The cranberry thing has no substance to it. It was spawned by some screwy study....Well I'll find and post the thing.
UPDATES:
http://www.warfarinfo.com/cranberry.htm
A study by Lilija et al found that cranberry juice had no effect on the enzymes responsible for the metabolism of warfarin, therefore it is very unlikely that any interaction occurs. Drinking cranberry juice daily caused no effect on the action of warfarin.
A study by Mohammed et al. found that when a person was pre-treated with cranberry and then given a dose of 25 mg of warfarin that the area under the INR-Time curve was increased by 30% compared to the warfarin dose alone. There are two enzyme systems that are affected by warfarin; the VKORC1 (the site where warfarin affects the slowing of the activity of vitamin K), and CYP450-2C9 (the site where the body rids itself of warfarin). Most studies have been associated with the -2C9 system. However, more knowledge is being gained about the VKORC1 system and it appeared from this study that this was the site involved. This would explain much of the controversy over whether or not there is an interaction.
References
Committee on Safety of Medicines. Possible interaction between warfarin and cranberry juice. Current Problems in Pharmacovigilance 2003;29(Sept)8.
Committee on Safety of Medicines. Interaction between warfarin and cranberry juice: new advice. Current Problems in Pharmacovigilance 2004:30(Oct)10.
Greenblatt D. Cranberry juice and warfarin: Is there an interaction? Anticoagulation Forum 2006;10(Spring)1-4.
Greenblatt D, vonMoltke L, Perloff E, Luo Y, Harmatz J, and Zinny M. Interaction of flurbiprofen with cranberry juice, grape juice, tea, and fluconazole: in vitro and clinical studies. Clinical Pharmacology and Therapeutics 2006;79;125-133.
Rindone J and Murphy T. Warfarin-cranberry juice interaction resulting in profound hypoprothrombinemia and bleeding. American Journal of Therapeutics 2006 May-Jun;13(3):283-284.
Lilija JJ et al. Effects of Daily Ingestion of Cranberry Juice on the Pharmacokinetics of Warfarin, Tizanidine, and Midazolam-Probes of CYP2C9, CYP1A2, and CYP3A4. Clin Pharmacol Ther. 2007 Mar 28; Epub ahead of print.
Mohammed AMI et al. Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects. Br J Pharmacol. 2008 Jun 2. [Epub ahead of print
Grapefruit juice...I even drink it, but not until at least 4 hours after taking the Coumadin. Don't drink it at the same time as taking the med. If your on other meds, then I wouldn't advise it. Grapefruit juice can cause problems with alot of meds.
http://www.warfarinfo.com/grapefruit-juice.htm