Side Effects of Goldenseal

I just read your answer to a reader's question on the long term effects of echinacea and goldenseal. Although you did not mention goldenseal, that is my interest. My husband was taking goldenseal 3X a day for many months. How can I find out about side effects of herbs?
This is what was listed under goldenseal:
Precautions
Pregnant and breast-feeding women should not use this herb as it may stimulate uterine contraction. Patients with high blood pressure should also avoid goldenseal. The herb should be taken only for very limited periods, as it builds up in the mucosa of the system and its strong alkaloids are neurotoxic over an extended time (i.e., several months of daily use). Three weeks on and three weeks off is a good routine for dosage. Do not eat the plant fresh, as it can irritate mucous tissues.
Side effects
Goldenseal use can destroy organisms that are beneficial to the body, as well as those that are pathological. It should be used only for limited periods of time.
What organisms can goldenseal destroy?

Goldenseal is drying to the mucous membranes, so is useful in conditions of excess mucus of the mouth, throat, stomach, bowels and vagina. Goldenseal must come in contact with these mucous membranes to be useful. It is not well absorbed into the blood stream, so is not considered useful in systemic infections such as colds and influenza.
Because goldenseal is drying, high doses and long term use can cause dry, cracked and bleeding mucous membranes.
Goldenseal inhibits the bacteria Heliobacter pylori, considered to be a primary causative factor in stomach ulcers. Because goldenseal contains berberine, it may also be useful in destroying protazoal and fungal organisms that cause infections such as giardia and dysentery.
There isn't a single source that will give you accurate information on the side effects of all herbs. An excellent guide for uses and contraindications is Michael Moore's "Medicinal Plants of the Pacific West" (Red Crane Books, Santa Fe). Very conservative guides that are not written by herbalists include "Herbal Medicine", by Newall, Anderson and Phillips (Pharmaceutical Press, 1 Lambeth High Street, London SE1 7JN, England) and "The Complete German Commission E Monographs (publisher American Botanical Council), the official German guide to physicians' use of herbal remedies. These conservative lists of possible side effects and interactions are based on potential actions of herb constituents rather than interactions and side effects of herbs as experienced in use by herbalists. A good, general guide to the use of herbs as medicine is David Hoffman's "The Complete Illustrated Holistic Herbal".