Cephalexin Dosing in Cystitis

A with dysuria but no fever or flank pain is prescribed cephalexin 500 mg 2x daily. Drug references suggest up to 4x daily dosing.

Should the frequency be changed?

Yes, increase frequency

No, keep frequency

How did others respond?

Reveal the answer

Best Answer

No, keep frequency

Explanation: Pharmacokinetic data shows that 12 hours after a dose of cephalexin that urinary concentrations are still ~50 mcg/mL which is well above the breakpoint. Therefore we expect cephalexin 500 mg 2x daily achieves 100% time > MIC at the site of infection 🤯

Clinical data tells a similar story. A recent study comparing cephalexin 500 mg 2x daily vs 4x daily in uncomplicated cystitis found NO DIFFERENCE in treatment failure rates 🎉

2x daily 💊💊 may be easier for patients to adhere to compared to 4x daily 💊💊💊💊

Though more frequent cephalexin dosing may be required to treat more severe infections, consider managing cystitis with 2x daily dosing and cut patient burden in half ✂️