Enalapril (MK421) and its lysine analogue (MK521): a comparison of acute and chronic effects on blood pressure, renin-angiotensin system and sodium excretion in normal man

Br J Clin Pharmacol. 1984 Mar;17(3):233-41. doi: 10.1111/j.1365-2125.1984.tb02337.x.


The immediate and long-term effects of enalapril (MK421) and its lysine analogue (MK521) in once-daily dosage, were compared in a study of 12 normal subjects. Both compounds lowered blood pressure equally throughout 24 h without causing tachycardia. The biochemical changes with MK521 were more sustained than with MK421, but this did not affect the magnitude of blood pressure reduction. Twenty-four hours after the previous dose, with both active drugs, plasma renin concentration was significantly higher on day 8 than on day 1, though angiotensin I did not increase in proportion; this probably reflects a fall in renin-substrate with prolonged converting enzyme inhibition. There was an early natriuresis with each compound but this effect was no longer apparent after 8 days of continuous therapy. Both MK421 and MK521 were well tolerated with no serious side effects.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Pressure / drug effects*
  • Dipeptides / adverse effects
  • Dipeptides / pharmacology*
  • Dose-Response Relationship, Drug
  • Electrolytes / blood
  • Enalapril
  • Heart Rate / drug effects
  • Humans
  • Lisinopril
  • Male
  • Natriuresis / drug effects*
  • Renin-Angiotensin System / drug effects*
  • Time Factors


  • Dipeptides
  • Electrolytes
  • Enalapril
  • Lisinopril