Evaluation of prescribing practices: risk of lactic acidosis with metformin therapy.
BACKGROUND
The risk of lactic acidosis during metformin therapy is linked to specific and well-documented conditions that constitute contraindications or precautions to use of the agent. We conducted a retrospective evaluation of metformin use to determine whether prescribing practices are in accord with published contraindications and precautions.


METHODS
All patients admitted to the hospital during a 6-month period who received at least 1 dose of metformin were identified through hospital pharmacy records. Patient demographics and clinical characteristics were then evaluated to determine whether metformin was prescribed to patients possessing any of the risk factors associated with development of lactic acidosis.


RESULTS
We identified 263 hospitalizations involving 204 patients who received at least 1 dose of metformin during inpatient admission. Patients had at least 1 absolute contraindication to metformin therapy in 71 admissions (27%). In 29 (41%) of these 71 admissions, treatment with metformin continued despite the contraindication. The most common contraindication, elevated serum creatinine concentration, was present or developed during 32 admissions (12%); however, metformin use was appropriately discontinued in only 8 (25%) of these 32 patients. Of the precautions against metformin use, concomitant administration of cationic agents was the most common, occurring in 97 admissions (37%).


CONCLUSIONS
Many patients are treated with metformin despite having clinical conditions that place them at risk for developing lactic acidosis. To minimize this risk, it is essential that prescribers develop a better understanding of the prescribing guidelines for metformin.
Calabrese
Amy T
AT
Department of Pharmacy and Therapeutics, University of Pittsburgh, University of Pittsburgh Medical Center Health System, 302 Scaife Hall, 200 Lothrop St, Pittsburgh, PA 15213, USA.
Coley
Kim C
KC
DaPos
Stacey V
SV
Swanson
Dennis
D
Rao
R Harsha
RH
D000140:Acidosis, Lactic / Q000139:chemically induced*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000075202:Contraindications; D003404:Creatinine / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy; D004348:Drug Labeling; D019983:Guideline Adherence; D006801:Humans; D007004:Hypoglycemic Agents / Q000009:adverse effects*; D008687:Metformin / Q000009:adverse effects*; D008875:Middle Aged; D010818:Practice Patterns, Physicians'; D012189:Retrospective Studies; D012307:Risk Factors
D007004:Hypoglycemic Agents; D008687:Metformin; D003404:Creatinine