The high pressure liquid chromatography (HPLC) was used for the identification of isoniazid (isonicotinic acid hydrazide) in the milk of cattle treated with a dose of 25 mg/kg/day in alternated days. The effect of milk pasteurization on the isoniazid residue concentration was also studied. The drug excretion presented a cyclic variation, with higher levels in the first day after administration (aa), a mean of 1104.48µg/l, and a decrease two days aa, with a mean of 104.12µg/l. Four days after the last administration of the drug it was not possible to identify residues of isoniazid in the milk of treated animals. Body weight and milk yield influenced the amount of the excreted drug, and pasteurization decreased (mean 47.07%) the concentration of isoniazid residue in milk.

A multicomponent ultraviolet (UV) spectrophotometric method was developed and validated for simultaneous determination of delapril (DEL) and indapamide (IND) in tablets employing the partial least squares regression (PLSR) approach. The PLSR method was developed by a multilevel factorial design using 25 synthetic mixtures of drugs and a significant predict model (p < 0.05) were obtained at 225 nm for DEL (r2 = 0.9992) and 243 nm for IND (r2 = 0.9997). Validation parameters such as the specificity, linearity, precision, accuracy and robustness were evaluated in accordance with the ICH requirements, giving satisfactory results within the acceptable range. The proposed PLSR method was successfully applied for simultaneous determination of DEL and IND in fixed dose combinations and can be used as simple alternative to separation techniques.