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Bioavailability of allopurinol oral and rectal dosage forms
American Journal of Hospital Pharmacy
|March 1, 1981
Summary
Rectal allopurinol suppositories showed very low bioavailability, with cocoa butter bases yielding minimal drug levels and polyethylene glycol bases resulting in undetectable amounts. This route is not efficient for allopurinol administration.
Area of Science:
- Pharmacokinetics
- Drug Delivery Systems
Background:
- Allopurinol is a common medication for gout and hyperuricemia.
- Evaluating alternative drug delivery routes is crucial for patient compliance and therapeutic efficacy.
Purpose of the Study:
- To assess the bioavailability of allopurinol administered rectally via suppositories compared to oral tablets.
- To investigate the impact of different suppository bases (cocoa butter and polyethylene glycol) on allopurinol absorption.
Main Methods:
- A randomized, three-way crossover study involving five healthy volunteers.
- Administration of 300 mg allopurinol orally (tablets) and rectally (suppositories).
- Serial blood sampling for 72 hours, analyzed by high-performance liquid chromatography for allopurinol and oxipurinol.
Main Results:
- Oral allopurinol peaked at 1.5 ± 0.23 µg/mL at 5.20 ± 0.65 hours.
- Cocoa butter suppositories resulted in undetectable allopurinol and a low oxipurinol peak (0.34 ± 0.14 µg/mL), with 5.77 ± 2.5% bioavailability.
- Polyethylene glycol suppositories showed no detectable allopurinol or oxipurinol levels.
Conclusions:
- Rectal administration of allopurinol using either cocoa butter or polyethylene glycol suppositories is not an effective drug delivery method.
- The polyethylene glycol base may interact with allopurinol, hindering absorption, as suggested by in vitro dialysis studies.