Since supplement manufacturers are not required to test the supplements for safety prior to release to the market, and only recall them if there are a large number of deaths and by order of the FDA, we only know about drug interactions from anecdotes or University funded studies that examine this problem.  There are thousands of supplement products on the market with the potential to interact with prescription or over the counter drugs.  Some of the major ones are listed below:

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THEORETICAL BUT NOT CLINICAL INTERACTIONS: Black Cohosh, Echinacea, Garlic, Ginkgo

 

MILD INTERACTION

Kava (Piper methysticum) is used for relaxation and sleep, and has an interaction with CNS depressants such as Xanax or Klonopin to cause excessive sedation and motor reflex dysfunction.  However when taken as prescribed on the bottle, this is only rarely an issue.  However do not take this drug with buprenorphine (Suboxone, subutex) since coma may result.

 

 

MODERATE to SEVERE INTERACTIONS:

Cranberries taken in usual amounts rarely affects other drugs, but in larger amounts can increase the effect of warfarin leading to excessive bleeding internally or externally.

Coenzyme Q10 (ubiquinone) may reduce the effectiveness of coumadin (warfarin) leading to blood clots

Feverfew (daisy family) is used to prevent migraine headaches and the associated nausea and vomiting, but can increase the risk of bleeding in those taking blood thinners such as clopidogrel (Plavix), dabigitran (Pradaxa), Coumadin (Warfarin), aspirin, or Xarelto (rivaroxaban)

Ginsing (inhibits CYP3A in the liver affecting 50% of prescribed drugs since 50% of prescribed drugs are metabolized by this enzyme.   Alprazolam (Xanax), midazolam (Versed), triazolam (Halcion) can cause excessive sedation when taken with ginsing.  Budesonide, dexamethasone (Decadron),  Fluticasone (Flovent), or Methylprednisolone (Depomedrol) can cause Cushing’s syndrome (too much corticosteroid) when taken with ginsing.  Carbamazepine (Tegretol) can cause vomiting/headache, dizziness, or drowsiness.  Colchicine with ginsing can lead to fever, diarrhea, muscle pain, or paresthesia and may be fatal with ginsing.  Disopyramide (Norpace)Pimozide (Orap), and Quinidine can cause cardiac arrhythmias when taken with ginsing.   Hypotension may result if taken Vardenafil (Levitra), Tadalafil (Cialis), sildenafil (Viagra), or Alfuzosin (Uroxatral).   Repaglinide (Prandin) may result in hypoglycemia.  Ginsing should not be taken when taking chemotherapy drugs, ergotamines (for migraines) or Zocor due to muscle breakdown.

Goldenseal  (Hydrastis Canadensis) is used to treat cold and flu symptoms with very weak clinical evidence of effectiveness.  It is a potent inhibitor of CYP3A4 causing interactions with all the drugs listed for Ginsing, but also inhibits CYP2D6.  The latter may cause severe reactions when taking goldenseal plus tamoxifen, codeine, and many antidepressants including venlafaxine (Effexor) and antipsychotics mirtazapine (Remeron), pimozide or thioridazide)

Green Tea is promoted to reduce cholesterol, as a stimulant and cancer antioxidant.  It contains vitamin K that increases blood clotting.   Large amounts of green tea may interfere with warfarin (Coumadin).

Saw Palmetto is used to treat prostate hypertrophy and can interact with other drugs used for the same purpose.  It may also slow blood clotting and interact with warfarin causing excessive bleeding, and with oral contraceptives reducing their effectiveness.

St. John’s Wort (Hypericum perforatum) is used as a “natural” antidepressant but inhibits both of the CYP 3A4 plus CYP 2D6 liver enzymes.  Clinically significant  interactions have been documented with St. John’s wort and the immunosuppressant drug cyclosporine, the antiretroviral agent indinavir, oral contraceptives, coumadin, digoxin, and benzodiazepines, among others.