Papers

Improving the stability of potassium clavulanate in admixture with amoxicillin

By Elena M. Vega, BSc, PhD, Ruben H. Manzo, BSc, PhD and Nancy Sola, BSc, PhD

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Elena Vega is a research teaching assistant and Ruben Manzo is a professor in the pharmacy department at the University of Córdoba, Argentina.

At the time the research was started, Nancy Sola was a professor in the pharmacy department at the University of Córdoba

ABSTRACT

OBJECTIVE — To improve the shelf-life of the intravenous solution of amoxicillin and clavulanic acid, by lowering the pH to an extent that does not affect the solubility of amoxicillin.

METHODS — Hydrochloric acid 0.1M was used to lower the pH of intravenous co-amoxiclav. The limit of pH at which the admixture remained clear was determined. The shelf-life (t₉₀) at 25C of both an acidified admixture (pH 7.70–7.80) and a non-modified admixture (Augmentin, pH 9.08–9.19) was determined by direct high performance liquid chromotography measurement of the concentration of the potassium salt of clavulanic acid over 12 hours, in both the presence and absence of light.

RESULTS — Acidified admixture appeared to be more stable (t₉₀ = 12h) than that of non-modified Augmentin (t₉₀ = 5h). Acidified admixture also exhibited lower pH variation over time and retained visual clarity for a longer period.

CONCLUSION — The incorporation of 1ml of sterile 0.1M hydrochloric acid per 10ml of final admixture volume appears to be a good strategy to increase the stability of intravenous co-amoxiclav.

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