Consecutive antibiotic use in the outpatient setting: an extensive, longitudinal descriptive analysis of antibiotic dispensing data in the Netherlands.

INTRODUCTION: Taking consecutive antibiotic use into account is of importance to obtain insight in treatment within disease episodes, use of 2nd- and 3rd-choice antibiotics, therapy failure and/or side effects. Nevertheless, studies dealing with consecutive antibiotic use are scarce. We aimed at evaluating switch patterns in antibiotic use in the outpatient setting in the Netherlands. METHODS: Outpatient antibiotic dispensing data was processed to antibiotic treatment episodes consisting of single prescriptions or consecutive prescriptions (2006 to 2014). Consecutive prescriptions were categorised into prolongations and switches. Switches were further analysed to obtain antibiotic switch percentages and trends over time. Outcomes were compared with recommendations of Dutch guidelines. RESULTS: A total of 43,179,867 antibiotic prescriptions were included in the analysis, consisting of single prescriptions (95%), prolongations (2%) and switches (3%). The highest switch percentages were found for trimethoprim (7.6%) and nitrofurantoin (5.4%). For fosfomycin, ciprofloxacin, flucloxacillin and trimethoprim we found the highest yearly increase in switching. Amoxicillin/clavulanic acid was most often used as second antibiotic in a switch. A surprisingly high number of 2nd- and 3rd-choice antibiotics are prescribed as first antibiotic in a treatment. CONCLUSIONS: Although the actual reason for a switch is unknown, switch patterns can reveal problems concerning treatment failure and guideline adherence. In general, switch percentages of antibiotics in the Netherlands are low. The data contributes to the knowledge regarding antibiotic switch patterns in the outpatient setting.

The ARRIBA concept: adequate resorption of ribavirin.

BACKGROUND: Adequate ribavirin exposure is essential for optimal sustained virological response (SVR) rates in chronic HCV treatment. It has been proposed that the area under the concentration-time curve up to 4 h after intake of ribavirin (AUC0-4 h) of the first weight-based ribavirin dose should be ≥1.755 mg•h/l to guarantee the highest chance of SVR. Our ARRIBA concept comprises a test dose of ribavirin to select the optimal starting dose to achieve adequate exposure. This study aims to evaluate whether adequate exposure can be achieved after dose advice based on the AUC0-4 h of a single weight-based ribavirin test dose. METHODS: (Formerly) HCV-infected subjects received a single weight-based ribavirin test dose (<75 kg: 400 mg; ≥75 kg: 600 mg) and the AUC0-4 h was calculated. If ribavirin AUC0-4 h was ≥1.755 mg•h/l, subjects received the same dose 4 weeks later; if the AUC0-4 h was <1.755 mg•h/l, an adjusted dose was administered. The ribavirin AUC0-4 h was recorded again. The primary outcome was the proportion of subjects with an AUC0-4 h ≥1.755 mg•h/l after the second dose. RESULTS: A total of 26 subjects were included. The geometric mean (95% CI) ribavirin AUC0-4 h was 1.67 (1.44-1.92) mg•h/l with 9 subjects (35%) reaching the target AUC on day 1. Thus, on day 29, 17 subjects (65%) received an adjusted dose. The geometric mean (95% CI) AUC0-4 h increased to 1.90 (1.62-2.21) mg•h/l and then 16 subjects (62%) had an AUC0-4 h ≥1.755 mg•h/l, which is significantly higher than day 1 (P<0.05). CONCLUSIONS: Our ARRIBA concept of a ribavirin test dose, with dose adjustment if necessary, leads to an increased proportion of patients with an AUC≥1.755 mg•h/l compared to traditional weight-based ribavirin dosing.