No fanfare as a new antibiotic enters market
It’s big in Japan, but limited use more likely here
It has taken 30 years, but fosfomycin will finally hit the U.S. market in the spring. The antibiotic, widely prescribed overseas, will likely find use here for just one disease: uncomplicated urinary tract infections. Forest Laboratories estimates that 24 million women a year get simple UTIs and that the disease causes seven million lost work days a year in the United States.
A bactericidal agent, fosfomycin disrupts the cell wall of bacteria at a much earlier point than penicillin, says Harvey Schneier, MD, medical director for Forest Laboratories. But despite its efficacy, fosfomycin has one drawback: It accumulates poorly in body tissues, making it an unlikely choice as a chemotherapeutic for anything but UTIs.
"The tissue levels are not good enough to even make this drug worthy for complicated polynephritis," says Schneier. But urine levels of fosfomycin are so high — and remain that way for so long — that simple UTIs can be treated with a single oral dose. In fact, Schneier says, fosfomycin’s killing power lingers for up to 84 hours in the urine. Forest will package the drug in a sachet containing reconstitutable orange-flavored granules.
Fosfomycin’s competition in the marketplace includes a slew of drugs taken in multiple doses for multiple days: amoxicillin/clavulanic acid, nitrofurantoin, norfloxacin and other quinolones, and sulfamethoxazole/trimethoprim. European studies have shown a single dose of fosfomycin just as effective in simple UTIs as five day’s worth of amoxicillin/clavulanate, five day’s worth of norfloxacin, and a week’s worth of nitrofurantoin. Schneier says fosfomycin’s side effect profile compares favorably with the other drugs, with mild, self-limiting diarrhea the most common complaint.
Forest, which will market the drug as Monurol, suggests the product’s cost-effectiveness lies in its single-dose efficacy. Schneier says women with UTIs will sometimes stop taking antibiotics as soon as urinary tract burning stops — usually two or three days into therapy. That could set up a recurrent infection. It also raises the risk of bacterial resistance developing.
Fosfomycin won’t relieve the symptoms any earlier than other drugs, but in terms of compliance, it doesn’t matter since the dose has already been taken. The FDA recommends using another antibiotic if symptoms persist for more than a few days.
Costwise, Schneier estimates Monurol will be cheaper than a multiday course of a quinolone but perhaps more expensive than a few days of therapy with sulfamethoxazole/trimethoprim. He says there’s a safety advantage to using fosfomycin, though. "Fewer patients withdrew [from clinical trials] who had side effects with fosfomycin than who had side effects with SMZ/TMP. Clearly, we think there’s a safety advantage." The question for managed care organizations is whether that advantage is big enough to overcome SMZ/TMP’s low cost.
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