Does Polyvinylpyrrolidone Improve the Chemical Stability of Cilazapril in Solid State?

In this study a solid dispersion and a physical mixture of cilazapril (CIL) with a biopolymer - polyvinylpyrrolidone (PVP) as a carrier were prepared so as to investigate the effect of PVP on the stability of CIL. CIL is unstable in solid state and decomposes rapidly under humid conditions. It requires stabilization to ensure safety of its use. The studied CIL/PVP formulations were prepared by milling and evaporation technique. Their identity was confirmed by FT-IR method. The stability of CIL in the CIL/PVP formulations was assessed by forced ageing test under isothermic conditions using RP-HPLC. The influence of temperature (experimental conditions: RH 76.4% and T = 70, 75, 80, 85, and 90 oC) and the effect of relative humidity (experimental conditions: RH 25.0%, 50.9%, 60.9%, 66.5%, 76.4%, T = 90 °C) on the rate of CIL degradation were examined. It was established that the process of CIL decay in the studied forms followed first-order kinetics with the formation of one degradation product - cilazaprilat. The degradation rate constant of this reaction was lower than that for pure CIL. The energy of activation of the CIL degradation in the presence of PVP was higher than that of pure CIL. Furthermore, CIL incorporated into PVP exhibited lower sensitivity to moisture. Based on these data PVP was considered as a potential stabilizing substance for CIL-containing dosage forms.

Thermo-, Radio- and Photostability of Perindopril Tert-butyloamine in The Solid State. Comparison to Other Angiotensin Converting Enzyme Inhibitors.

The main aim of this study was determination of thermo- radio- and photostability of perindopril tert-butyloamine (PER) therefore the efficiency and safety of the therapy could be maintained. A chromatographic method (RP-HPLC) had been validated before use to determine PER loss. The evaluation of stability properties of PER in solid state under the influence of isothermal condition, relative humidity - RH = 0% and 76.4%, exposure to 6 mln lux h and ionizing radiation generated by beam of electrons of 25-400 kGy was investigated. Studies pointed out that presence of moisture changes a kinetic model of PER degradation; lack of moisture in the air generates a first-order kinetic model of the reaction, increase humidity generates the autocatalytic model. PER proved to be resistant for ionizing radiation. It is possible to use radiation sterilization and decontamination (dose 25 kGy) with no significant loss of content. Investigation of PER photostability proved, that after exposure to 6 mln lux h physicochemical parameters are acceptable. Among all the ACE-I, PER has one of the shortest t0,5. PER should be stored in closed containers, protected from high temperature and moisture. PER is referred to be photostable and resistant for radiodegradation.

Unknown face of known drugs - what else can we expect from angiotensin converting enzyme inhibitors?

The renin-angiotensin system (RAS) is one of important systems among homeostatic mechanisms that control the function of cardiovascular, renal and adrenal systems. As RAS has a very complex nature, it has been also found as related to the control of cell migration and apoptosis. Angiotensin-converting enzyme inhibitors (ACEI) are drugs most commonly used in the modulation of RAS activity. ACEI have been extensively described as effective in the treatment of hypertension among adults, but also as drugs delaying progression in diabetic nephropathy and reducing mortality in left ventricular dysfunction and congestive heart failure. What is less obvious, ACEI are also widely used in pediatric nephrology and cardiology. Moreover, there are more and more reports showing evidence that ACEI can be beneficial in the treatment of many other diseases and the pleiotropic activity of ACEI is mainly based on their antioxidant properties. In this paper we focus on the less obvious possibilities of the clinical use of ACEI in neurological or oncological patients, discuss the role of ACE gene polymorphism and show the perspectives of potentially new applications of ACEI in contemporary pharmacotherapy.

Chemistry and pharmacology of Angiotensin-converting enzyme inhibitors.

The renin-angiotensin system has been established as an attractive target for pharmacological intervention since the discovery of first angiotensin-converting enzyme inhibitors (ACE-Is). In fact, these drugs are primarily used in the management of cardiovascular system-related diseases and renal insufficiency. Their mechanism of action involves the adjustment of balance between vasoconstrictive, hypertrophic and salt/water-retentive angiotensin II and vasodilatory and natriuretic bradykinin by the inhibition of angiotensin II biosynthesis and bradykinin degradation. Currently there are thirteen family members approved for use in humans. They differ in structure, chemistry and pharmacokinetic and pharmacodynamic properties yet they display a similar pharmacologic and toxicologic profile. All of them are effective in the treatment of hypertension as well as in cardiac insufficiency or diabetic nephropathy. Although they are generally well-tolerated several serious side-effects including life-threatening angioedema, renal failure and persistent dry cough could occur during the administration of ACE-Is, which may require the cessation of therapy. Furthermore, to provide maximum safety and efficiency of ACE-Is-based therapy, the knowledge of the related drug interactions and chronokinetics seems to be an absolute requirement. Here we discuss the above-mentioned issues regarding the pharmaceutical and chemical properties of the commercially- used ACE-Is.