Do contraindications to metformin therapy deprive type 2 diabetic patients of its benefits?

Metformin is considered to be the drug of choice in overweight, newly diagnosed type 2 diabetes. Lactic acidosis is stated to be the most serious side effects of metformin therapy. Current available guidelines contain so many ambiguous terms in describing the contraindications to metformin use that they do little to assist in addressing this problem. Moreover, these ambiguous contraindications may deprive many diabetic patients from the benefit of metformin. The aim of the current study was to evaluate the safety of metformin use in the presence of "standard" contraindications to its use. This was a cross sectional study that involved type 2 diabetic patients who were on chronic treatment with metformin. A fasting blood sample was taken from each subject to determine levels of serum creatinine levels, bicarbonate, fasting blood sugar, lactate, insulin, C-Peptide, and metformin plasma concentration. 106 patients were recruited in the study with 68 [64%] females. The mean age was 58 +/- 13 years. The results illustrate that metformin has been prescribed for patients who are listed in the guidelines as having standard contraindications to its use. There were 30 [28%] patients with impaired renal function [Clcr < 60ml/min.] and five with Clcr < 30ml/min. Moreover, 30 [28%] had ischemic heart disease, six [5%] patients were diagnosed as having congestive heart failure, five [4%] with chronic obstruction pulmonary disease, and three [2%] with peripheral vascular disease. Although the numbers of those patients were not large enough to establish and confirm the safety of metformin in the presence of these standard contraindications and precautions, there were no cases of lactic acidosis observed This study along with other studies has revealed that there is vagueness in the available guidelines in prescribing metformin, which led to the different observed practices. This study revealed that metformin is still prescribed to patients with listed contraindications. Clearer guidelines are needed for prescribing metformin with more specific contraindications. For example it would be more beneficial if the degree of heart failure, classified according to the New York Heart Association is specified