title: Sulfonylurea versus metformin monotherapy in patients with type 2 diabetes: a Cochrane systematic review and meta-analysis of randomized clinical trials and trial sequential analysis.
abstract: BACKGROUND
  Guidelines recommend metformin as the first-line oral treatment for type 2 diabetes. We conducted a systematic review to assess whether the use of second- and third-generation sulfonylurea agents is associated with benefits and harms in terms of patient-important outcomes compared with metformin.
  
  
  METHODS
  We searched several electronic databases and other sources for randomized clinical trials published to August 2011. We included trials that compared sulfonylurea versus metformin monotherapy among patients 18 years or older with type 2 diabetes and that had an intervention period of at least 24 weeks. We assessed risk of bias and extracted data related to interventions and outcomes. The risk of random errors was assessed by trial sequential analysis.
  
  
  RESULTS
  We included 14 trials (4560 participants). All trials were judged to be at high risk of bias. Data on patient-important outcomes were sparse. Compared with metformin, sulfonylurea did not significantly affect all-cause mortality (relative risk [RR] 0.98, 95% confidence interval [CI] 0.61 to 1.58) or cardiovascular mortality (RR 1.47, 95% CI 0.54 to 4.01). Sulfonylurea significantly decreased the risk of nonfatal macrovascular outcomes (RR 0.67, 95% CI 0.48 to 0.93). However, the definition of this outcome varied among trials, and trial sequential analysis showed that more trials are needed before reliable conclusions can be drawn. No differences between sulfonylurea and metformin were found for change in fasting blood glucose level or glycosylated hemoglobin concentration in the random-effects model. Sulfonylurea resulted in greater weight gain compared with metformin, a finding confirmed in the trial sequential analysis. Significantly more patients in the sulfonylurea arm than in the metformin arm had mild hypoglycemia (RR 2.95, 95% CI 2.13 to 4.07) and severe hypoglycemia (RR 5.64, 95% CI 1.22 to 26.00).
  
  
  CONCLUSIONS
  Some evidence suggests that, compared with metformin, second- and third-generation sulfonylureas may not affect all-cause or cardiovascular mortality but may decrease the risk of nonfatal macrovascular outcomes among patients with type 2 diabetes. They may also increase the risk of hypoglycemia. In general, the available data were too few and inconsistent to provide firm evidence concerning patient-important outcomes in relation to the benefits and harms of sulfonylurea versus metformin monotherapy.
authors.affiliation: Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Bianca
authors.initials: B
authors.lastname: Hemmingsen
authors.affiliation: Nordic Cochrane Centre, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Jeppe B
authors.initials: JB
authors.lastname: Schroll
authors.affiliation: Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Jørn
authors.initials: J
authors.lastname: Wetterslev
authors.affiliation: Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Gluud
authors.affiliation: Department of Endocrinology, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Allan
authors.initials: A
authors.lastname: Vaag
authors.affiliation: Department of Internal Medicine, Copenhagen University Hospital Gentofte, University of Copenhagen, Hellerup, Denmark.
authors.forename: David P
authors.initials: DP
authors.lastname: Sonne
authors.affiliation: Department of Anaesthesiology, Nordsjællands Hospital, Hillerød, Denmark.
authors.forename: Lars H
authors.initials: LH
authors.lastname: Lundstrøm
authors.affiliation: Department of Internal Medicine, Copenhagen University Hospital Gentofte, University of Copenhagen, Hellerup, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Almdal