Is there a cranberry:beta-lactam interaction?

 Drinking cranberry juice is often recommended along with taking low-dose antibiotics to prevent recurrent urinary tract infection.

Researchers from the University of Washington, in Seattle evaluated the potential risk of an interaction between cranberry juice and the β-lactam antibiotics, amoxicillin (amoxicilline, Amoxil) and cefaclor (Ceclor) that might lower the effectiveness of the antibiotics.

First, the details.
Amoxicillin-cranberry juice interaction

  • On 4 separate occasions, 18 healthy women took 1 dose of amoxicillin 500 mg and amoxicillin 2 grams by mouth with or without cranberry juice cocktail (8 oz).

Cefaclor-cranberry juice interaction

  • On 2 separate occasions, they took cefaclor 500 mg with or without cranberry juice cocktail (12 oz).

And, the results.

  • Absorption of amoxicillin and cefaclor was delayed.
  • But overall, cranberry juice had no significant effect on absorption or the elimination of either antibiotic from the body via the kidneys.

The bottom line?
The authors concluded that the use of cranberry juice at usual quantities to prevent urinary tract infections isn’t likely to alter how the body handles these to oral antibiotics, and therefore the response to their use.

Since cranberry was listed as one of the trends to watch in 2009, the results of 2 studies of special interest have been published.

  • Researchers from Massachusetts studied how cranberry might lower the risk of urinary tract infections.
  • Researchers from Australia investigated the possible impact of cranberry, on the anticoagulant, warfarin (Coumadin).

7/2/09 20:27 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.