Background: Benzylpenicillin is water soluble natural penicillin used only by parenteral administration. Fast decomposition in acidic environment is the reason why benzylpenicillin can not be orally used. Phenoxymethylpenicillin is natural penicillin used in therapy by oral administration (filmed tablets, tablets, syrup, and suspension). It is relatively stable in acidic environment and has a bioavailability of about 50%.
Objective: The purpose of this study was to increase the stability of these penicillins in acidic environment (pH = 1.2) by using auxiliary substances: β-cyclodextrin, 2-hydroxypropil-β-cyclodextrin, magnesium glutamate and magnesium aspartate.
Methods: Improvements of stability were measured by high performance liquid chromatography in the absence and presence of the mentioned auxiliary substances.
Results: Cyclodextrins significantly improved the stability of the studied penicillins in acidic environment. Glutamate and aspartate showed no effect on this regard.
Conclusions: Significant improvement of benzylpenicillin and phenoxymethylpenicillin stability and possible pharmacokinetics can be achieved by using cyclodextrins.