Effect of different buffered and unbuffered dispersion Medium on the physical and chemical stability of Nystatin suspensions.

Nystatin is a polyene macrolide which is widely used in the treatment of GI fungal infections. Different formulations of the drug including its suspension are available. From the bioavailability point of view, suspensions are usually superior to other dosage forms. The aim of this study was to investigate the influence of type and concentration of cellulosic suspending agents on the physical and chemical stability of nystatin in suspension. To this end, three grades of sodium carboxymethylcellulose (SCMC 358 cps, SCMC 1240 cps, and 1485 cps) as buffered vehicles (pH = 7) and an unbuffered microcrystalline cellulose (Avicel RC 591) vehicle were employed. All the formulations were passed physical stability tests in terms of sedimentation volume, redispersibility and freeze – thaw tests. The formulations were further tested for chemical stability using the Arrhenius method. The test indicated that shelf lives of the buffered suspensions were more or less the same but much higher than that of unbuffered suspension (10 months vs. 1 month).