Evaluation of carboxymethylated plectranthus edulis starch as a suspending agent in metronidazole benzoate suspension formulations.

Some excipients are currently available for the formulation of pharmaceutical suspensions. The objective of this study is to develop cheap and effective starch-based excipient that can be used as an effective alternative for the formulation of pharmaceutical suspensions. Carboxymethylated Plectranthus edulis, Vatke (P. edulis) [fam., Lamiaceae], starch was evaluated as a suspending agent in metronidazole benzoate suspensions in comparison with sodium carboxymethyl cellulose (NaCMC) at a concentration range of 1-4% (w/v). The resulting suspensions were evaluated for their sedimentation volume (%), degree of flocculation, rheology, redispersibility, and dissolution rate. Stability studies were performed for 3 months. The apparent viscosities of the formulations prepared with carboxymethylated P. edulis starch at reaction condition E (CMPS-E) was significantly lower than that of NaCMC (p < 0.05). The flowability of the suspensions, at all concentration levels of the suspending agents, were in the order of CMPS-E > NaCMC. AT 1% concentrations, carboxymethylated P. edulis starch (76 ± 1.5%) provided significantly higher (p < 0.05) sedimentation volume than NaCMC (40 ± 1.5%). At 3% and 4%, both gave comparable sedimentation volume (100%). Potassium dihydrogen phosphate (KH2PO4) employed as a flocculating agent significantly increased (p < 0.05) the sedimentation volume of the suspensions prepared with carboxymethylated P.edulis starch and NaCMC. The redispersibilities of CMPS-E were better than those of NaCMC. All suspensions showed a release of greater than 85% of drug within 1 h. The results of stability studies showed that all suspension formulations were stable. From the foregoing, it can be concluded that carboxymethylated P. edulis starch could be used as an alternative suspending agent.