Absolute bioavailability of quinidine in two sustained release preparations

Area of Science:

• Pharmacokinetics
• Drug Delivery Systems

Background:

• Quinidine is an antiarrhythmic drug with a narrow therapeutic index.
• Sustained-release formulations aim to improve patient compliance and reduce dosing frequency.
• Understanding the bioavailability of different sustained-release quinidine preparations is crucial for optimizing therapy.

Purpose of the Study:

• To compare the bioavailability and pharmacokinetic profiles of two novel sustained-release quinidine preparations (A and B).
• To assess the in vivo performance of these formulations against in vitro dissolution data.

Main Methods:

• A pharmacokinetic study involving intravenous administration of quinidine.
• Oral administration of two sustained-release preparations (A and B) in six healthy volunteers (3 females, 3 males).
• Measurement of plasma quinidine concentrations over time to determine absorption rates, peak concentrations, and bioavailability.

Main Results:

• No significant difference in the initial oral absorption rate between preparations A and B.
• Peak plasma quinidine concentration was achieved at 4 hours for both, but was significantly higher for preparation B.
• Preparation A exhibited a slower decline in plasma concentration compared to preparation B.
• Absolute bioavailability was not significantly different between preparation A (median 78.4%) and preparation B (median 87.1%).
• In vivo drug absorption correlated well with in vitro dissolution test results for both preparations.

Conclusions:

• Both sustained-release quinidine preparations demonstrated comparable absolute bioavailability.
• Preparation A's slower decrease in plasma concentration suggests a potentially more favorable pharmacokinetic profile for sustained therapeutic effect.
• The in vitro dissolution data accurately predicted in vivo drug absorption, validating the formulation development process.