Pharmacokinetic and Pharmacodynamic Evaluation of Metformin Treatment in Elderly Patients with Diabetes Mellitus

Since the biguanide metformin lowers blood sugar levels in the absence of insulin secretion it should be useful for elderly patients with type 2 diabetes mellitus. In this study, the authors examined the pharmacokinetics, efficacy and safety of metformin in the elderly. All analyses were conducted on 86 outpatients given metformin hydrochloride tablets continuously. They were divided into two groups according to age : elderly group (age>=65, n=35) and non-elderly group (age<65, n=51). Creatinine clearance (CCr) was significantly lower in the elderly group than the non-elderly group (p<0.001). In 43 patients from whom plasma samples were collected 2-6 hours after taking metformin, the metformin concentration per dose (Cp/D) increased in pace with the decrease in CCr (Cp/D=3.00·CCr-0.595, r=0.413, p<0.001). On the other hand, in the same CCr group, there was no difference in Cp/D between the elderly and non-elderly patients. In 69 patients to whom metformin was newly prescribed, there was no correlation between patient age and decrease in Hemoglobin A1c (HbA1c). In patients with no hepatic dysfunction, the incidence of side effects in the elderly group was the same as that in non-elderly group (23.3% and 24.4%, respectively). In conclusion, since no difference in metformin pharmacokinetics, efficacy or safety was observed between the two patient groups, we consider that metformin is a useful drug for the elderly with normal renal and hepatic function.