Drugs not to take with tamoxifen: CYP2D6 inhibitors

For quick reference, here is my lay understanding of the list of drugs not to take with tamoxifen, thanks to http://medicine.iupui.edu/flockhart/table.htm.

CYP2D6 inhibitors:

Strong inhibitors:
bupropion (antidepressant, Wellbutrin, Zyban, Budeprion and Buproban)
fluoxetine (SSRI, Prozac)
paroxetine (antidepressant, Seroxat, Paxil)
quinidine (cardiac drug, Quinidine)

Moderate inhibitors:
duloxetine (antidepressant, Cymbalta, Yentreve, and in parts of Europe, Xeristar or Ariclaim)
terbinafine (antifungal, Lamisil in UK, US, France, Canada, Romania and Hungary, also sold under the name Terbisil)

Weak inhibitors:
amiodarone (cardiac drug, Pacerone, Cordarone, Aratac, Arycor, Atlansil)
cimetidine (misc. GI drug, Tagamet)
sertraline (SSRI, Zoloft, Lustral)

The classification information in parentheses after each drug contains a link to the drug info. found on rxlist.com, and the brand name info contains links to the wikipedia article about that drug. Of course, as with anything in a blog or online, check with your doctor before discontinuing or changing drugs etc. The field of pharmacogenetics is evolving rapidly, and what’s right for one person may not be right for the next.

According to the flockhart table explanations: “Inhibitors compete with other drugs for a particular enzyme thus affecting the optimal level of metabolism of the substrate drug which in many cases affect the individual’s response to that particular medication, e.g. making it ineffective.

A Strong inhibitor is one that cause a > 5-fold increase in the plasma AUC values or more than 80% decrease in clearance.
A Moderate inhibitor is one that cause a > 2-fold increase in the plasma AUC values or 50-80% decrease in clearance.
A Weak inhibitor is one that cause a > 1.25-fold but < 2-fold increase in the plasma AUC values or 20-50% decrease in clearance.
All other inhibitors.”

Other inhibitors
celecoxib
chlorpheniramine
chlorpromazine
citalopram
clemastine
clomipramine
cocaine
diphenhydramine
doxepin
doxorubicin
escitalopram
halofantrine
histamine H1 receptor antagonists
hydroxyzine
levomepromazine
methadone
metoclopramide
mibefradil
midodrine
moclobemide
perphenazine
ranitidine
red-haloperidol
ritonavir
ticlopidine
tripelennamine

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1 Comment

Filed under breast cancer, CYP2D6, tamoxifen

One response to “Drugs not to take with tamoxifen: CYP2D6 inhibitors

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