Abstract
Objectives To compare the benefits and harms of metformin and insulin
versus insulin alone as reported in randomised clinical trials of patients
with type 2 diabetes.
Design Systematic review of randomised clinical trials with
meta-analyses and trial sequential analyses.
Data sources The Cochrane Library, Medline, Embase, Science Citation
Index Expanded, Latin American Caribbean Health Sciences Literature,
and Cumulative Index to Nursing and Allied Health Literature until March
2011. We also searched abstracts presented at the American Diabetes
Association and European Association for the Study of Diabetes
Congresses, contacted relevant trial authors and pharmaceutical
companies, hand searched reference lists of included trials, and searched
the US Food and Drug Administration website.
Review methods Two authors independently screened titles and
abstracts for randomised clinical trials comparing metformin and insulin
versus insulin alone (with or without placebo) in patients with type 2
diabetes, older than 18 years, and with an intervention period of at least
12 weeks. We included trials irrespective of language, publication status,
predefined outcomes, antidiabetic interventions used before
randomisation, and reported outcomes.