Objective. To assess the dynamics of the renin (R) and aldosterone (Ald) levels changes, the microalbuminuria (MAU) and arterial hypertension (AH) severity after angiotensin-converting enzyme (ACE) inhibitors withdrawal or their dose decrease as well as to clarify the equivalence of the renin-angiotensin-aldosterone system blockade when replacing the ACE inhibitors (ACEi) (enalapril) with angiotensin II receptor blocker (ARBs, losartan).

Materials and methods. Of 218 children who had hemolytic-uremic syndrome (HUS) in 2005-2014, the study included 13 (6%) of 20 (11%) patients who had received with treatment ACEi (enalapril) for more than 2 years at the time of examination. The age in the main group (Group 1) was 10.3±2.5 years, the post-HUS follow-up period — 8.0 years (4.2; 9.5), the enalapril administration duration — 5.1 years (3.8; 8.1) the dose being 0.13 (0.11; 0.21) mg/kg/day. The comparison group (Group 2) included 17 children with HUS not receiving antihypertensive therapy. The average age in the group was 10.7±2.2 years, the follow-up period — 9.0 years (6.3; 10.0). The control group (Group 3) consisted of 19 healthy children aged 8.8±2.5 years. In 11 children of the main group it was possible to follow the change of R and Ald levels at 4 points: 1p — at time of admission to hospital using ACEi, 2p — 7 days after withdrawal or 50% reduction of enalapril dose
(if the initial dose> 0,2 mg/kg/day), 3p — after 4 days and 4p — more than 2 weeks of taking losartan at dose 0,83 (0,78; 0,88) mg/kg/day.

Results. While enalapril was taken, the renin levels were significantly higher in Group 1 as compared to Groups 2 and 3 while there was no difference between the groups in the aldosterone concentrations. A significant decrease of renin level was noted by the 7th day of the enalapril withdrawal the values increasing subsequently again after the losartan appointment. The Ald concentration, on the contrary, increased after the withdrawal of ACEi reaching the maximum in Group 3 returning to the initial level after the ARB taking for more than 2 weeks.

Conclusion. According to the study results, the equivalence of enalapril and losartan effects is confirmed by the serum renin and aldosterone comparable levels when replacing one with the other as well as by achieving a similar effect on MAU and AH values. This makes possible clinicians alternate ACEi and ARBs when it is  necessary to administrate the drug for a long term not losing or reducing the renoprotective effect.