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Drug Interactions

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The absence of an interaction between warfarin and cranberry juice: a randomized, double-blind trial.

Posted: 
October 19, 2010
Authors: 
Ansell J, McDonough M, Zhao Y, Harmatz JS, Greenblatt DJ.
Journal: 
J Clin Pharmacol 49(7):824-30
Abstract: 

The question of potentiation of warfarin anticoagulation by cranberry juice (CJ) is a topic of biomedical importance. Anecdotal reports of CJ-warfarin interaction are largely unconfirmed in controlled studies. Thirty patients on stable warfarin anticoagulation (international normalized ratio [INR], 1.7-3.3) were randomized to receive 240 mL of CJ or 240 mL of placebo beverage, matched for color and taste, once daily for 2 weeks. The INR values and plasma levels of R- and S-warfarin were measured during the 2-week period and a 1-week follow-up period. The CJ and placebo groups (n=14 and 16, respectively) did not differ significantly in mean plasma R- and S-warfarin concentrations. Eight patients (4 on CJ, 4 on placebo) developed minimally elevated INR (range, 3.38-4.52) during the treatment period. Mean INR differed significantly (P<.02 only="" on="" treatment="" day="" at="" all="" other="" time="" points="" the="" groups="" did="" not="" differ.="" cranberry="" juice="" has="" no="" effect="" plasma="" s-="" or="" r-warfarin="" levels="" excluding="" a="" pharmacokinetic="" interaction.="" small="" though="" statistically="" significant="" pharmacodynamic="" enhancement="" of="" inr="" by="" cj="" single="" point="" is="" unlikely="" to="" be="" clinically="" important="" and="" may="" random="" change.="" enhanced="" warfarin="" anticoagulation="" attributed="" in="" anecdotal="" reports="" represent="" chance="" temporal="" association.="">

Effects of Cranberry Juice on Pharmacokinetics of -Lactam

Posted: 
October 13, 2010
Authors: 
Li M, Andrew MA, Wang J, Salinger DH, Vicini P,
Journal: 
Antimicrob Agents Chemother 53(7):2725-32
Abstract: 

Cranberry juice consumption is often recommended along with low-dose oral antibiotics for prophylaxis for
recurrent urinary tract infection (UTI). Because multiple membrane transporters are involved in the intestinal
absorption and renal excretion of -lactam antibiotics, we evaluated the potential risk of pharmacokinetic
interactions between cranberry juice and the -lactams amoxicillin (amoxicilline) and cefaclor. The amoxicillin-
cranberry juice interaction was investigated in 18 healthy women who received on four separate occasions
a single oral test dose of amoxicillin at 500 mg and 2 g with or without cranberry juice cocktail (8 oz) according
to a crossover design. A parallel cefaclor-cranberry juice interaction study was also conducted in which 500 mg
cefaclor was administered with or without cranberry juice cocktail (12 oz). Data were analyzed by noncompartmental
methods and nonlinear mixed-effects compartmental modeling. We conclude that the concurrent
use of cranberry juice has no significant effect on the extent of oral absorption or the renal clearance of
amoxicillin and cefaclor. However, delays in the absorption of amoxicillin and cefaclor were observed. These
results suggest that the use of cranberry juice at usual quantities as prophylaxis for UTI is not likely to alter
the pharmacokinetics of these two oral antibiotics.

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