Grapefruit juice increases the bioavailability of artemether

Area of Science:

• Pharmacology
• Drug Metabolism
• Clinical Pharmacokinetics

Background:

• Artemether is an antimalarial drug requiring understanding of its metabolic pathways.
• Interactions between food/beverages and drug pharmacokinetics can significantly alter drug efficacy and safety.
• Grapefruit juice is a known inhibitor of cytochrome P450 enzymes, particularly CYP3A4.

Purpose of the Study:

• To investigate the pharmacokinetic impact of grapefruit juice on artemether absorption and elimination.
• To assess potential electrocardiographic changes, specifically bradycardia and QTc prolongation, associated with altered artemether concentrations.

Main Methods:

• A pharmacokinetic study involving six healthy male subjects receiving artemether with water or grapefruit juice.
• Collection of plasma and saliva samples, along with electrocardiogram recordings over 8 hours post-dose.
• Quantification of artemether and its metabolite dihydroartemisinin using high-performance liquid chromatography; pharmacokinetic parameters derived from a one-compartment model.

Main Results:

• Grapefruit juice more than doubled artemether's peak concentration (Cmax) and area under the curve (AUC), indicating increased bioavailability.
• The time to reach peak concentration (tmax) was significantly reduced with grapefruit juice.
• No significant changes in artemether's elimination half-life or dihydroartemisinin kinetics were observed; no electrocardiographic abnormalities were detected.

Conclusions:

• Grapefruit juice substantially enhances artemether oral bioavailability, likely via inhibition of intestinal CYP3A4-mediated presystemic metabolism.
• The observed pharmacokinetic changes did not lead to adverse electrocardiographic effects in healthy subjects.
• Findings highlight the importance of considering food-drug interactions for artemether dosing.