Hepatic encephalopathy and altered cimetidine kinetics

Area of Science:

• Pharmacology
• Hepatology
• Clinical Pharmacy

Background:

• Liver cirrhosis significantly alters drug pharmacokinetics.
• Portal systemic encephalopathy (PSE) is a common complication of cirrhosis.
• Cimetidine is a widely used H2 receptor antagonist.

Purpose of the Study:

• To investigate cimetidine pharmacokinetics in cirrhotic patients with and without a history of portal systemic encephalopathy (PSE).
• To compare cimetidine metabolism and clearance between these patient groups and healthy subjects.

Main Methods:

• Single intravenous 300-mg dose of cimetidine administered to 16 cirrhotic patients.
• Patients categorized based on history of portal systemic encephalopathy (PSE).
• Pharmacokinetic parameters including volume of distribution, biologic half-life (t 1/2), and clearance were analyzed.

Main Results:

• No significant differences in volume of distribution, biologic t 1/2, or distributional clearance were observed between groups.
• Cirrhotic patients with a history of PSE exhibited significantly lower total body clearance of cimetidine compared to those without PSE and healthy controls.
• Reduced formation of cimetidine sulfoxide was noted in patients with a history of PSE, indicated by lower area under the concentration-time curve (AUC).

Conclusions:

• Cirrhotic patients with a history of PSE demonstrate impaired cimetidine total body clearance.
• A 40% reduction in cimetidine clearance necessitates dosage reduction in cirrhotic patients with PSE history to mitigate central nervous system (CNS) side effects.
• These findings highlight the importance of individualized dosing strategies in cirrhotic patients with neurological complications.