OBJECTIVES: To perform clinical and economic evaluation of colistimethate sodium (CS) used in Pseudomonas aeruginosa-related lung infection therapy for patients with cystic fibrosis (CF) from the Bulgarian health insurance system point of view.

METHODS: A systematic review in several internet-based databases (PubMed, clinicaltrials.gov, clinicaltrialsregister.eu) for CS efficacy and safety studies was performed. The direct medical costs of therapy paid by the National health insurance fund (NHIF) for CS were calculated for the period 2016-2018; compared using statistical software MedCalc and extrapolated for the next 3 years applying linear functions.

RESULTS: Patients with CF in Bulgaria are 210 in 2018 and their number is increasing with nearly 20 people each year. According to European Cystic Fibrosis Society guideline, 2018 CS is indicated as only one available option for CF-patients with Ps. aeruginosa-related lung infection who are resistant to other antibiotics. We identified seven studies which demonstrate efficacy and safety of CS for indicated patients. The annual costs for treatment with CS are statistically significant higher each consecutive year rather than the previous one: 156 378.74€ in 2016, 414 301.51€ in 2017 and 512 043.55€ in 2018(p<0,001). A significant difference between the mean monthly costs is revealed: 13 031.56€, 34 525.13€ and 42 670.30€ for 2016, 2017 and 2018, respectively (p<0,001). The share of expenditures for CS from the total expenditures paid by NHIF for ambulatory care rose from 0.04% to 0.12%. Therefore we can assume that probably the number of patients resistant to antibiotics is rising.

CONCLUSIONS: CS is with proved efficacy and acceptable safety profile. Associated costs are relatively high for the Bulgarian health system and show an increasing tendency for the next 3 year period. Reasons for the increase in patients on CS should be further examined.