In this work, two methods are described for the simultaneous determination of clopidogrel bisulfate with HMG Co-A reductase inhibitors/statins. The first method comprised of quantitative determinations of clopidogrel bisulfate in presence of HMG Co-A reductase inhibitors (atorvastatin, pravastatin simvastatin and rosuvastatin) in buffers of pH 1, 4 (simulating gastric environments), pH 7.4 (simulating blood pH) and pH 9 (simulating intestinal pH) at body temperature (37ºC) using UV/VIS spectrophotometer. Derivative spectroscopy coupled with zero-crossing measurements was used for separating the interfering wavelengths of clopidogrel and statins. Least square regression analysis was performed to measure the concentrations of these drugs. It was observed that clopidogrel interacted with statins at all four pH, especially in simulated gastric environments. In the second case, reversed phase liquid chromatographic (RP-LC) method was developed for simultaneous determination and to investigate the interactions between clopidogrel and HMG Co-A reductase inhibitors. These interactions were evaluated by RP-LC in buffers of pH 1, 4, 7.4 and 9. These studies further supported the evidence of complexation between clopidogrel and statins as the area under the curve (AUC) was found increased in almost all four pH solutions.

Simultaneous determination of moxifloxacin (MOX) and H2-antagonists was first time developed in bulk and formulations. Purospher STAR C18 (250 x 4.6 mm, 5 μm) column was used. The mobile phase (methanol: water: ACN, 60:45:5 v/v/v, pH 2.7) was delivered at a flow rate of 1.0 mL min-1, eluent was monitored at 236, 270 and 310 nm for cimetidine, famotidine and ranitidine, respectively. The proposed method is specific, accurate (98-103%), precise (intra-day and inter-day variation 0.098-1.970%) and linear (r>0.998). The LOD and LOQ were 0.006-0.018 and 0.019-0.005 μg mL-1, respectively. The statistical parameters were applied to verify the results. The method is applicable to routine analysis of formulations and interaction of MOX with H2-antagonist.

The present paper describes the effect of metals ions on the in vitro availability of enoxacin (a second generation quinolone antibiotic) owing to drug-metal interaction. These interaction studies were performed at 37 °C in different pH environments simulating human body compartments and were studied by UV spectroscopic technique. In order to determine the probability of these reactions different kinetic parameters (dissolution constants (K) and free energy change (ΔG)) for these reactions were also calculated. It is proposed that the structure of enoxacin contains various electron donating sites which facilitate its binding with metallic cations forming chelates. Hence taking food products, nutritional supplements or multivitamins containing multivalent cations at the same time as enoxacin, could reduce the absorption of the drug into the circulation and thus would decrease the effectiveness of the drug. In addition, the MIC of enoxacin for various microorganisms before and after interaction with metal ions was calculated which in most cases was increased which possibly could impair the clinical efficacy of the drug.