Chapter 50, Problem 7NERQ

Summary Introduction

To define:

Administration of cimetidine is 300 mg in 100 mL normal saline IVPB tid. The infusion should be completed over 30 minutes. If the infusion pump is programmed to deliver to the drug over 30 minutes, find the amount of mL/hour of cimetidine for each IVPB dose that is programmed by the nurse.

Concept introduction:

H₂ receptor antagonists such as cimetidine, famotidine, ranitidine, and nizatidine are used to treat gastroesophageal reflux disease (GERO), peptic ulcer, and erosive esophagitis. Also, they are used as adjunct therapy for gastrointestinal tract bleeding. Cimetidine is the first prototypical H₂ receptor antagonist released on the market. Cimetidine or other H₂ receptor antagonists block the effect of histamine receptors, which are found in the parietal cells. These cells secrete hydrochloric acid (HCl) in the stomach. However, oversecretion of HCl may cause various gastrointestinal problems. The inhibition of histamine receptors by H₂ receptor antagonists results in a reduced response of parietal cells to stimuli. This, in turn, leads to a decreased acid secretion. About 90% of acid secretion can be suppressed by H₂ receptor antagonists.

Cimetidine has more risk in the case of drug interactions than other H₂ receptor antagonists. Cimetidine can bind to enzymes of the liver cytochrome P-450, which is mainly involved in the metabolisms of several drugs (for example, phenytoin).