title: Effects of amlodipine and enalapril on platelet function in patients with mild to moderate hypertension.
abstract: OBJECTIVE
  The aim of this study was to compare the effect of amlodipine and enalapril on platelet aggregation, and platelet production of malondialdehyde in patients with mild to moderate arterial hypertension.
  
  
  METHODS
  A parallel, double-blind, placebo-controlled study was carried out in 24 patients (2 groups of 12 patients each). Initially all patients received placebo for four weeks; then amlodipine, 5 mg daily or enalapril 20 mg daily taken once a day at 7 am. Dosage was doubled after 4 weeks when diastolic blood pressure was > 90 mmHg in sitting position, the treatment was continued for 12 weeks. At the end of placebo and active phases a platelet aggregation test, using adenosine diphosphate, collagen and adrenaline, and a platelet malondialdehyde production test, either in basal conditions (MDA-basal) and after the stimulation of arachidonic acid pathway by adding ethylmaleimide (MDA-activated) were carried out.
  
  
  RESULTS
  Blood pressure was reduced by both agents, enalapril and amlodipine. Enalapril controlled 58.3% of hypertensive patients with an average dosage of 31.7 mg/daily. Amlodipine controlled 75% of patients with a dosage of 7.1 mg/daily. Platelet aggregation was reduced by amlodipine in 15.9% for ADP (10 microM); 17.4% for collagen (2 microg/ml) and 19.9% for adrenaline (2 microM) (p < 0.025). Meanwhile enalapril slightly increased platelet aggregation by 6.7%, 1.3% and 5.6% for the three agents, respectively (p > 0.05, ns). Malondialdehyde was reduced by amlodipine in 45.33% (p < 0.05) for MDA-basal; 3.76% (p > 0.05) for MDA-activated; and the ratio MDA-basal:MDA-activated in 36.79% (p < 0.005). Meanwhile enalapril increased MDA-basal in 2.89%; MDA-activated in 3.58% and reduced the ratio MDA-basal:MDA-activated, in 10.34% (p > 0.05).
  
  
  CONCLUSIONS
  Both agents, enalapril and amlodipine, reduced blood pressure, but only amlodipine reduced platelet aggregation and platelet production of malondialdehyde, indicating its action on the arachidonic acid metabolic pathway.
authors.affiliation: Clinical Pharmacology Unit, School of Medicine, Universidad Centroccidental Lisandro Alvarado, Barquisimeto, Venezuela.
authors.forename: R
authors.initials: R
authors.lastname: Hernández-Hernández
authors.forename: M C
authors.initials: MC
authors.lastname: Armas-Padilla
authors.forename: M
authors.initials: M
authors.lastname: Velasco
authors.forename: A R
authors.initials: AR
authors.lastname: Carvajal
authors.forename: M J
authors.initials: MJ
authors.lastname: Armas de Hernández
authors.forename: J
authors.initials: J
authors.lastname: Guerrero-Pajuelo
authors.forename: B
authors.initials: B
authors.lastname: Pacheco
mesh_terms: D017311:Amlodipine / Q000494:pharmacology / Q000627:therapeutic use*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D002121:Calcium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use*; D004311:Double-Blind Method; D004656:Enalapril / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D010979:Platelet Function Tests
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002121:Calcium Channel Blockers; D010975:Platelet Aggregation Inhibitors; D017311:Amlodipine; D008315:Malondialdehyde; D004656:Enalapril