Fidaxomicin for Clostridium difficile-associated diarrhoea: epidemiological method for estimation of warranted price

Fidaxomicin is a macrocyclic antibiotic approved in 2011 by the US Food and Drug Administration for treatment of Clostridium difficile-associated diarrhoea (CDAD).

Herein, we present an epidemiological method to estimate, on a case mix basis, and from the perspective of the US health system, the warranted (justifiable) price per day for fidaxomicin, as a percent of the wholesale acquisition cost (WAC) per day for fidaxomicin ($US280).

Data from two randomized controlled studies (Optimer-003 [n = 596] and Optimer-004 [n = 509]) were used to discern the number-needed-to-treat (NNT = 7.1) for sustained clinical response. Sustained clinical response was defined as clinical response at the end of treatment, and survival without proven or suspected CDAD recurrence through 25 days beyond the end of treatment. National data for primary and secondary cases (the case mix) of CDAD (mean hospital length of stay [LOS], and mean cost) were derived from the 2009 US Healthcare Cost and Utilization Project. The method for attribution of hospital LOS for secondary cases of CDAD was derived from a study published by O'Brien et al. in 2007. Comparative regimens of vancomycin were: (i) injectable used orally, 125 mg four times daily (qid; WAC of $US6/day), with use of vancomycin hydrochloride (HCl) capsules, 125 mg qid (WAC of $US106/day) post-hospital discharge; (ii) vancomycin HCl capsules, 125 mg qid; and (iii) vancomycin HCl capsules, 250 mg qid (WAC of $US196/day). Findings are expressed in 2011 US dollars. The study perspective is that of the US health system.

The warranted price per day for fidaxomicin represented 95% of the WAC per day for fidaxomicin compared with use of injectable vancomycin (orally) 125 mg qid (with subsequent use of vancomycin HCl capsules, 125 mg qid post-hospital discharge); 109% of the WAC per day for fidaxomicin compared with use of vancomycin HCl capsules, 125 mg qid; and 141% of the WAC per day for fidaxomicin when compared with use of vancomycin HCl capsules, 250 mg qid.

From the perspective of the US health system, fidaxomicin represents value for money in the treatment of CDAD. The methodology employed in this research has application beyond antimicrobial pharmacotherapy.