Impact of hydrochlorothiazide on the stability of two perindopril salts. Evaluation of the interaction with HPLC and ESI LC/MS methods
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Perindopril (PER) belongs to the group of the angiotensin converting enzyme inhibitors and is widely prescribed antihypertensive drug. It can be used in monotherapy or in combination therapy for example with hydrochlorothiazide (HTH). As on the market there is no pharmaceutical formulation containing both drugs and in literature has not been reported any work about effect of HTH on PER degradation process, the primary objective of this study was the assessment of stability of two salts of perindopril - tert-butylamine (PERt) and arginine (PERa) in a mixtures model with HTH in different relative humidities and constant temperature. Objective of the study was establishing the mechanisms of drug decomposition in the presence of HTH. Results were achieved using the high performance liquid chromatography (RP-HPLC). The degradation rate constants for mixtures and pure substances were calculated. Decomposition products have been analyzed by ESI LC/MS and the decomposition mechanism for each salt has been proposed. The degradation of PERt in the presence of HTH took place according to autocatalytic reaction kinetic mechanism, described mathematically by Prout-Tompkins equation, and the decomposition process leads to hydrolysis. HTH in the model mixture with PERa generates a first-order kinetic model of the decomposition reaction, and there are two main products of decomposition: product of hydrolysis and diketopiperazine. Our study showed that HTH has statistically significant positive impact on both salts. It can be suggested that PERt or PERa and HTH can be formulated together, hence there is no negative interaction between the drugs.
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