Dear Dr. SerVaas: I read in your "Medical Mailbox" that a Brazilian research team has discovered that lithium taken by elderly people seemed to prevent the onset of Alzheimer's disease (Nov./Dec. '04).In the article, you mentioned that drug companies were working on lithium-like drugs that would produce this effect but would be free of the side effects sometimes noted with long-term lithium therapy.

Could you tell us what you consider to be the long-term side effects of lithium?

Dear Reader: "There are several side effects that may be troubling with long-term use of lithium," explains Dr. John Nurnberger.

"Hand tremor is noticeable for many people, and problematic for perhaps 10 percent. Weight gain may also be an issue--the average weight gain on lithium is about 5 pounds, but a small minority will gain 25 pounds or more. Decreased thyroid function is seen in about one-fourth of patients on lithium. While decreased kidney function is sometimes observed, it rarely would require stopping the medication. A small number of patients on lithium will experience memory difficulties. This may take the form of difficulty in finding the right word while speaking. Reducing the dose of lithium (if possible) is usually helpful.

"In general, it is wise to monitor lithium levels more carefully in the elderly and to consider using lower doses."

Dr. Nurnberger adds that the Brazilian study is interesting.

"There are data suggesting that lithium has a neuroprotective effect, and this would be compatible with that idea," he says.