Antidepressant drugs: same effectiveness, different side effects

The question of which anti-depressant drug is most effective is irrelevant to the RAND study's conclusion (see "Treatment of Depression," page 1), according to coauthor, Kenneth B. Wells, M.D. "Our study began just as the new antidepressants [e.g., Prozac] began to come on market in 1988, and, by the end, about 25% of study participants were on them [either Prozac or newer, chemically similar, drugs like Paxil and Zoloft], but their efficacy is no greater than that of older antidepressants," said Dr. Wells. "The only difference is the side effect profile and the greater willingness of patients to take the newer drugs."

Older drugs, such as the tricyclic antidepressants (e.g., amitriptyline whose brand names include: Elavil, Tofranil), cause side effects like drowsiness, weight gain, blurred vision, dry mouth, constipation, and impaired urination.

But, unlike the side effects of Prozac which tend to diminish with time, those of the older antidepressants usually continue at the same rate, even with extended use. Prozac's side effects are nervousness, anxiety, sexual dysfunction [particularly delayed or absent orgasm], insomnia, tremor, drowsiness, fatigue, and gastrointestinal symptoms like nausea and diarrhea.

Another class of older antidepressants, the monoamine oxidase inhibitors (MAOIs), such as Nardil, Parnate, and Marplan, requires great care on the part of the user. MAOIs interact adversely with such ordinary over-the-counter products as nose drops, foods like red wine and aged cheese, and other prescription drugs like Prozac. (Some doctors prescribe both an MAOI and Prozac which has caused fatal interactions, according to the FDA.)

The newer drugs do not appear to have the potential for serious side effects like liver toxicity as the older antidepressants do and therefore do not require the same monitoring. The biggest concern regarding the newer drugs is the unknown. The 1995 Physicians' Desk Reference states, "The effectiveness of Prozac in long-term use, that is, for more than five to six weeks has not been systematically evaluated in controlled trials. Therefore, the physician who elects to use Prozac for extended periods should periodically reevaluate the long-term usefulness of the drug for the individual patient."

The new antidepressants are all under patent, whereas the older drugs are not. This means that only the latter are available generically at a much reduced price. Prozac, for example, is more than 12 times the cost of Elavil (amitriptyline).