Antibiotic switch during treatment with antibiotics against respiratory tract infections in ambulatory care in Norway

Objectives: To compare antibiotic treatment failure evaluated as switch from one type of antibiotics to another in ambulatory care. Methods: Data on all dispensed doxycycline, amoxicillin, phenoxymethylpenicillin and macrolides in Norway June 2013 - May 2015, was retrieved from the Norwegian Prescription Database. We computed switch rates for the selected antibiotics on day 1-28 after initial dispensing, and the corresponding odds-ratios, adjusted for patients age and gender, and prescribers specialty. Results: Of 1.860.036 dispensed antibiotics, 103.076 (5.5%) were switched within 28 days. Within 10 days after the index date, the switch rate was highest for phenoxymethylpenicillin (4.1%), followed by amoxicillin (2.5%), macrolides and doxycycline (2.2%). Conclusions: The switch rate after initial dispensing of phenoxymethylpenicillin is higher than that of more broad-spectrum antibiotics. However, it is still low, supporting the recommendation of phenoxymethylpenicillin as first line treatment when an antibiotic is indicated for a respiratory tract infection in primary care.