Interactions between complementary medicines and conventional medicines

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We are often asked about complementary medicines and their safety. The following table has been prepared by Poole Primary Care Trust with the kind permission from West Lincolnshire PCT and Eastern Birmingham PCT - updated April 2004.

HERBAL MEDICINE	CONVENTIONAL DRUG	POTENTIAL INTERACTION
Betel Nut	Typical Antipsychotics	Rigidity, bradykinesia, tremor, stiffness, akathesia
Cat’s Claw	Benzodiazepines, calcium channel blockers, simvastatin, protease inhibitors	Inhibition of CYP3A4 (drug-metabolising enzyme), therefore potential for concentrations of drugs to increase in the body.
Chamomile	Sedatives	Additive effect i.e. cause more drowsiness
Chilli Pepper	ACE Inhibitor Theophylline	Cough Increased absorption and bioavailability
Coenzyme Q10	Warfarin	Structurally similar to vitamin K, this may reduce effectiveness of warfarin
Cranberry	Warfarin	Increased bleeding time
Danshen	Warfarin	Increased bleeding time
Devils Claw	Warfarin	Blood disorders visible on the skin (Purpura)
Dong Quai	Warfarin Quinolone antibiotics, St John’s Wort	Increased bleeding time and widespread bruising Increased risk of photosensitivity
Echinacea	Methotrexate Amiodarone Ketoconazole	Hepatotoxicty
Echinacea	See under Cat’s Claw Immunosuppressants Corticosteroids Cyclosporin	Antagonistic effect
Ephedra	Beta-blockers, general anaesthetics, MAOIs	Amphetamine-like side effects including elevated blood pressure and rapid heart beat
Evening Primrose Oil	Anticonvulsants	Lowered seizure threshold
Feverfew	NSAIDs e.g. ibuprofen Warfarin	Inhibition of herbal effects Altered bleeding time
Garlic	Warfarin Aspirin Hypoglycaemics	Altered bleeding time, inhibits platelet aggregation Garlic may lower blood glucose levels
Gingko	Warfarin Aspirin Thiazide Diuretics Sedatives	Altered bleeding time, inhibits platelet aggregation Hypertension
Ginseng	Warfarin Oestrogens, Corticosteroids MAOI’s Insulin, sulphonylureas, Biguanides Digoxin (Siberian Ginseng)	Altered bleeding time Additive effect Headache, manic episodes, tremulousness Altered glucose concentration, avoid concomitant use Interferes with drug level monitoring and raised digoxin levels
Glucosamine	Warfarin (when combined with chondroitin)	Altered bleeding time
Guar Gum	Sulphonylureas, Biguanides Penicillin V, Digoxin, Paracetamol, diuretics	Gastric Retention prolonged so absorption of many drugs is decreased
Karela	Chlorpropamide	Decreased blood glucose levels
Kelp	Thyroxine	Iodine content of kelp may interfere with thyroid replacement
Liquorice	Spironolactone Oral Contraceptives Systemic Corticosteroids	Antagonism of diuretic effect Hypertension, oedema, hypokalaemia Increases plasma concentrations of steroids
Papaya	Warfarin	Increased bleeding time
Psyllium	Lithium	Decreased lithium concentrations

Saw Palmetto	Iron Anticoagulant & antiplatelet therapies	May inhibit absorption May increase risk of bleeding
Saiboku-to (Asian Herbal Mixture)	Prednisolone	Increased effect of corticosteroid
Saiboku-to (Asian Herbal Mixture)	Prednisolone	Increased effect of corticosteroid
St John’s Wort	Anticonvulsants Ciclosporin Digoxin HIV Protease Inhibitors Oral contraceptives Antidepressants Theophylline & aminophylline Triptans Warfarin & phenindione Tamoxifen	St. John’s Wort induces some cytochrome P450 enzymes inducing the metabolism of the interacting drugs, giving lower blood concentrations and reduced effect. Break through bleeding can occur with the contraceptive pill.
Saiboku-to (Asian Herbal Mixture)	Prednisolone	Increased effect of corticosteroid
Shankhapushpi (Ayurevedic mixed-herb syrup)	Phenytoin	Decreased Phenytoin concentration, loss of seizure control
Sho-Saiko-to OR Xiao Chai hu tang (Asian herb mixture)	Prednisolone	Increased effect of corticosteroid
Tamarind	Aspirin	Increased bioavailability of aspirin
Valerian	Anxiolytics, hypnotics and any medicines that cause drowsiness Alcohol	Sedation and drowsiness may be increased when taken with valerian. Adverse effects on alcohol concentrations
Yohimbine	Tricyclic Antidepressants	Hypertension

Complementary Therapies and Conventional Medicines

Acupuncture – contraindicated in patients taking warfarin or with bleeding disorders

Aromatherapy

o Avoid deep massage near tumours

o Avoid leg massage in DVT

o Some oils may precipitate epileptic fits

o May cause sensitisation to sun

Chiropractic/Osteopathy

o Contraindicated in aneurism, acute fracture or dislocation

o Caution in osteoporosis

o Recent fracture or whiplash

o Rheumatoid arthritis

o Ankylosing spondolytis

Herbal remedies

o AVOID in patients taking drugs with a narrow therapeutic range or where drug therapy is critical.

o Insufficient evidence to recommend use in pregnancy and breastfeeding

Homeopathy

o Homeopathic remedies of dilution greater than 12c or 30x from reputable manufacturers are unlikely to cause adverse effects or interact with conventional therapies

o Some practitioners believe that conventional drugs may reduce the efficacy of homeopathy

THIS TABLE IS NOT INTENDED TO BE COMPREHENSIVE, BUT COVERS THE MORE COMMON HERB-DRUG INTERACTIONS

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Interactions between complementary medicines and conventional medicines

Betel Nut

Cat’s Claw

Chamomile

Chilli Pepper

Coenzyme Q10

Cranberry

Danshen

Devils Claw

Dong Quai

Echinacea

Psyllium

Saw Palmetto

Complementary Therapies and Conventional Medicines

Chiropractic/Osteopathy