HPLC method development for the quantification and stability studies of Amoxcillin and Clavulanic Acid in liquid oral formulations

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Amoxicillin-Clavulanic acid combinations have become first line medicines on the essential medicines list of the National Health Insurance Scheme for the treatment of infections caused by beta-lactamase producing micro-organisms. These organisms have become resistant to amoxicillin. As a result, clavulanic acid which is a beta-lactamase inhibitor is combined with amoxicillin to extend the antibacterial properties of amoxicillin and thus the synergy produced by the two drugs are exploited to treat infections caused by beta-lactamase resistant bacteria. It is essential that the two compounds maintain their stability throughout the period of use to obtain the expected synergy. However, no studies have been conducted on the liquid oral suspension of these drugs under the local Ghanaian temperature storage conditions to ascertain their stability in liquid oral suspension throughout the period of use. Also, few methods that are stability indicative are available for the assay of these liquid oral formulations. To assist in assessing the stability and the quality of these formulations, a simple and cost effective High Performance Liquid Chromatographic (HPLC) method for assay and assessment of stability of the two compounds in liquid oral formulations fixed-dose was developed and validated. The HPLC method employed a C18 reverse phase column Phenomenex, Ultracarb ODS 20micron with an isocratic mixture of methanol, water and sodium acetate buffer pH 4.37 in the ratio of 5:90:5 as the mobile phase. The flow rate was 1ml/min and detection was by means of a UV detector at a wavelength of 220nm. The LOD of amoxicillin and clavulanic acid were 0.00202%w/v and 0.000264%w/v respectively. The LOQ of amoxicillin and clavulanic acid were also 0.00674%w/v and 0.000879%w/v. The method was accurate when compared to a standard method in the British Pharmacopoeia. Five brands of the Amoxicillin-Clavulanic acid combinations in liquid suspensions were analysed. Four out of the five brands passed the assay. Both amoxicillin and Clavulanic acid in reconstituted liquid oral suspensions were not stable under temperatures of 30˚C and 40˚C but were however stable at a temperature of 10˚C in a refrigerator over a period of seven days. However, Clavulanic acid was less stable than V amoxicillin at both temperatures of 30˚C and 40˚C. It was also established that the innovator brand was more stable than the most commonest and highly stocked generic brand on the Ghanaian market.
A Thesis submitted to the Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Science in Pharmaceutical Analysis and Quality Control, 2011