Absorption profiles of rectally administered midazolam estimated by deconvolution.

Area of Science:

• Pharmacokinetics
• Drug Absorption
• Pharmacology

Background:

• Rectal administration of midazolam is a common route for sedation.
• Understanding the absorption kinetics is crucial for optimizing drug efficacy and safety.

Purpose of the Study:

• To evaluate the utility of an algebraic deconvolution procedure for estimating rectal midazolam absorption profiles.
• To compare deconvolution results with conventional AUC methods using reduced sampling periods.

Main Methods:

• An algebraic deconvolution procedure was applied to plasma concentration-time data of rectally administered midazolam (0.3 mg/kg) in 8 healthy subjects.
• Data from reduced sampling periods (120 min and 300 min) were analyzed and compared to results from the full sampling period (840 min).
• Bioavailability was assessed using both AUC ratio and deconvolution methods.

Main Results:

• Deconvolution analysis using data up to 120 min yielded a bioavailability of 0.46 +/- 22% (p = 0.02) compared to AUC ratio (0.52 +/- 16%).
• Using data up to 300 min, deconvolution resulted in a bioavailability of 0.51 +/- 20% (p = 0.6), closely matching the AUC method.
• Absorption was found to be nearly complete within 120 min, with 40% of the dose absorbed after 60 min.

Conclusions:

• Rectal absorption of midazolam can be adequately characterized using deconvolution with approximately 5-hour sampling.
• The deconvolution algorithm is user-friendly, especially when utilizing polyexponential parameters from curve fitting.
• This approach allows for efficient pharmacokinetic data acquisition, potentially reducing study duration and subject burden.