Development of a pharmacoeconomic model to compare the cost-effectiveness of low versus high dose colistin in the treatment of nosocomial pneumonia caused by Multi-Drug Resistant (MDR) Gram negative bacteria in Saudi Arabia.

Abstract

Introduction The emergence of multi-drug resistant bacteria has led to higher treatment failure and a subsequent increase in patient mortality. Limited treatment options are available for Gram-negative bacteria (GNB) that are resistant to carbapenam antibiotics. Colistin is considered as the last resort treatment options for the carbapenamase producing GNB, though occasional reports of colistin resistance has been noted in the literature. Available studies show efficacy with both doses and with variable levels of adverse effects. In the absence of consensus regarding a dosing strategy for colistin, a model comparing low and high dose colistin in the treatment of nosocomial pneumonia will serve as a useful tool in decision making.

Methods A decision–analytic model using data obtained from a retrospective review of patients treated for nosocomial pneumonia at King Abdulaziz Hospital, Saudi Arabia, was developed to compare the costs and outcomes of low dose versus high dose colistin in the treatment of nosocomial pneumonia caused by colistin-only sensitive bacteria. Outcome measures used in the analysis were length of antibiotics use, length of hospital stay, cure and nephrotoxicity in order to calculate the mean total cost of treatment, incremental costs, cost effectiveness ratios and incremental cost effectiveness ratios.

Results There was a total of 171 patients that received colistin during the study period of which 96 met the inclusion criteria. Of the remaining patients 33 received high dose and 63 received low dose colistin. Low dose colistin was associated with a non-significant 9% lower cure rate than high dose colistin (21% vs 30%, respectively; p=0.292). Low dose colistin was associated with a 22% lower incidence of nephrotoxicity than HDC (30% vs 8%, respectively) which was found to be significant (p=0.004), respectively. Low dose colistin was associated with similar cure rates and greater cost savings resulting from nephrotoxicity being avoided compared to high dose colistin (ICER = -SAR 13, 894.66 per nephrotoxicity avoided).

Conclusion Low dose colistin was not inferior to high dose colistin in terms of clinical cure and had a lower incidence of nephrotoxicity resulting in significant cost avoidance. The cost–benefit profile suggests that low dose colistin could be considered a more cost-effective option than high dose colistin in the treatment of patients with pneumonia caused by MDR-GNB in Saudi Arabia. King Abdulaziz Hospital should adopt the low dose colistin strategy for treatment of nosocomial pneumonia caused by colistin-only sensitive gram negative bacteria while taking cognizance of local resistance patterns.