Formulation effects on the mechanical and release properties of metronidazole suppositories

Abstract

A study of the effects of Tween 20 and Tween 80 non-ionic surfactants, and witepsol H15 and polyethylene glycol (PEG) 2850 bases, on the mechanical and release properties of met ronidazole suppositories was ^nade. Mcchanical strength was assessed by breaking strength values F. The values of F in creased with increase in concentration of surfactant. The val ues of F for formulations containing Tween 20 were higher than those obtained for formulations containing Tween 80. Witepsol bases gave higher values of F than corresponding PEG bases. Release characteristics were assessed by the time for 80% drug release (tg0), values of dissolution rate constants, k, and kj and the time of intersection, t,. The values of t80 decreased while those of k, and 1^ increased with increase in surfactant concen tration. The values of tg0 were lower, while those of k, and k j were higher, for formulations containing Tween 20 than for those formulations containing Tween 80. Witepsol bases gave lower tg0 values and higher k, and 1^ values than their corre sponding PEG bases. The concentration of surfactant, C, had the largest individual effect on the mechanical and release pa rameters while the nature of surfactant, S, had the lowest. The ranking for the individual effects of the variables on F and k, was C>N»S , on tM and k2 was 0»N~S , was on t, was C=N=S.. The interactions between S and C were largest for F, tg0 and le,, and lowest for k, and t,. The ranking of the interaction effects of the variables on F and k2 was S-ON-ON-S , on tg0 was S ON-S—N-C, on k, was N-C>N-S>S-C, and on t, was N-S=N OS-C . The results suggest that the individual and interaction effects of formulation variables would provide useful guides in optimizing metronidazole suppository formulations.