Two studies from the National Institutes of Health (NIH) suggest that a widely used herbal product - St. John's wort - could significantly compromise the effectiveness of several prescription medicines. The herb speeds up activity in a key pathway responsible for breaking these drugs down in the body. When the medications are taken with St. John's wort, the end result is that blood levels of the drugs decrease because the body breaks them down faster.
HIV Patients Should Avoid St. John's Wort
St. John's wort especially affects indinavir and other protease inhibitors (including nelfinavir, amprenavir, ritonavir, and saquinavir) used to treat HIV infection. These drugs are among the most potent agents available for treating HIV infection and have been shown to prolong survival and slow the progression of the disease. Substances in both St. John's wort and in indinavir are thought to share a metabolic pathway, which suggested the probability of the drugs' interaction. The active ingredient in St. John's wort is suspected to induce drug metabolism, which revs up the rate the liver eliminates indinavir from the body. Consequently, there's not enough indinavir in the blood to do the job it's designed to do. The findings have been detailed in the British medical journal The Lancet.
Other Cautions Advised in Herbal Use
Based on reports in medical literature, St. John's wort appears to be an inducer of an important metabolic pathway, cytochrome P450. Many prescription drugs used to treat conditions such as heart disease, depression, seizures, and certain cancers; or to prevent conditions such as transplant rejection or pregnancy (oral contraceptives) are metabolized via this pathway.
St. John's wort should not be used with several prescription medications, including:
- Protease inhibitors amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir
- Tricyclic antidepressants imipramine, amoxapine, and amitriptyline
- Anti-seizure medications such as carbamazepine, phenytoin, or phenobarbital
- Cancer medications like tamoxifen, cyclophosphamide, taxol or etoposide
- Cyclosporine, rapamycin, or tacrolimus-drugs used to help prevent organ transplant rejection
- Cholesterol-lowering medications such as lovastatin
- Blood thinners such as warfarin
- Ethinyl estradiol, a drug used during pregnancy
- Nonucleoside reverse transcriptase inhibitors (NNRTIs) delavirdine, efavirenz, and nevirapine
- Heart disease medications such as digoxin, diltiazem, nifedipine, digotoxin, or p-blockers
- Medicines used to treat migraine, such as sumatriptan
In addition, St. John's wort may trigger mania in bi-polar individuals, and may contribute to serotonin syndrome (exhibited by dizziness, faintness, muscle spasms, racing heart, and inability to think clearly.
The Bottom Line
Always consult with your health care provider about these or other potential drug interactions. It is critical you seek the advice of a health care professional before discontinuing the use of products containing St. John's wort (scientific name: Hypericum perforatum), as there are possible toxic effects, which should be monitored. |
