Why isn’t cefadroxil used more often?

Extract

Cephalexin is the most commonly prescribed oral first-generation cephalosporin in the United States. In 2013, there were 4.77 million Medicare Part D claims for cephalexin prescriptions, making it the fourth most commonly prescribed oral antibiotic overall.¹ Cephalexin is commonly prescribed for the treatment of skin and soft tissue infections as well as uncomplicated urinary tract infection (UTI). In the case of skin and soft tissue infections, the Infectious Diseases Society of America recommends that cephalexin be dosed four times daily.² Cefadroxil, an oral first-generation cephalosporin, has been available for over 30 years. It has the same spectrum of coverage as cephalexin,³ a similar adverse-effect profile,⁴ and similar efficacy⁴ but a dosing frequency half that of cephalexin. Susceptibility cutoff values and methods for determining them are available for cefadroxil, but the former can be extrapolated from values determined for other first-generation cephalosporins, such as cefazolin and cephalexin.

Both cephalexin and cefadroxil are readily absorbed after oral administration and primarily excreted unchanged in the urine. In patients with normal renal function, cephalexin is usually given four times daily; twice-daily dosing can be used for treating a UTI. Cefadroxil, whose 1.5-hour half-life exceeds that of cephalexin (1 hour), has a recommended dosage of 500–1000 mg twice daily in patients with normal renal function or 1000 mg daily for uncomplicated UTI. The reduced frequency of administration for cefadroxil should result in higher medication adherence, compared with cephalexin. The absolute increase in adherence associated with twice-daily dosing, compared with more frequent administration, can be as high as 30%.⁵