Herb/Drug Interactions
There has been a lot of media interest lately about the potential for herb-drug interactions. More and more people who are taking prescription drugs are using herbs as well setting up at least the potential for problems to occur. The incidence of herb-drug interactions is small when compared to the problem of drug-drug interactions but it is advisable to be aware of the potential anytime you consider taking an herbal remedy. It is especially important to let your doctor know if you are scheduling surgery as many of the drugs used in surgical procedures can be affected by herbals.
Some herbs will modify absorption of drugs when mixed together in the stomach and intestines. This may either increase or decrease absorption of drugs which could make the drugs toxic or ineffective. Aloe gel, Marshmallow root, Psyllium seed husks and Slippery elm are high in fiber that can impair drug absorption. Black walnut hull, Horse chestnut, Raspberry leaves, Tea and White willow contain tannins that may cause some drugs to precipitate and make then unabsorbable.
Bladderwrack, Kelp, and other seaweeds are high in iodine which can cause the same problem as tannins. Black pepper, Cayenne and Ginger are pungent herbs which are known to enhance the absorption of many drugs. To avoid problems with any of these herbs take them at least 1 hour before or 2 hours after drug dosing.
Some herbs may potentiate drugs being taken for cardiac problems. Lily of the Valley, Pleurisy root, and Scotch broom contain cardiac glycosides which have the same action as digoxin and should not be taken together. Butternut, Cascara sagrada, Rhubarb root, Senna and Yellow dock are strong cathartic laxatives that may alter heart rate. Coffee, Guarana, Horsetail, Licorice root, and Tea enhance urinary excretion of potassium the loss of which can exacerbate a heart problem.
Another group of herbs could potentiate sedative or tranquilizing drugs. These herbs include Black cohosh, California poppy, Hops, Kava, Motherwort, Skullcap, St John's wort, and Valerian.
If you are a diabetic you should be aware of herbs that can modify blood sugar levels. Aloe vera, Bilberry, Burdock root, Fenugreek, Garlic, Ginseng, Olive leaf, and Psyllium seed are known to lower blood sugar levels. Then there are those herbs that can increase blood sugar levels including Coffee, Guarana, Ma huang (Ephedra), Rosemary and Tea.
One type of interaction potential that can be a problem especially during surgical procedures are those herbs that can modify effects of anticoagulants. Cayenne, Garlic, Ginger, Ginkgo, and Turmeric are blood platelet aggregation inhibitors. Aggregation of platelets is one of the first steps in the process of blood coagulation. Some herbs and vegetables are high in vitamin K. Vitamin K can counteract the effects of anticoagulants. These plants include Alfalfa, Beets, Broccoli, Parsley, and Stinging nettles.
Many people are now taking prescription and over-the-counter drugs that reduce stomach acid production (Zantac, Axid, Prilosec, Tagamet). Herbs that are stomach acid-secretion stimulants could counteract these drugs. These include Cayenne, Cinnamon, Coffee, Dandelion, Devil's claw, Ginger, Goldenseal. and Yarrow.
Finally, the herb receiving the most attention lately is St John's wort. There have been quite a few reports of dramatically decreased blood levels of certain drugs when taken at the same time as St John's wort. The herb increases activity of an enzyme system responsible for detoxification (metabolism) of some drugs in the liver. The drug Cyclosporine is used to prevent rejection of implanted organs. Blood levels of this drug have been reduced by 40-60% when St John's wort is used. Indanivir is a drug used to treat AIDS. Some AIDS patients may also use St John's wort for its (weak) antiviral activity. In these patients blood levels of Indanivir have dropped dramatically. Other drugs whose metabolism may be increased are Carbamazepine, Corticosteroids, Erythromycin, Lidocaine, Lovastatin, Methadone, Nifedipine, and Quinidine. Some hormones are also affected by this increased enzyme activity. They include Estradiol, Estriol, Testosterone, and Cortisol.
Most herbs can be used safely with drugs. But it is always a good idea to check with a knowledgeable source about potential interactions, especially if you are taking drugs in one of the above categories.
Herb-Drug Interactions
Aloe vera
Aloe may alter gastrointestinal absorption of some drugs by causing shorter GI transit time. It is advisable to separate administration from other medication.
Dried, powdered aloe leaf:
Cardiac glycosides: Theoretically, overuse of aloe increases the risk of adverse effects from the cardiac glycosides, such as digoxin.
Antiarrhythmic drugs: Overuse of aloe can increase risk of drug toxocity.
Diuretics: Overuse of aloe can compound potassium loss.
Corticosteroids: Overuse of aloe can compound potassium loss.
Aloe gel:
Diabetes therapy: Diabetic patients using aloe products should have their blood sugars monitored closely due to the possibility of aloe having hypoglycemic effects.
Hydrocortisone: Theoretically, concomitant topical usemight increase anti-inflammatory effects.
Black Cohosh
Antihypertensives: A 1962 study (Genazzani, et al; Nature, 194(5), 544-545, 1962) isolated the chemical actein which was shown to have a hypotensive effect in rabbits and cats. Patients taking medication to control blood pressure should be cautioned about the concomitant use of black cohosh because of the potential for an additive hypotensive effect.
Cayenne
MAOIs, Antihypertensive drugs: Theoretically, cayenne can interfere with activity of these drugs by increasing catecholamine secretion.
Hepatically metabolized drugs: Theoretically, cayenne can increase metabolism ofdrugs by increasing glucose-6-phosphate dehydrogenase and adipose lipase activity.
Barbiturates and other sedative drugs: Theoretically, concomitant use can cause additive effects and side effects.
ACE inhibitors: Topically applied capsaicin might be involved with contributing to the cough reflex in patients using an ACE inhibitor.
Theophylline: Theoretically, using cayenne before or at the same time as theophylline might enhance theophylline absorption and blood levels.
Aspirin: Powdered chili taken thirty minutes before aspirin might reduce gastric mucosal damage.
Acid-inhibiting drugs: Theoretically, due to claims that cayenne increases stomach acid, it might interfere with antacids, sucralfate, H-2 antagonists, or proton-pump inhibitors.
Anticoagulants: Some animal studies have shown cayenne to have a fibrinolytic action which may potentiate anticoagulant drugs.
Chamomile
Anticoagulants: Chamomile contains small amounts of coumarin (in the range 0.000002% - 0.00002%). Theoretically, caution should be used in patients using anticoagulant therapy.
Benzodiazepines; Theoretically, concomitant use with benzodiazepines might cause additive effects and side effects.
Ethyl alcohol: Theoretically, liquid extract of chamomile might help prevent ulcer formation caused by ethyl alcohol.
Indomethacin: Theoretically, bisabolol, a constituent of the volatile oil in chamomile, might prevent ulcer formation caused by indomethacin.
Drugs with sedative properties: Theoretically, concomitant use with drugs with sedative properties can cause additive effects and side effects.
Echinacea
Immunosupressive drugs: Theoretically, echinacea may interfere with immunosupressant therapy.
Econazole nitrate: Concomitant use of echinacea and topical econazole can decrease the recurrence rate of vaginal candida infections.
Ephedra
Amitryptyline: Can block the hypertensive effects of ephedrine.
Dexamethasone: Ephedrine increases the clearance and reduces effectiveness of dexamethasone.
Diabetes therapy: Monitor blood glucose levels closely as ephedrine has a hyperglycimic effect and is a peripheral vasoconstrictor.
Digitalis: Theoretically, can cause cardiac arrhythmias.
MAOIs: Ephedrine can induce toxicity with MAOIs including tranylcypromine, selegiline, phenelzine and moclobemide. Can cause hypertension.
Methylxanthines: Theoretically, concomitant use of caffeine or theophylline can increase the stimulatory and adverse effects. Can also enhance thermogenesis and weight loss.
Oxytocin: Concomitant use with ephedra can cause hypertension.
Reserpine: Indirect sympathomimetic effects of ephedrine such as mydriasis and hypertension are antagonized by reserpine.
Urinary acidifiers such as ammonium chloride can increase ephedrine excretion.
Uirinary alkalinizers such as sodium bicarbonate can slow ephedrine excretion.
Feverfew
Anticoagulants, antiplatelet drugs: Feverfew inhibits platelet aggregation and secretion so it theoretically may potentiate anticoagulants.
NSAIDs: Theoretically can decrease the effectiveness of feverfew.
Garlic
Warfarin: Since garlic can cause alteration of platelet function, it may potentiate the action of warfarin and other anticoagulants.
Insulin: Insulin dose may require adjustment due to possible hypoglycemin effects of garlic.
Hypoglycemic drugs: Theoretically, garlic might increase effects and adverse effects of oral hypoglycemic drugs.
Ginger
Acid-inhibiting drugs: Theoretically, due to claims that ginger increases stomach acid, it might interfere with antacids, sucralfate, H-2 antagonists, or proton-pump inhibitors.
Anticoagulants, antiplatelet drugs: Theoretically, excessive amounts of ginger might increase the effect or the risk of bleeding.
Barbiturates: Theoretically, ginger may enhance barbiturate effects.
Antihypertensives: Theoretically, due to purported hypertensive or hypotensive effects, ginger might interfere with blood pressure therapy.
Cyclophosphamide: Theoretically, cyclophoshamide-induced vomiting might be prevented by prior administration of ginger.
Cardiac drugs: Theoretically, due to purported inotropic effect, ginger can interfere with cardiac drug therapy.
Diabetes drugs: Theoretically, due to purported hypoglycemic effect, ginger might interfere with diabetes therapy.
Ginkgo
Insulin: May raise blood glucose levels enough to alter insulin requirements in diabetics.
Anticoagulants: Due to the presence of blood serum platelet aggregation inhibitors, GBE may potentiate the effect of anticoagulants. In a recent case, a 70-year old male had been taking aspirin (one 325 mg tablet daily) for three years following coronary bypass surgery. He began taking two 40 mg tablets of GBE (50:1 extract), and one week later exhibited blurred vision with a red streak visible inside the eye. The patient had no previous history of eye disorders or recent eye trauma. The patient stopped taking the GBE, but continued to take the aspirin. No bleeding recurred over a three month follow-up period (Rosenblatt,et al,New Engl J Med, 336;15:1108,1997).
MAOI: Theoretically may potentiate monoamine oxidase inhibitors (such as tranylcypromine).
Papaverine: May potentiate papaverine intracavernosal injection for impotence.
Cyclosporin: Theoretically, ginkgo may prevent cyclosporin-induced nephrotoxicity.
Thiazide diuretics: Ginkgo can increase blood pressure used concomitantly with a thiazide diuretic.
SSRIs: GBE can reverse fluoxetine or sertraline-induced sexual dysfunction
Ginseng
Antipsychotic drugs: Theoretically, American ginseng can interfere with antipsychotic drugs.
Hormones: Theoretically, it can interfere with hormone therapy.
MAO inhibitors: There is one case report of insomnia, headache and tremors with concomitant phenylzine and ginseng. There is also one case report of hypomania with phenylzine and ginseng.
Stimulant drugs: Theoretically, concomitant use of ginseng can potentiate the activity of stimulant drugs. One study of caffeine used with 3 grams daily average of ginseng found a 1 in 6 chance of hypertension.
Warfarin: Theoretically, ginseng may potentiate anticoagulant therapy. There is one case report of a decreased international normalization ratio (INR) associated with the addition of Panax ginseng to warfarin therapy
Goldenseal
Acid-inhibiting drugs: Theoretically, due to claims that goldenseal increases stomach acid, it might interfere with antacids, sucralfate, H-2 antagonists, or proton-pump inhibitors.
Barbiturates: Theoretically, goldenseal might potentiate barbiturate-induced sleep time.
Antihypertensives: Theoretically, large amounts of goldenseal might interfere with blood pressure control due to vasoconstrictive action of the constituent hydrastine.
Heparin: Theoretically, goldenseal can inhibit anticoagulant effects due to the constituent berberine.
Drugs with sedative properties: Theoretically, concomitant use with drugs with sedative properties might cause additive effects and side effects.
Hawthorn
Digoxin: Hawthorn might have a synergistic effect with digoxin requiring a dosage adjustment if used concurrently.
Coronary vasodilators: Using hawthorn with theophylline, caffeine, papaverine, sodium nitrate, adenosine, epinephrine and other coronary vasodilators might cause additive vasodilatory effects.
Cardiovascular drugs: Hawthorn might potentiate or interfere with conventional drug therapy for heart failure, hypertension, angina, and arrhythmias
CNS depressants: Concomitant use of hawthorn and CNS depressants might have additive effects.
Kava
CNS depressants: May potentiate action of alcohol, barbiturates or other psychoactive pharmaceuticals. A recent case was reported in the summer 1997 issue of Medical Herbalism in which a patient was admited in a lethargic and disoriented state, possibly due to an interaction between kava and the drug alprazolam (Xanax). The patient was also taking cimetidine which is known to reduce hepatic clearance of alprazolam and increase circulating levels of the drug.
Levodopa: One report of concomitant use associated with reduced efficacy of levodopa, possibly due to dopamine antagonism
Licorice
Antihypertensive drugs: Theoretically, sodium and water retention due to licorice might diminsh the effect of antihypertensive therapy.
Aspirin: Theoretically, concomitant use might reduce damage to the gastrointestinal mucosa.
Corticosteroids: Concomitant use might potentiate the duration of activity of drugs such as hydrocortisone and triamcinolone.
Cardiac glycosides: Large doses of licorice during digoxin therapy can cause potassium loss, increasing the risk of cardiac toxicity.
Cimetidine: Theoretically, concomitant use might provide additive gastrointestinal protection from ulcerative damage.
Diuretics: Licorice may potentiate potassium loss effects of thiazide diuretics.
Hormones: Theoretically, licorice might interfere with estrogen or anti-estrogen therapy due to estrogenic and anti-estrogenic effects.
Insulin: May be synergistic with licorice extract glycyrhhizin in causing hypokalemia and sodium retention.
NSAIDs: Theoretically, concomitant use can compound NSAID sodium and water retention.
Milk thistle
Aspirin: Theoretically, altered aspirin metabolism in individuals with liver cirrhosis might be improved with concomitant use of milk thistle.
Hepatotoxic drugs: Silymarin can help prevent liver damage caused by drugs, including butyrophenones, phenothiazines, phenytoin, acetominophen, alcohol, and halothane.
Cisplatin: Theoretically, concomitant administration of the constituent, silibinin, might help prevent kidney damage.
Saw palmetto
Oral contraceptives, hormonal therapy: Concomitant use with saw palmetto can interfere with oral contraceptives and hormone therapy.
St John's wort
Antidepressants: Until the mechanism of action is completely elucidated, caution should be used when hypericum is used in conjunction with other psychoactive medications. Patients should be monitored for any side effects.
Birth control pills: St John's wort induces p450 microsomal enzyme system in liver which is responsible for clearing estrogen from system. Theoretically, this could reduce effectiveness of birth control pills.
Cyclosporin: St. John's wort induces p450 microsomal enzyme system in liver lowering cyclosporin levels by 50-70% within 2 weeks.
Indinavir: St. John's wort induces p450 microsomal enzyme system in liver lowering blood levels of indinavir by 60-80% rendering it therapeutically ineffective.
SSRIs: Concomitant use of St. John's wort is contraindicted because it can increase the risk of serotonin syndrome. There is one case report of serotonism (headache, sweating, dizziness and agitation) when used concurrently with paroxetine.
MAO inhibitors: Due to the uncertainty of MAO inhibition, foods and medications known to interact with MAO inhibitors should be avoided as a safety measure. These include tyramine containing foods such as aged cheeses, wines, pickled herring and medications such as levodopa.
Ephedrine alkaloids: Reports of postsurgical hypotensive crises with patients taking "natural" diet products containing high levels of ephedrine alkaloids concomitantly with St. John's wort. Thoought to be due to depletion of epinephrine and norepinephrine.
Meperidine: Reports of postsurgical hypertensive crises in patients taking St. Johns wort and administered meperidine during surgery.
Valerian
Alcohol: Theoretically, valerian can potentiate the effects of alcohol.
Barbiturates: Theoretically, concomitant use of valerian with barbiturates can cause additive therapeutic and adverse effects.
Benzodiazepines: Theoretically, concomitant use with benzodiazepines can cause additive therapeutic and adverse effects. Due to affinity of valerian extracts and valepotriates with GABA and benzodiazepine receptor sites (in vitro) and diminshment of diazepam withdrawal effects caused by sufficiently large doses of valepotriates (in rat models), valerian may be helpful in withdrawal from benzodiazepine drugs
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