Initiation of sulfonylureas versus metformin is associated with higher blood pressure at one year

Pharmacoepidemiology and Drug Safety, 04/06/2012

Compared with metformin, sulfonylurea initiation was associated with increased systolic blood pressure (BP) at 12 months, which appears to be mediated by the differential effects of these drugs on body mass index (BMI).

Methods

  • A retrospective cohort of veterans with hypertension who initiated metformin (n=2057) or sulfonylurea (n=1494) between 1 January 2000 and 31 December 2007 in the Veterans Administration Mid–South Network was assembled.
  • Patients were included if they had complete covariates, including 12–month BP and BMI, and persisted on therapy for 12 months.
  • Linear regression was conducted to investigate the effect of OADs on 12–month systolic BP adjusting for demographics, glycated hemoglobin, creatinine, BMI, health care utilization, and comorbidities, including cardiovascular disease (CVD).
  • A second analysis examined if these effects were mediated by BMI change.
  • The secondary outcome was the proportion of patients who had a controlled BP (≤140/90 mmHg) at 12 months adjusted for baseline BP and covariates.

Results

  • Patients were white (82%) males (97%) with median age of 64 years (interquartile range [IQR] 57, 72), and 27% had history of CVD.
  • Sulfonylurea users had a 1.33 mmHg (0.16, 2.50, p=0.03) higher 12–month systolic BP than metformin users.
  • The median change in BMI from OAD initiation to 12 months was –0.76 (IQR –1.78, 0.07) and 0.21 (IQR –0.57, 1.03) among metformin and sulfonylurea users, respectively.
  • In a model adjusting for BMI change, the difference in 12–month systolic BP between sulfonylurea and metformin users became insignificant (0.23 (–1.00, 1.45), p=0.72), while one BMI unit change was associated with an increase in 12–month systolic BP of 1.07 mmHg (0.74, 1.40, p<0.0001).
  • At 12 months, 68.3% of metformin patients had controlled BP versus 64.2% of sulfonylurea patients (p=0.01).

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