While the MAOIs have fewer side effects than the tricyclic drugs, they can still cause problems in some individuals. Some common side effects include insomnia, impotence and other sexual dysfunction, dizziness, weight gain, and water retention. They can also produce a dangerous elevation in blood pressure, if the patient consumes substances containing the amino acid tyramine. These foods include all cheeses except cottage cheese and cream cheese, all forms of alcohol, pickled or smoked meats or fish, liver, sausage, salami, yeast, and fava beans. Persons taking MAOIs also need to watch their consumption of yogurt, sour cream, tomatoes, spinach, eggplant, avocado, soy sauce, raisins, plums, and bananas. Certain over-the-counter remedies, such as decongestants and antihistamines, must also be avoided. Needless to say, these restrictions put a crimp in most people's diets, so psychiatrists are less likely to prescribe them.

Because it was originally believed that St. John's wort worked through MAO inhibition, current sources on the herb still list the MAOI food restrictions. However, it is now quite clear that St. John's wort does not have this effect, and the warnings are unnecessary.

If the MAOIs and SSRIs are combined, there is the potential for a dangerous reaction known as the "serotonin syndrome". Therefore, it is essential that there be at least a two-week period when switching from a MAOI to a SSRI, and a five-week period when changing from a SSRI to a MAOI. SSRIs, particularly Prozac, remain in the body for an extended period.

The Selective Serotonin Re-Uptake Inhibitors
Prozac (fluoxetine hydrochloride) was the first selective serotonin re-uptake inhibitor, or SSRI, put on the market. First introduced in 1987, it quickly became the most widely prescribed antidepressant medication ever. In fact, sales of Prozac accounted for $1.2 billion in 1995, and over 6 million Americans use it regularly. Prozac's success has spawned other SSRIs, including Zoloft (sertraline hydrochloride) and Paxil (paroxetine hydrochloride).

How do these drugs work? In Chapter 3 of the book "The Mind, Body and Mental Health", we saw how neurons release a neurotransmitter called serotonin into the synapses between cells. The SSRIs desensitize a receptor on the neuron that would normally absorb serotonin into the cell. As a result, there is a greater supply of serotonin in the synapse, which allows the neurons to transmit a stronger serotonin signal. Serotonin is one of the brain's natural antidepressants, so higher serotonin levels enhance mood and bring about a reduction in depressive symptoms.

The introduction of the SSRIs was considered a major advance in the pharmaceutical treatment of depression. Prior to this time, the only synthetic drugs on the market were the tricyclic drugs and the MAOIs. These options all have a variety of side effects, and persons using the MAO inhibitors also have to follow a restricted diet. That is why the development of the SSRIs was seen as a significant breakthrough.

Developed by Eli Lilly and Company after fifteen years of clinical research, Prozac has been marketed as a highly effective solution for depressive symptoms. It has even been recommended in best-selling books as a way to develop a more "socially rewarding personality." Yet despite all the media attention, studies show that Prozac is no more effective than St. John's wort-or other antidepressant drugs, for that matter-in combating depression.