Pentobarbital absorption from capsules and suppositories in humans

Area of Science:

• Pharmacokinetics
• Drug Delivery Systems

Background:

• Pentobarbital is a barbiturate with various clinical applications.
• Understanding the bioavailability and absorption kinetics of different dosage forms is crucial for optimizing therapeutic outcomes.

Purpose of the Study:

• To compare the serum pentobarbital levels and pharmacokinetic profiles of an oral capsule versus two rectal suppository formulations.
• To determine the absorption rates and bioavailability of pentobarbital from these distinct dosage forms.

Main Methods:

• Serum pentobarbital levels were measured after oral and rectal administration.
• Pharmacokinetic constants from previous intravenous studies were utilized.
• In vitro drug release studies were conducted for the suppository formulations.

Main Results:

• All three dosage forms demonstrated 100% absorption.
• Peak serum pentobarbital levels were achieved at 1 hour (capsule), 4 hours (Suppository A), and 10 hours (Suppository B).
• In vitro release rates correlated with in vivo absorption, with Suppository A releasing drug faster than Suppository B.

Conclusions:

• Oral capsules and Suppository A exhibited first-order absorption kinetics.
• Suppository B displayed a complex absorption pattern, requiring a sequential zero-order and first-order model.
• Rectal administration of pentobarbital results in significantly delayed peak serum concentrations compared to oral administration.