The assessment of renal function in relation to the use of drugs in elderly in nursing homes; a cohort study

BACKGROUND: Renal function decreases with age. Dosage adjustment according to renal function is indicated for many drugs, in order to avoid adverse reactions of medications and/or aggravation of renal impairment. There are several ways to assess renal function in the elderly, but no way is ideal. The aim of the study was to explore renal function in elderly subjects in nursing homes and the use of pharmaceuticals that may be harmful to patients with renal impairment. METHODS: 243 elderly subjects living in nursing homes were included. S-creatinine and s-cystatin c were analysed. Renal function was estimated using Cockcroft-Gault formula, Modification of Diet in Renal Disease (MDRD) and cystatin C-estimated glomerular filtration rate (GFR). Concomitant medication was registered and four groups of renal risk drugs were identified: metformin, nonsteroidal anti-inflammatory drugs (NSAID), angiotensin-converting enzyme -inhibitors/angiotensin receptor blockers and digoxin. Descriptive statistics and the Kappa test for concordance were used. RESULTS: Reduced renal function (cystatin C-estimated GFR < 60 ml/min) was seen in 53%. Normal s-creatinine was seen in 41% of those with renal impairment. Renal risk drugs were rather rarely prescribed, with exception for ACE-inhibitors. Poor concordance was seen between the GFR estimates as concluded by other studies. CONCLUSIONS: The physician has to be observant on renal function when prescribing medications to the elderly patient and not only rely on s-creatinine level. GFR has to be estimated before prescribing renal risk drugs, but using different estimates may give divergence in the results.