Q: In a past column you mentioned the dangers of combining drugs that cause drowsiness or sedation with herbs that cause the same effect, such as kava and valerian. Could you provide a list of these drugs and herbs?

A: What you refer to might be called an "add-on" interaction. It occurs when you combine agents that cause a similar side effect, in this case drowsiness or sedation. "Add-on" means that the effect is increased significantly beyond that of any one agent alone.

Such interactions are potentially the most common type of drug-to-drug interaction, since drugs causing such depressant effects are widely used and some are available in nonprescription products.

The result can be excessive drowsiness, dizziness and loss of muscle coordination, making it hazardous to drive or engage in other activities requiring complete alertness. In severe cases, there may be failure of blood circulation and breathing functions causing coma and death. For this reason, add-on depressant interactions can be among the most dangerous.

Just as the effects of sedative drugs can add to each other, herbs with depressant or sedative properties can add to the effects of depressant drugs.

Kava and valerian, used for anxiety and insomnia, are two such herbal supplements.

Following is an updated list of other herbal supplements that may produce drowsiness or sedation:

Apricot, Arnica, ashwagandha root, Baikal skullcap, black nightshade, black root, bupleurum, calamus, calendula, California poppy, capsicum, catnip, celery, couch grass, elecampane, German chamomile, goldenseal, gotu kola, hemlock, hops, Indian snakeroot, Jamaican dogwood, lady's slipper, lemon balm, passionflower, peyote, sage, sassafras, shepherd's purse, Siberian ginseng, skullcap, St. John's wort, stinging nettle, wild carrot, wild lettuce, withania, yerba mansa.

Be aware of potentially dangerous add-on interactions when you combine these herbs with drugs in any of the following depressant drug classes. (Only a few representative drugs are listed in each class, so ask your pharmacist about any other medications you might wish to know about.)

Alcohol: beer, liquor, wine, etc.

Anti-anxiety agents: alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan).

Anti-cholinergics: atropine (Donnatal), benztropine (Cogentin), dicyclomine (Bentyl), trihexyphenidyl HCl (Artane).

Anti-convulsant agents: carbamazepine (Tegretol), phenytoin (Dilantin), valproic acid (Depakene).

Anti-depressants: amitriptyline (Elavil), paroxetine (Paxil), trazodone (Desyrel).

Antihistamines: chlorpheniramine (Chlor-Trimeton) diphenhydramine (Benadryl), hydroxyzine (Atarax, Vistaril).

Anti-hypertensive agents (certain types): clonidine (Catapres), methyldopa (Aldomet), terazosin (Hytrin)

Antipsychotic Agents: chlorpromazine (Thorazine), haloperidol (Haldol), olanzapine (Zyprexa), risperidone (Risperdal).

Muscle relaxants: baclofen (Lioresal), cyclobenzaprine (Flexeril), methocarbamol (Robaxin, Robaxisal).

Narcotic analgesics: codeine (Tylenol with codeine), meperidine (Demerol), propoxyphene (Darvocet-N).

Sedative/hypnotics: flurazepam (Dalmane), temazepam (Restoril), triazolam (Halcion); nonprescription sleep aids, which contain antihistamines such as diphenhydramine or doxylamine, include Aspirin Free Anacin P.M., Compoz, Dormin, Excedrine P.M., Extra Strength Tylenol PM, Midol PM, Miles Nervine, Nighttime Pamprin, Nytol, Sleep-eze, Sominex, and Unisom.

From Healthy.net