Background There has been a marked rise in the prescription of vancomycin and aminoglycosides over recent years due to the increase in infections caused by multi-resistant microorganisms. The measurement of their plasma concentrations (Pcs) is necessary to correctly adjust the dosage and minimise the risk of nephrotoxicity.

Purpose To investigate pharmaceutical interventions (PIs) during the pharmacokinetic monitoring of hospitalised patients receiving vancomycin or gentamicin, and to analyse the health outcomes of monitored patients.

Material and methods We conducted a prospective observational study (May–September 2018) of PIs by the Clinical Pharmacokinetics Unit of the Pharmacy Department in a 350-bed general hospital. Inclusion criteria were age ≥18 years and treatment with vancomycin or gentamicin. Exclusion criteria were hospitalisation in the ICU and pre-surgical antibiotic prophylaxis. We gathered data on: sex, age and clinical (serum creatinine (Cr), diagnosis), pharmacological (drug, dosage, suspension motive) and pharmacokinetic variables and on PIs (Bayesian estimation of individual pharmacokinetic parameters: PI-1, maintain schedule; PI-2, modify dose and/or interval; and PI-3, temporary suspension to favour renal drug elimination). Treatment effectiveness was defined by the disappearance of initial symptoms/signs (‘clinical recovery’) or of the initial microorganism in control culture (‘microbiological recovery’). ‘Nephrotoxicity’ was defined by Cr ≥1.4 mg/mL or ≥50% above baseline value.

Results The study included 61 patients (55.7% female) receiving vancomycin (n=39) or gentamicin (n=22) with mean age of 65.9±19.5 years and mean Cr of 0.7±0.5 mg/mL. The main diagnosis was urinary tract (18.0%) or osteoarticular (14.8%) infection; 104 analytical determinations were conducted (69.2% vancomycin, 30.8% gentamicin); and 57.6% of Pcs were outside the therapeutic range. PIs were: PI-1 (42.3%), PI-2 (53.8%) and PI-3 (3.8%). The reasons for vancomycin versus gentamicin suspension were: ‘clinical/microbiological recovery’ (66.6 vs. 31.8%); ‘therapeutic failure’ (2.6 vs. 0.0%); ‘de-escalation’ (7.7 vs. 22.7%); ‘sequential therapy’ (17.9 vs. 40.9%); ‘severe toxicity’ (0.0 vs. 4.5%); or death (5.2 vs. 0.0%). We observed nephrotoxicity in 2.6% of vancomycin-treated patients and 9.0% of gentamicin-treated patients.

Conclusion The pharmacist adds value to antimicrobial optimisation. Dose or interval modification (PI-2) was the most frequent intervention, increasing treatment effectiveness in a large number of patients and minimising as far as possible the risk of nephrotoxicity.

Reference and/or acknowledgements Alcazar CM, et al. Eur J Hosp Pharm 2017;24:A171.

No conflict of interest.