Acta Pharm. 63 (2013) 59-69


full paper

Original research paper

Evaluation of degradation kinetics for abamectin in formulations using a stability indicating method


1 School of Pharmacy, The University of Auckland, New Zealand

2 Ancare Scientific Ltd, Auckland, New Zealand

3 School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand

4 School of Pharmacy and Medical Sciences, University of South Australia, Australia

Accepted November 5, 2012


The aim of this study was to evaluate stability characteristics and kinetics behavior of abamectin (ABM) as a 1 % (m/V) topical veterinary solution. During the study, samples stressed at 55 and 70 C were regularly analyzed for several parameters over 8 weeks on a chromatographic (HPLC) system, using a Prodigy C18, 250 4.6 mm, 5 m, column eluting with 15 : 34 : 51 (V/V/V) water/methanol/acetonitrile as mobile phase. The HPLC method was validated for precision, accuracy, linearity and specificity, and was found to be stability indicating. The result showed that degradation of ABM followed first-order kinetics and data on loss in assay rate kobs (s1) and half life (t1/2, days) demonstrated ABM in glycerol formal showing the maximum stability. The degradation behavior of ABM varies from solvent to solvent. The effect of added alkali on pH change and loss in ABM assay was studied and found to be unique for all solvents and very distinct from typical hydrolysis degradation. The present study may serve as a platform to design and develop topical non-aqueous solutions of ABM for veterinary use given there no such comprehensive efforts has been published till date on stability profile of ABM in non-aqueous solvents.


Keywords: abamectin, stability, kinetics, degradation, solvent reactivity