The absence of adequate scientific data on the adverse interactions the herbal health supplements have with drugs and food could prove harmful to the Indian consumer. If international data is any indication, most of the products tested have some reaction or other when in contact with drugs or food.

The data brought out by CMP Medica, New Zealand shows that anthraquinone laxatives on interaction with digoxin and other cardioactive glycosides caused potassium depletion leading to increased risk of cardiac toxicity. Similarly, cola and caffeine when consumed under cardiac conditions and medications can cause cardio activity and/or hypertensive activity. Again, caffeine (in cola, ifex and paulinia) preparations when interacted with pipemidic acid, ciprofloxacin or enoxacin can cause antibacterial action of the quinolones to inhibit the metabolism of caffeine. Adverse effects of caffeine (tremor, tachycardia) may occur.

The CMP data identified 12 different conditions where St John's Wort, a major herbal ingredient, can cause adverse reactions in the body. The interactions and the possible reactions are: HIV protease inhibitors (reduced blood levels with possible loss of HIV suppression), immunosuppressants (reduced blood levels with transplant rejection), HIV non-nucleoside inhibitors (reduced blood levels with possible loss of HIV suppression), Anticonvulsants (reduced blood levels with risk of seizures theoretically possible), digoxin (reduced blood levels with theoretical loss of control of heart rhythm or heart failure), SSRIs and related antidepressants (increased serotonergic effects theoretically possible), Amitriptyline (reduced AUC), triptans (increased serotonergic effects with theoretical chances of adverse reactions), oral contraceptives (breakthrough bleeding, contraceptive failure also possible).

In the case of Ginseng (panax ginseng), the agency has done an exhaustive study and recorded its interaction with other drugs, disease conditions and foods. Here, if Ginseng interacts with cardiac conditions and medications such as digoxin the result is cardioactivity, hypotensive and hypertensive activity. Interference with pharmacodynamics and drug level monitoring is also there. Anticoagulants (possible potentiation), Insulin, Sulphonylureas, biguanides (possible potentiation of hypoglycaemic effects), CNS stimulants, MAOIs (potentiation of stimulation, potentiation of MAO inhibition (suspected pheneizin interaction), Oestrogens (mild potentiation theoretically possible), Corticosteroids (additive effects) and sidenafil (possible potentiation) were the other cases where such interactions were found.

Health supplements containing Guar Gum, if taken with antibiotics is likely to result in reduced gastrointestinal absorption. The study notes that gymnema sylvestre taken together with hypoglycaemic drugs including insulin can cause possible potentiation of hypoglycaemic effects.

The study also pointed out that passion flower, if taken along with sedative drugs (eg benzodiazepines, clonidine, opioid analgesics, henobarbitone) can potentiate sedative effects.