Gender differences in ondansetron pharmacokinetics in rats

Area of Science:

• Pharmacology
• Drug Metabolism
• Pharmacokinetics

Background:

• Ondansetron metabolism primarily involves hepatic CYP2D and 3A1/2 enzymes in male Sprague-Dawley rats.
• CYP2D1 and CYP3A2 are male-dominant and male-specific isozymes in rats, respectively.
• Differences in these enzymes suggest potential gender-based pharmacokinetic variations for ondansetron.

Purpose of the Study:

• To investigate and compare the pharmacokinetics of ondansetron in male and female Sprague-Dawley rats.
• To evaluate gender-specific differences in ondansetron absorption, distribution, metabolism, and excretion (ADME) following intravenous and oral administration.

Main Methods:

• Intravenous and oral administration of ondansetron (8 mg/kg) to male and female Sprague-Dawley rats.
• Analysis of pharmacokinetic parameters including Area Under the Curve (AUC) and non-renal clearance (Clnr).

Main Results:

• Following intravenous administration, male rats exhibited a significantly smaller AUC (22.6% decrease) and faster time-averaged non-renal clearance (27.3% increase) compared to females.
• Oral administration resulted in a significantly smaller AUC in male rats (58.8% decrease) versus female rats.
• Faster hepatic blood flow in males may contribute to IV results; increased intestinal and hepatic metabolism likely explains oral results.

Conclusions:

• Significant gender-dependent differences in ondansetron pharmacokinetics exist in Sprague-Dawley rats.
• Male rats demonstrate altered ondansetron disposition, characterized by reduced systemic exposure and faster clearance, attributed to metabolic and potential blood flow variations.