Formulation, characterization, and in vitro evaluation release nimesulide from different rectal suppository bases

Nimesulide is a poorly water-soluble, non-steroidal anti-inflammatory drug for both systemic and topical application. The aim of the study was to assess the influence of the type of base and surfactants (Tween80, Span80, soy lecithin, sodium lauryl sulphate) on drug release from rectal suppositories. Suppositories were prepared in the Unquator® using Cacao butter, Witepsol H15 and PEG1500:PEG400 as a base. The physicochemical properties of the prepared suppositories were in accordance to the Pharmacopoeia’s requirements. In vitro dissolution profile of the formulations was evaluated using USP apparatus 1. It has been shown that most of the nimesulide was released from suppositories prepared on PEG base. Addition of 2% surfactant to lipophilic base suppositories, significantly increased the amount of nimesulide released from all the investigated formulae. Among the formulations containing surfactants, only Witepsol H15 with Span 80 released a nearly complete drug during 210 minutes. The results indicate that the First-Order model is the best fit with the nimesulide in-vitro release from lipophilic suppositories, while the Higuchi model - to the PEG suppositories. The drug release kinetics from suppositories showed that the Cacao butter bases adequately fit data for zero-order kinetics model, while the Higuchi model - for the PEG suppositories.