Enalaprilat versus cilazaprilat: a comparison of allergic skin reactions in the guinea pig.

ACE-inhibitors have for some time been used in the treatment of hypertension. Apart from inhibiting the conversion of angiotensin I to II, the drugs also affect the metabolism of some inflammatory agents, like bradykinin and substance P. Egg albumin (EA)-sensitized guinea pigs were pretreated with the ACE-inhibitors. Measurement of flare and wheal areas induced by an intradermal injection of EA, showed that enalaprilat significantly increased, whereas cilazaprilat slightly decreased, the reaction area. Enalaprilat also showed an enhancement in histamine and substance P (SP) contents in the skin. In vitro incubation of guinea pig biopsies with enalaprilat potentiated EA- but not SP-induced histamine release. The EA-induced effect was abolished if the animals were pretreated with capsaicin. The conclusion is that cilazaprilat, in contrast to enalaprilat, does not potentiate inflammatory reactions in the guinea pig.

Effects of cilazaprilat and enalaprilat on experimental dermatitis in guinea pigs.

Two non-sulfur containing ACE-inhibitors were tested concerning their local effect on experimental dermatitis in ovalbumin-sensitized guinea pigs. Enalaprilat but not cilazaprilat potentiated the ovalbumin-evoked inflammatory response. Furthermore, enalaprilat clearly enhanced the erythema evoked by substance P, whereas cilazaprilat did not. Concerning, the bradykinin-evoked erythema, enalaprilat significantly potentiated the response, whereas cilazaprilat only caused a slight increase. Our results suggest that different affinities for peptidases involved in degradation of inflammatory peptides can explain differences between the pro-inflammatory properties of enalaprilat and cilazaprilat.