title: Reduction of blood pressure variability by combination therapy in spontaneously hypertensive rats.
abstract: OBJECTIVE
  To test the hypothesis that combination therapy might be a powerful tool to reduce blood pressure variability (BPV) in the treatment of hypertension.
  
  
  METHODS
  In chronic studies, male spontaneously hypertensive rats were given drugs in their rat chow for 18 weeks (n = 9 or 10 for each group of rats). Doses were as follows: atenolol (10 mg/kg per day), amlodipine (1 mg/kg per day), a combination of atenolol and amlodipine (2.5 + 0.25, 5 + 0.5, and 10 + 1 mg/kg per day), hydrochlorothiazide (8 mg/kg per day), enalapril (3.2 mg/kg per day), and a combination of hydrochlorothiazide and enalapril (2 + 0.8, 4 + 1.6, and 8 + 3.2 mg/kg per day). In acute studies, drugs were perfused through the left femoral vein in conscious rats.
  
  
  RESULTS
  In chronic studies, compared with monotherapy, the combinations of two antihypertensive drugs were more effective in reducing the blood pressure (BP), BPV, and organ damage. The indexes of organ damage were all positively related to BP and/or BPV. In acute studies, the constant infusion of phenylephrine (6.25 microg/kg per min) markedly increased the BP, but showed no significant effects on BPV. The infusion of a combination of atenolol and amlodipine (62.5 + 6.25 microg/kg per min) or a combination of hydrochlorothiazide and enalapril (500 + 200 microg/kg per min) significantly reduced the BP and BPV; moreover, a significant reduction in BPV was still found when the rat's BP was restored to control levels by a concomitant infusion of phenylephrine.
  
  
  CONCLUSIONS
  Combination therapy may be a powerful and useful tool for BPV reduction in the treatment of hypertension. In addition to the BP reduction, the decrease in BPV may contribute significantly to the prevention of organ damage in hypertension.
authors.affiliation: Department of Pharmacology, Second Military Medical University, Shanghai, China.
authors.forename: He-Hui
authors.initials: HH
authors.lastname: Xie
authors.forename: Fu-Ming
authors.initials: FM
authors.lastname: Shen
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Xu
authors.forename: Ping
authors.initials: P
authors.lastname: Han
authors.forename: Chao-Yu
authors.initials: CY
authors.lastname: Miao
authors.forename: Ding-Feng
authors.initials: DF
authors.lastname: Su
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects*; D004359:Drug Therapy, Combination; D006973:Hypertension / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR
chemical_list: D000959:Antihypertensive Agents