Metformin as RenoProtector of Progressive Kidney Disease

The intervention consists in the treatment of patients with progressive kidney disease and blindly randomized to the treatment group with metformin as medication, added to their usual treatment. Metformin is a well-known and cheap medication used for many years and still used as main treatment of type 2 diabetes. In our study, this 'old' product will be used for a 'new' indication, slowing down the progression of CKD. After randomization in the participating renal care clinic, patients in the intervention group will be treated with metformin at a dose of 1000 mg/day (2x500mg) in the evening during 30 months (Metformin - Glucophage SR (Merck KGaA)). During the first month of the trial a dose of 1x500mg will be used in order to avoid as much as possible some well-known mainly gastrointestinal side effects of metformin treatment At each visit during the study period, the metformin medication will be hand over to the patient in a HDPE bottle, closed with a MEMS cap (Medication Event Monitoring System). The MEMS a cap that registers the time and date of each opening (presumed intake of the medication in the bottle). Patients blindly randomized to the control group will receive placebo treatment (2 tablets per day) also in a MEMS device and will continue to receive usual care. Control patients will have the same data collection. Follow-up of patients during the entire study period will be the responsibility of the treating nephrologist in the renal care clinic. All patients will have a baseline data collection at study entry (demographics, comorbidities, concomitant medication, clinical parameters, lab results). During the study period of 30 months patients will have follow-up visits at their renal care clinic every four months with collection of follow-up data (concomitant medication, clinical parameters, routine lab results and drug related problems). Extra blood and urine samples will be collected for a centralized second determination of serum creatinine and proteinuria.