Disposition of aprophen in rats

Area of Science:

• Pharmacology
• Drug Metabolism
• Toxicology

Background:

• Apropfen is an anticholinergic agent.
• Understanding its pharmacokinetic profile is crucial for its therapeutic application.

Purpose of the Study:

• To investigate the pharmacokinetics and distribution of [14C]aprophen in rats.
• To identify the active form of aprophen responsible for its pharmacological effects.

Main Methods:

• Intravenous administration of [14C]aprophen to rats.
• Measurement of drug concentrations in plasma and tissues over time.
• In-vitro hydrolysis and receptor binding assays.

Main Results:

• Rapid distribution of aprophen to highly perfused organs (t1/2 alpha = 4 min).
• Apparent elimination phase with a t1/2 beta of 23.5 min.
• Hydrolysis to diphenylpropionic acid and diethylaminoethanol; only diethylaminoethanol showed muscarinic receptor binding.
• Unchanged aprophen demonstrated higher plasma concentrations and binding activity than its metabolites.

Conclusions:

• Apropfen exhibits rapid distribution and a high metabolic rate in rats.
• Unchanged aprophen is the primary contributor to the drug's in-vivo actions.
• Diethylaminoethanol, a metabolite, competes with muscarinic receptors but at lower concentrations.