St. John's Wort

Possible Drug Interactions

One of the major downsides of using St. John’s wort is that it may interact in a potentially harmful way with many common medications. It's broken down in the liver by enzymes that also process certain medications. The result is that it can decrease the effectiveness of other medications a person is taking or increase the effect, leading to an increased risk of adverse effects.

Avoid taking the following with St. John's wort:

• Alcohol

• Allergy drugs, such as Allegra (fexofenadine)

• Antibiotics, such as Cipro (ciprofloxacin) and Achromycin (tetracycline)

• Antidepressants - St. John’s wort may increase the side effects of certain antidepressants, including Marplan (isocarboxazid), Nardil (phenelzine) and Parnate (tranylcypromine) and other monoamine oxidase inhibitors; Prozac (fluoxetine), Paxil (paroxetine) Zoloft (sertraline) and other selective serotonin reuptake inhibitors (SSRIs); and tricyclic antidepressants, such as Elavil (amitriptyline) and Pamelor (nortriptyline).

• Antifungal drugs, such as Sporanox (itraconazole) and Nizoral (ketoconazole)

• Certain calcium channel blockers, such as Tiazac (diltiazem) and Adalat (nifedipine)

• Cancer medications, such as Camptosar (irinotecan), Gleevec (imatinib), Taxol (paclitaxel), Velbe (vinblastine), and Oncovin (vincristine)

• Cholesterol-lowering statin drugs, such as Mevacor (lovastatin), Lipitor (atorvastatin), and Zocor (simvastatin)

• Dextromethorphan (DM), an ingredient in many non-prescription cough and cold products to relieve cough. Use with St. John's wort may increase serotonin levels, resulting in a greater risk of adverse effects.

• Drugs that suppress the immune system, such as Imuran (azathioprine), CellCept, Neoral (cyclosporine), Prograf (tacrolimus), Rapamune (sirolimus), Zenapak (daclizumab)

• Digoxin – St. John’s wort may reduce its effectiveness

• Iron – St. John’s wort blocks the absorption of iron

• Imodium (loperamide) – A case report of deliurium developing in an otherwise healthy woman taking St. John’s wort and the antidiarrhea medication loperamide.

• Serzone (nefazodone)

• Non-nucleoside reverse transcriptase inhibitors, such as Rescriptor (delavirdine) and Viramune (nevirapine)

• Oral contraceptives – St. John’s wort has been known to cause breakthrough bleeding and may decrease the effectiveness of birth control pills.

• Protease inhibitors such as Crixivan (indinavir), Norvir (ritonavir), Viracept (nelfinavir)

• Psoralen medications, such as methoxsalen or Oxsoralen (8-MOP)

• Reserpine – St. John’s wort blocks the effect of this drug

• Sedative drugs – when used together with St. John’s wort, the sedative effect may be exaggerated

• Sedative herbs, such as catnip, hops, kava and valerian

• Aerolate, T-Phyl, and Uniphyl (theophylline) – St. John’s wort may reduce the effectiveness of theophylline, a medication used for asthma, emphysema and chronic bronchitis

• Triptans such as Imitrex and Amerge (sumatriptan), Axert (almotriptan), Frova (frovatriptan), and Zolmig (zolmitriptan)

• Coumadin (warfarin) – St. John’s wort may reduce the effectiveness of warfarin, increasing the risk of blood clots. St. John’s wort may possibly influence the effectiveness of other anticlotting drugs or similar drugs known as antiplatelet drugs.

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