Influence of base on the release of antibiotics from officinal ointments

Abstract

Officinal basis for the antibiotic ointments according to the 4th Yugoslav Pharmacopoeia is a hydrophobic base containing only aliphatic hydrocarbons. The fact that antibiotics are predominantly not lipophylic raises the question about the suitability of that particular type of the base for the manufacturing of antibiotic ointments. Recent studies of the lipid analysis of the skin corneal layer indicated that lipids had shown the bilamellar organization in the skin intercorneal space. Such structural organization could be seen in the ambiphylic bases whose structure was based on carefully selected emulsifier couple, consisting of the lyotropic and thermotropic liquid crystals. The aim of this study was to test the velocity of antibiotics (klindamycin hydrochloride, erythromycin base and chloramphenicol) release from the hydrophobic ointment-type bases, and from ambiphylic bases of anionic and non-ionic types. Membrane-free agar diffusion test as the basic method for testing the release velocity in vitro and Staphylococcus aureus as the strain highly susceptible to the chosen antibiotics were used. All the analyzed samples were manufactured as the suspension-type ointments. The highest growth inhibition zone of the Staphylococcus aureus strain for all three analyzed antibiotics was achieved from the non-ionogenic ambiphylic base; the clear growth inhibition zone area for Staphylococcus aureus strain in the preparations containing anionic ambiphylic base was smaller by 10-31.28%, and in the preparations containing aliphatic hydrocarbon-type base, the decrease was 11.46 - 31.28%, compared to the results achieved with the non-ionogenic ambiphylic base. The optimal release velocity for the analyzed antibiotics was achieved from the non-ionic ambiphylic base.