Abstract
In order to investigate the process of percutaneous absorption from various ointment bases, the blood levels of piroxicam were determined at optimal intervals after the ointment application in rabbits. After the oral and intravenous administrations, the plasma levels of piroxicam were described by the two-compartment model. A pharmacokinetic model similar to the percutaneous absorption of indomethacin was developed to test the concepts regarding the percutaneous absorption of piroxicam from topical ointment bases. A reasonably good fit between experimental and calculated values was obtained by taking into account identical absorption rate constant (K a) and the changes in drug release constant (K r) and the fraction of drug absorbed (F). We found that piroxicam in the o/w ointment base (UCH ointment containing 12% propylene glycol) had a better percutaneous absorption effect than the other three different kinds of ointment bases which were a simple ointment, PEG ointment and petrolatum rosewater ointment. The pH value of the water phase in UCH ointment containing 12% propylene glycol was adjusted to pH 9.2 by the sodium bicarbonate-buffered solution, then the percutaneous absorption of piroxicam could be increased. The effect of the amount of piroxicam on the percutaneous absorption was also investigated. The optimal effect with the additives in the ointment was finally attained with an addition of 5% urea.
Published Version
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