title: Second-line therapy in patients with type 2 diabetes inadequately controlled with metformin monotherapy: a systematic review and mixed-treatment comparison meta-analysis.
abstract: BACKGROUND
  Although there is general agreement that metformin should be used as first-line pharmacotherapy in patients with type 2 diabetes, uncertainty remains regarding the choice of second-line therapy once metformin is no longer effective. We conducted a systematic review and meta-analysis to assess the comparative safety and efficacy of all available classes of antihyperglycemic therapies in patients with type 2 diabetes inadequately controlled on metformin monotherapy.
  
  
  METHODS
  MEDLINE, EMBASE, BIOSIS Previews, PubMed and the Cochrane Central Register of Controlled Trials were searched for randomized controlled trials published in English from 1980 to October 2009. Additional citations were obtained from grey literature and conference proceedings and through stakeholder feedback. Two reviewers independently selected studies, extracted data and assessed risk of bias. Key outcomes of interest were hemoglobin A1c, body weight, hypoglycemia, quality of life, long-term diabetes-related complications, serious adverse drug events and mortality. Mixed-treatment comparison and pairwise meta-analyses were conducted to pool trial results, when appropriate.
  
  
  RESULTS
  We identified 49 active and non-active controlled randomized trials that compared 2 or more of the following classes of antihyperglycemic agents and weight-loss agents: sulfonylureas, meglitinides, thiazolidinediones (TZDs), dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) analogues, insulins, alpha-glucosidase inhibitors, sibutramine and orlistat. All classes of second-line antihyperglycemic therapies achieved clinically meaningful reductions in hemoglobin A1c (0.6% to 1.0%). No significant differences were found between classes. Insulins and insulin secretagogues were associated with significantly more events of overall hypoglycemia than the other agents, but severe hypoglycemia was rarely observed. An increase in body weight was observed with the majority of second-line therapies (1.8 to 3.0 kg), the exceptions being DPP-4 inhibitors, alpha-glucosidase inhibitors and GLP-1 analogues (0.6 to -1.8 kg). There were insufficient data available for diabetes complications, mortality or quality of life.
  
  
  CONCLUSIONS
  DPP-4 inhibitors and GLP-1 analogues achieved improvements in glycemic control similar to those of other second-line therapies, although they may have modest benefits in terms of weight gain and overall hypoglycemia. Further long-term trials of adequate power are required to determine whether newer drug classes differ from older agents in terms of clinically meaningful outcomes.
authors: Canadian Agency for Drugs and Technologies in Health (CADTH), 600–865 Carling Ave., Ottawa, Ontario, Canada.
authors: Brendan
authors: B
authors: McIntosh
authors: Chris
authors: C
authors: Cameron
authors: Sumeet R
authors: SR
authors: Singh
authors: Changhua
authors: C
authors: Yu
authors: Tarun
authors: T
authors: Ahuja
authors: Nicky J
authors: NJ
authors: Welton
authors: Marshall
authors: M
authors: Dahl
mesh_terms: D001499:Bayes Theorem; D001835:Body Weight; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D054873:Dipeptidyl-Peptidase IV Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D018450:Disease Progression; D052216:Glucagon-Like Peptide 1 / Q000031:analogs & derivatives / Q000627:therapeutic use*; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007003:Hypoglycemia / Q000517:prevention & control; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D008687:Metformin / Q000008:administration & dosage / Q000627:therapeutic use*; D012307:Risk Factors; D013997:Time Factors; D017211:Treatment Failure
chemical_list: D054873:Dipeptidyl-Peptidase IV Inhibitors; D052216:Glucagon-Like Peptide 1; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D008687:Metformin