When is Fidaxomicin Cost Effective for Treating Recurrent C Difficile?

While vancomycin and oral metronidazole have long been mainstays of treatment for Clostridioides difficile (C diff) infection, in 2021 the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) updated their guidelines to recommend the newer antibiotic fidaxomicin as a first-line therapy for patients suffering from C. diff. Studies have shown a reduced risk of recurrent C diff 40 days out from infection when treated with fidaxomicin versus vancomycin, yet prescribing patterns don’t show a big rush to adopt it.

Hypothesizing that fidaxomicin’s higher cost compared to vancomycin is behind this reluctance, a team of scientists based at McGill University in Montreal created a trial designed to determine at what price point fidaxomicin becomes the cost-saving option in both the U.S. and Canada. The researchers did this by estimating the additional cost of the fidaxomicin needed to prevent a recurrence of C diff and compared it with the approximate cost of a C diff recurrence in the 2 countries.

An examination of 3 randomized controlled trials measuring the risks of recurrent C diff infection found an average overall relative recurrence risk of 0.58 (95% confidence interval, 0.46 - 0.74) when using fidaxomicin versus vancomycin. This risk reduction bumped up against the substantial additional cost of fidaxomicin–$38,222 (95% CI, $30,577 - $57,332) in US dollars to prevent 1 recurrence in the U.S. and $13,760 (95% CI, $11,008 - $20,640) in Canadian dollars to prevent 1 recurrence in Canada.

To determine the systemic costs of a C diff recurrence, the team delved into 6 studies that tallied these costs in the USA and 3 that tallied the costs in Canada, then translated these costs into 2022 dollars. They found that the approximate average systemic cost of a C diff recurrence was $15,147 in U.S. dollars and $8806 in Canadian dollars.

The team obtained drug prices from the Veterans Affairs Supply Schedule; using the lowest prices available, they estimated that a 10-day course of fidaxomicin costs $3845.44 USD in the U.S. and $1584 CAD in Canada. Based on these results, the scientists calculated that only if the price of a 10-day supply of fidaxomicin were lowered to $1650 USD would the likelihood of cost equivalence between fidaxomicin and vancomycin reach 50%. Should fidaxomicin’s price fall to $1140 USD for 10 days, the probability of cost equivalence between the drugs would rise to 95%. Basically, at a price of $1140, use of fidaxomicin is very likely to involve a cost savings.

In Canada, at the (then) current fidaxomicin 10-day cost of about $1580 CAD, the researchers calculated a less than 25% chance of it being cost equivalent in terms of preventing the next C diff recurrence. If the 10-day cost dropped to $1150 CAD, there was a cost equivalence likelihood of 50%; at a cost of $860 CAD, the chance of cost equivalence was 95%, making it a good bet for cost savings at that price.

The authors noted that in Canada, because each province has its own drug plan and can negotiate price with manufacturers, reaching this cost-saving price point for fidaxomicin is not out of the question. Things are trickier in the US. “In the USA, such negotiations are generally not currently permitted by Medicare by law; however, negotiation of drug pricing could save the USA billions per year for all drugs, including fidaxomicin,” they wrote. “Individual U.S. insurance companies, particularly ones with large formulary budgets, may have negotiating power to reduce costs.”

The study’s limitations include the fact that any dosing strategies yielding an improvement in vancomycin’s efficacy would impact results, as the 2 drugs are being directly compared. In addition, the efficacy of fidaxomicin in the randomized trials examined was not calculated as far out as day 56, which is within IDSA-SHEA’s timeframe for recurrence. The study also did not include indirect costs of recurrence, such as lost work time and productivity.