Contraindications to metformin therapy in patients with Type 2 diabetes--a population-based study of adherence to prescribing guidelines.
OBJECTIVE
To define the number of people in Tayside, Scotland (population 349 303) with Type 2 diabetes who use metformin, the incidence of contraindications to its continued use in these people and the proportion that discontinued metformin treatment following the development of a contraindication.


METHODS
Retrospective cohort study of the incidence of contraindications to metformin in all patients with Type 2 diabetes using metformin from January 1993 to June 1995. The contraindications of acute myocardial infarction, cardiac failure, renal impairment and chronic liver disease were identified by: the regional diabetes information system, biochemistry database and hospital admissions database and a database of all encashed community prescriptions.


RESULTS
One thousand eight hundred and forty seven subjects (26.3% of those with Type 2 diabetes) redeemed prescriptions for metformin. Of these, 3.5% were admitted with an acute myocardial infarction (71 episodes); 4.2% were admitted with cardiac failure (114 episodes); 21.0% received metformin and loop diuretics for cardiac failure concurrently; 4.8% developed renal impairment; and 2.8% developed chronic liver disease. The development of contraindications rarely resulted in discontinuation of metformin, for example only 17.5% and 25% stopped metformin after admission with acute myocardial infarction and development of renal impairment, respectively. In total, 24.5% of subjects receiving metformin, 6.4% of all people with Type 2 diabetes, had contraindications to its use. There was one episode of lactic acidosis in 4600 patient years.


CONCLUSIONS
This population-based study shows that 24.5% of patients prescribed metformin have contraindications to its use. Development of contraindications rarely results in discontinuation of metformin therapy. Despite this, lactic acidosis remains rare. Diabet. Med. 18, 483-488 (2001)
Emslie-Smith
A M
AM
Tayside Centre for General Practice, Ninewells Hospital and Medical School, Dundee, Scotland, UK. aemslie-smith@fintry.finix.org.uk
Boyle
D I
DI
Evans
J M
JM
Sullivan
F
F
Morris
A D
AD
D015331:Cohort Studies; D000075202:Contraindications; D019992:Databases as Topic; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D003928:Diabetic Nephropathies / Q000453:epidemiology; D004232:Diuretics / Q000627:therapeutic use; D005194:Family Practice / Q000592:standards; D006333:Heart Failure / Q000150:complications; D006801:Humans; D007004:Hypoglycemic Agents; D008107:Liver Diseases / Q000150:complications; D008687:Metformin; D009203:Myocardial Infarction / Q000150:complications; D017410:Practice Guidelines as Topic; D012189:Retrospective Studies; D012606:Scotland
D004232:Diuretics; D007004:Hypoglycemic Agents; D008687:Metformin