CYP2D6 substrates that are prodrugs, such as codeine, tramadol, and tamoxifen. Cimetidine reduces the absorption of ketoconazole and itraconazole (which require a low pH ). Cimetidine has a theoretical but unproven benefit in paracetamol toxicity.

How does cimetidine affect testosterone levels in men?

At typical therapeutic levels, cimetidine has either no effect on or causes small increases in circulating testosterone concentrations in men. Any increases in testosterone levels with cimetidine have been attributed to the loss of negative feedback on the HPG axis that results due to AR antagonism.