Rectal bioavailability of ibuprofen from hard gelatin capsules containing sodium phosphates as adjuvants and soft gelatin capsules or suppositories as references

The rectal bioavailability of ibuprofen can be affected by including differ ent diluents in hard gelatin capsules. In the present study, sodium phospha tes were used as additives in order to increase the dissolution rate of an acidic drug, ibuprofen, in the rectum. The results showed shortened-times,l es at the beginning of drug absorption, while thereafter the t(max) and mea n residence time decreased. In addition, adjusting the levels of sodium pho sphates increased the C-max value. The addition of phosphates had no marked effect on the degree of bioavailability of ibuprofen. The effect of the nu mber of capsules on the I-ectal bioavailability of ibuprofen was also studi ed. When the single 400 mg dose of ibuprofen was administered in two, 200 m g capsules (size 1), bioavailability was about 25% higher than? that achiev ed with one, 400 mg capsule. The hypothesis was that the first unit was pus hed deeper into the rectum by the other capsule, thus increasing the absorp tion area. On the other hand rectal drug administration was more agreeable if only one unit was used Precoating the capsules with hard fat facilitated administration, thus increasing compliance. Finally during this study, the rectal bioavailability of ibuprofen from hard gelatin capsules containing sodium phosphates (30 mg) was compared with a commercial soft gelatin capsu le and a suppository. which were used as reference products. The conclusion was that a hard gelatin capsule is almost bioequivalent to the suppository and may be slightly more effective than the soft gelatin capsule. Thus the hard gelatin capsule is a noteworthy dosage form for rectal use in some sp ecial cases such as drug therapy for seriously ill patients.