Background and Importance Isavuconazole and voriconazole are antifungals that have shown similar clinical efficacy in the treatment of invasive aspergillosis. Isavuconazole has certain advantages such as a lower interaction profile and can be used in patients with renal insufficiency; however, its similar efficacy limits its use in situations where voriconazole is contraindicated.

Aim and Objectives The aim of this study is to describe the proportion of isavuconazole prescriptions in which the use of voriconazole would not be contraindicated.

Material and Methods Descriptive, observational and retrospective study in which all patients over 18 years of age who received isavuconazole in 2021 in a hospital were included. Exclusion criteria were: age less than 18 years, pregnancy or duration of treatment less than 24 hours.

The use of intravenous voriconazole is contraindicated in patients with moderate to severe renal insufficiency (ClCr <50mL/min), in severe hepatic insufficiency (Child-Pugh C) and in combination with CYP450 substrates.

The main variable under study was the proportion of isavuconazole prescriptions in which the use of voriconazole would not be contraindicated.

The following variables were also collected: sex, age, number of days of treatment and mycological culture results.

Patients treated with isavuconazole were obtained from a database of the pharmacy service, sociodemographic and clinical variables from the OrionClinic computer program.

A descriptive statistical analysis was performed using measures of central tendency such as mean and median, through the SPSS v.23^®program.

Results 37 patients treated with isavuconazole were included. Four patients were excluded. The median age was 63 years (24–82) and 68% were male.

Voriconazole was not contraindicated in 65% of the isavuconazole prescriptions. Thirty-five percent of the patients had renal insufficiency. The mean number of days of treatment was 6 ± 4.9 days.

A mycological culture was performed in 89% of the patients, with 78% of the results being negative.

Conclusion and Relevance A high percentage of patients treated with isavuconazole in our critical care unit did not meet the conditions for which it was included in the pharmacotherapeutic guide of the hospital. These results suggest the need for a specific PROA in critical patients or the multidisciplinary elaboration of a protocol for the use of antifungals.

Conflict of Interest No conflict of interest.