Warning: Avoid Mixing With Prescription Drugs

Herbal medicines are increasingly popular, but many patients do not inform their physicians that they are using these alternative remedies, according to one of the studies released earlier this month by the American Medical Assn. This can be dangerous because some of the herbs affect prescription drugs that patients may also use.

* Chamomile: Contains coumarin, but chamomile’s effects on the body’s anticoagulation system have not been studied. If used with anticoagulants such as warfarin, close monitoring by a doctor is advised.

* Echinacea: May be toxic to the liver if used for more than eight weeks. Should not be used with drugs that can cause liver problems, such as anabolic steroids, amiodarone, methotrexate and ketoconazole. Should not be given with immunosuppressants such as corticosteroids and cyclosporine because it can stimulate the immune system.

* Evening primrose oil and borage: Should not be used with anticonvulsants because these herbs may lower the seizure threshold.

* Feverfew: Effect on migraine headaches may be compromised by nonsteroidal anti-inflammatory drugs, such as aspirin and ibuprofen. Also should not be used with the drug warfarin or other anticoagulants because feverfew inhibits clotting.

* Garlic: Should not be used with warfarin because it affects clotting.

* Ginger: Should not be used with warfarin because it affects clotting.

* Gingko: Can inhibit clotting so should not be used with aspirin or other nonsteroidal anti-inflammatory drugs or with anticoagulants such as warfarin or heparin. Also should not be used in conjunction with anticonvulsant drugs used by epileptics, such as carbamazepine, phenytoin and phenobarbital, or with tricyclic antidepressants.

* Ginseng: Should not be used with warfarin, heparin, aspirin and other nonsteroidal anti-inflamatory drugs because it can inhibit clotting. Also may cause headache, tremulousness and manic episodes in patients treated with phenelzine sulfate. Should not be used with estrogens or corticosteroids because it may add to those drugs’ side effects. May also interfere with the heart drug digoxin or with digoxin monitoring. Should not be used by patients with diabetes because it can affect blood glucose levels.

* Karela: Should not be used by patients with diabetes because it can affect blood glucose levels.

* Kava: Should not be used with the tranquilizer alprazolam because it may result in coma.

* Kelp: May interfere with thyroid replacement therapies.

* Licorice: Can offset the effect of the diuretic drug spironolactone. May also interfere with heart drug digoxin or with digoxin monitoring.

* Saw palmetto: Avoid use with hormonal therapies such as estrogen replacement therapy and oral contraceptives because it may add to side effects. Tannic acid in herb may inhibit iron absorption.

* St. John’s wort: Can produce skin reactions to light, so fair-skinned users may wish to use caution and others taking drugs that cause light sensitivity, such as piroxicam or tetracycline, may want to avoid this herb. The active ingredient in St. John’s wort is uncertain, so it should not be used with two common types of psychiatric drugs called monoamine oxidase inhibitors and selective serotonin re-uptake inhibitors. Tannic acid in the herb may inhibit absorption of iron.

* Valerian: Should not be used with barbiturates, such as thiopental and phenobarbital, because it can cause excessive sedation.

* Kyushin (dried toad venom), plantain, uzara root and hawthorn: May interfere with heart drug digoxin or with digoxin monitoring.

* Shankapulshpi: Should not be used when taking the anti-seizure drug phenytoin because it may decrease the drug’s effectiveness.

Source: Lucinda G. Miller, Texas Tech University Health Sciences Center, Department of Pharmacy Practice; Archives of Internal Medicine, Nov. 9, 1998.