Pharmacokinetics of dipyridamole

Area of Science:

• Pharmacology
• Clinical Pharmacology
• Drug Metabolism

Background:

• Dipyridamole, initially a coronary vasodilator, is now explored for thromboembolic diseases due to its platelet function inhibition.
• Hepatic biotransformation to monoglucuronide leads to biliary/fecal excretion, with minor renal excretion.
• Enterohepatic circulation influences dipyridamole's elimination pathway.

Purpose of the Study:

• To characterize the pharmacokinetics of dipyridamole following intravenous and oral administration in humans.
• To determine key pharmacokinetic parameters including disposition and absorption rates, and biological half-life.
• To assess the systemic availability of oral dipyridamole formulations.

Main Methods:

• Intravenous and oral administration of dipyridamole to four healthy human volunteers.
• Analysis of serum concentration-time data using an open two-compartment pharmacokinetic model for IV administration.
• Application of a pharmacokinetic model with consecutive first-order input steps for oral administration to evaluate dissolution and absorption.

Main Results:

• Intravenous dipyridamole disposition fits an open two-compartment model with linear kinetics.
• Oral dipyridamole absorption and disposition modeled by consecutive first-order processes.
• Biological half-lives ranged from 84–145 minutes (disposition rate constants: 0.0051–0.0083 min⁻¹).
• Oral absorption rate constant was approximately 0.07 min⁻¹.
• Systemic availability of 100 mg oral dipyridamole tablets varied between 37% and 66%.

Conclusions:

• Dipyridamole exhibits predictable pharmacokinetic behavior after IV and oral administration in humans.
• The study provides crucial data on dipyridamole's absorption, disposition, and bioavailability, essential for optimizing its therapeutic use.
• Understanding dipyridamole pharmacokinetics aids in its application for thromboembolic disease treatment and platelet function modulation.