Background and importance Adequate dose titration in patients with renal impairment is crucial to avoid adverse effects and to achieve therapeutic goals. Dose reduction at baseline is not recommended to achieve desired plasma levels and to prevent the development of resistance.

Aim and objectives To assess the inadequacy of prescribed antibiotic doses according to renal function and to identify the medical services involved.

Material and methods Cross-sectional, descriptive study. All patients over 18 years of age with antibiotics prescribed on the day of the cut-off requiring adjustment according to renal function were included; patients admitted to the intensive care unit were excluded. The variables age, sex, prescribing specialty, antibiotic, dose and glomerular filtration rate were collected. Each prescription was reviewed according to our teaching hospital guidelines. Medical history and electronic prescription program were used for data collection.

Results 227 prescriptions for 200 patients (54% men, mean age 68 years) were reviewed. 9.7% of these prescriptions were not correctly adjusted for glomerular filtration rate. Of these, piperacillin/tazobactam was the most commonly prescribed antibiotic with an inadequate dose (45.5%), followed by amoxicillin/clavulanate (27.3%), meropenem (13.6%), vancomycin (9.1%) and gentamicin (4.5%).

The type of adjustment required would have been: dose adjustment (50%), interval modification (27.3%), and both (22.7%). 72.7% of these prescriptions were underdosed and 27.3% overdosed.

In terms of prescribing specialties, Internal Medicine had the highest rate of inadequacy (72.7%), followed by Digestive Medicine (9.1%).

34 of the 227 prescriptions reviewed (15%) required dose adjustment due to glomerular filtration rate below 30 mL/min, of which 35.3% were inappropriately prescribed (20.6% with piperacillin/tazobactam and 14.7% with amoxicillin/clavulanate). Furthermore, 52.9% of them required a first loading dose different from the maintenance doses and in 88.9% of them this was done incorrectly as in most cases the filtrate-adjusted dose was prescribed directly.

Conclusion and relevance A small but not negligible percentage of patients with renal failure do not receive a correct dose. Training physicians in proper prescribing and optimising the pharmaceutical validation process in these patients is essential to ensure their correct use. In addition, this study identifies the need to follow a protocol on the correct initial loading doses and the time required for their adjustment.

Conflict of interest No conflict of interest