My 86 year old mom (cute as a bug) takes coumadin, about 7-9 mg. a
day.  She has an enlarged heart but she still exausts me!!!!  She used
to take Dilantin, not for any sort of seizures but as an
anti-depressant.  I looked on the Internet and saw that there was some
sort of a negative interaction between Coumadin and Dilantin so she
stopped taking it.  She lives in a remote desert community and goes to
a local doctor in the remote desert community where she lives, who has
said that he was unfamiliar with the reaction between Coumadin and
Dilantin so, she could take it if she wishes.  I AM NOT ASKING FOR
MEDICAL ADVICE. I remember researching this (with my limited
capatilities) and finding a number of sites that said that taking
Dilantin affected the level of Coumadin.  I live on the Gulf Coast and
Ivan is coming for an unvited visit so, I just do not have any time to
spend on this.  My mom is wanting to go back to Dilantin and also
wants to take Bilberry for her macular degeneration.  I will take
whatever information you can give me on how Dilantin and/or Bilberry
will affect Coumadin levels. . . whew!!  thanx so much. . . . any of
you who know Pink, tell her that she is in my constant prayers. 
thanx.

Hello, Carolyn!

Thank you for the prayers. They are deeply appreciated. 

Both Dilantin (phenytoin) and bilberry should generally be avoided by
a person who is taking Coumadin. Coumadin (warfarin) is an
anti-clotting agent, or blood thinner. Dilantin tends to increase the
blood-thinning abilities of Coumadin, and the anthocyanidins in
bilberry also tend to increase this activity. If your mom were to take
all these substances together, the unpredictability of their
interactions would necessitate daily monitoring of your mother's
prothrombin time and other blood testing. Unless there is a compelling
medical reason for combining these chemical agents, it would probably
be best not to take the risk.

"Drugs Which Interfere with Coumadin® Regulation
 Increased Coumadin® Effect
 Highly Probable...

Phenytoin (Dilantin®)"
 
Wilford Hall Medical Center: Coumadin® Interaction With Other Drugs
http://www.whmc.af.mil/coumadin/drginter.htm

"Dangerous Drug Interaction: Warfarin-Phenytoin

Impact: Potential for increased effects of warfarin and/or phenytoin

Mechanism of Interaction: Currently unknown, but one theory suggests a
genetic basis involving liver metabolism of warfarin and phenytoin.
Phenytoin may increase the effects of warfarin.

Alternatives to Patient Management: Obtain baseline phenytoin levels
prior to initiation of warfarin. Monitor INR during co-administration.
Target INR should be towards the lower end of the therapeutic goal
range.

Monitoring/Precautions: INR and phenytoin levels should be monitored
during co-administration. Signs and symptoms of an active bleed should
be monitored daily with particular attention to the appearance and
patterns of bruises."

American Medical Directors Association
Dangerous Drug Interaction: Warfarin-Phenytoin
http://www.amda.com/m3/warfarin_phenytoin.htm

"Do not take bilberry without first talking to your doctor if you have
a bleeding or blood clotting disorder; if you are taking a medicine to
prevent blood clots; or if you are taking other medications, herbs,
antioxidants, or health supplements (these may also affect blood
clotting). Bilberry may affect the time it takes for the blood to
clot...

What other drugs will affect bilberry? 
 ?  Do not take bilberry without first talking to your doctor if you
are taking any of the following medicines:
      · warfarin (Coumadin); 
      · aspirin; 
      · a nonsteroidal anti-inflammatory drug (NSAID) including
ibuprofen (Advil, Motrin, Nuprin, others), naproxen (Aleve, Naprosyn,
Naprelan, Anaprox, others), ketoprofen (Orudis KT, Orudis),
indomethacin (Indocin), etodolac (Lodine), nabumetone (Relafen),
oxaprozin (Daypro), piroxicam (Feldene), sulindac (Clinoril), tolmetin
(Tolectin), and others;
      · ardeparin (Normiflo); 
      · dalteparin (Fragmin); 
      · danaparoid (Orgaran); 
      · enoxaparin (Lovenox); 
      · heparin; or 
      · other herbs, antioxidants, or health supplements (these may
affect blood clotting).
 ?  You may not be able to take bilberry, or you may require special
monitoring during treatment if you are taking any of the medicines
listed above."

Drugs.com: Bilberry
http://www.drugs.com/MTM/bilberry.html 

"Possible Interactions 
 Blood-thinning medications, anticoagulants

In theory, because the anthocyanidins in bilberry may inhibit blood
from clotting, there may be an increased risk of bleeding in those
taking anthocyanidin extracts from bilberry along with blood thinners,
particularly warfarin. This has not been tested scientifically, but
those taking warfarin or other blood thinners in the same class, known
as anticoagulants, should be very careful if considering use of
bilberry and should be followed closely by a doctor who will check
your INR (a measurement to indicate, in part, your risk of bleeding)."
 
Health and Age: Bilberry
http://www.healthandage.com/html/res/com/ConsHerbs/Bilberrych.html

Google search strategy:

Google Web Search: dilantin OR phenytoin coumadin OR warfarin
://www.google.com/search?hl=en&ie=UTF-8&q=dilantin+OR+phenytoin+coumadin+OR+warfarin

Google Web Search: bilberry coumadin OR warfarin
://www.google.com/search?hl=en&ie=UTF-8&q=bilberry+coumadin+OR+warfarin

I hope this helps. Bless you for taking the time to investigate
matters related to your mother's medical care.

Best always,
Pink

As always - the best possible research pointers and the best possible
answer.  You are great and . . . . often in my prayers.

i would probably request the doctor to give her a different anti
-depressant. dilantin is not a mainstream anti-depressant, has a
fairly high side effect profile, involves also checking dilantin level
blood tests and does not sound necessary in the situation which you
describe.

a board certified opthalmologist should handle the macular
degeneration.  she should defer to his or her suggestions. i
personally am unfamiliar with bilberry.

coumadin use is fairly straightforward.  an extra i.n.r. blood
thickness level can be done about 2or 3 weeks after any new
medications are added or subtracted and the effect of the change can
be countered by a tweak in the coumadin dosing.
hopefully her doctor is extremely diligent, it is more important with
coumadin using patients than in many other patients.consider a call to
her doctor to get a feel for the compassion and efficiency of the
doctor and staff.

good luck