In vitro interaction of Amoxicillin with Calcium Chloride (Fused) at pH 2.4 and pH 7.4

Article history: This study was aimed to evaluate the in vitro complexation nature and strength of complex which may be formed due to interaction between Amoxicillin and Calcium chloride (CaCl2). The interaction of Amoxicillin and Calcium chloride (fused) has been studied in aqueous systems at a fixed temperature (37 ± 0.5) °C and under different pH (pH 2.4 and pH 7.4) by using some physical methods as spectral observation, Job's method of continuous variation, Ardon's method. From spectrophotometric study, Amoxicillin gives a sharp peak at 272 nm when Calcium chloride mixed with Amoxicillin in 1:1 ratio the intensity of the peak of Amoxicillin change remarkably due to interaction. The jobs plot was obtained by plotting absorbance difference against the mole fraction of the each drug at pH 2.4 and pH 7.4. Amoxicillin forms strong 1:1 complex with Calcium chloride and reverse V Shaped curves indicate the formation of 1:1 complexes of Amoxicillin with Calcium chloride. These may indicate strong kinetics of complexation between Amoxicillin with Calcium chloride. The value of stability constant for the complexation of Amoxicillin with calcium chloride at pH 2.4 and pH 7.4 were obtained from the spectral data using Ardon's plot. The value of stability constant for the drug-metal system at pH 2.4 and pH 7.4 are 5.54 and 6.67 respectively. At pH 2.4 it is found that Amoxicillin form relatively stable complex with Calcium chloride (stability constant 6.67) is high in comparison to pH 7.4. It can therefore be concluded that a careful consideration is needed during concurrent administration of Amoxicillin with Calcium chloride.