Preformulation characterization and identification of excipients for nevirapine loaded niosomes

Nevirapine (NVP) is used for the management of HIV/AIDS but must be dosed frequently, exhibits unpredictable bioavailability and a side effect profile that includes hepato- and dermo-toxicity. Niosomes are a colloidal drug delivery system that may be used to overcome the low bioavailability, side effect profile and frequent dosing needed when using conventional drug delivery systems. The compatibility of NVP with sorbitan esters, polysorbate, cholesterol and dihexadecyl phosphate (DCP) was investigated using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Fourier Transform Infra-red Spectroscopy (FTIR) and X-ray Powder Diffraction (XRPD). Screening studies were undertaken to identify potential excipients that would produce niosomes with target critical quality attributes (CQA) viz, a particle size (PS) < 1000 nm, a polydispersity index (PDI) < 0.500 and an entrapment efficiency > 90%. The results revealed that sorbitan esters in combination with cholesterol and 5 μmol DCP produced niosomes with the best CQA and Zeta potential (ZP) < -30 mV which suggests good stability of the niosomes on storage. Sorbitan esters produced the smallest niosomes of < 400 nm diameter with a PDI < 0.400 and an entrapment efficiency > 78% without cholesterol. The addition of cholesterol and DCP was essential to form niosomes with target CQA.