Bioavailability of hydrochlorothiazide from tablets and suspensions

Area of Science:

• Pharmacokinetics
• Drug Metabolism and Disposition

Background:

• Hydrochlorothiazide is a widely prescribed diuretic.
• Understanding its dose-proportionality is crucial for optimizing therapeutic use.

Purpose of the Study:

• To determine the bioavailability of hydrochlorothiazide after single oral doses.
• To assess dose proportionality of hydrochlorothiazide pharmacokinetics.

Main Methods:

• 12 healthy male volunteers received single oral doses (25-200 mg) of hydrochlorothiazide tablets and suspension.
• Plasma and urine hydrochlorothiazide levels were quantified using High-Performance Liquid Chromatography (HPLC).

Main Results:

• Hydrochlorothiazide plasma levels were described by a triexponential function.
• Peak plasma concentrations (Cmax) and area under the plasma concentration-time curve (AUC0-36) were dose-proportional.
• Urinary recovery of unchanged hydrochlorothiazide (50-63%) was consistent across doses.
• No significant differences in electrolyte excretion were observed.

Conclusions:

• Hydrochlorothiazide exhibits dose-proportional bioavailability within the therapeutic dose range.
• This predictable pharmacokinetic profile supports consistent therapeutic outcomes.