Chapter 18: Drugs Used in Mood Disorders

ORGANIZATION OF ANTIDEPRESSANTS

All of the antidepressant drugs increase the concentration of norepinephrine or serotonin in the synaptic cleft. In most cases, they do this by inhibiting the reuptake of the neurotransmitters. Remember that reuptake is the major route for termination of action of these neurotransmitters. Other drugs block their metabolic degradation or increase their release.

It is most logical to divide the antidepressants into five groups. Three groups are named according to their mechanism of action. Therefore, if you can remember the name of the group, you have already learned an important fact about each drug in the group. One group, the heterocyclics, consists mostly of tricyclic compounds (tricyclic antidepressants—TCA). They are grouped together mainly on the basis of structure, but they also have similar actions and side effects.

The trouble most students seem to have with these drugs is with their names. As you can see from the following table, the names of these drugs give no clues to their class. This is one instance where name recognition becomes very important for examination preparation. You may know everything about the monoamine oxidase (MAO) inhibitors, but if you do not recognize that tranylcypromine belongs to that group, you may not be able to answer a question about this drug.

Learn what you can about each class of antidepressant and then be sure that you know the names of the drugs in each class.

SEROTONIN-SPECIFIC REUPTAKE INHIBITORS

These drugs block the reuptake of serotonin, without affecting reuptake of norepinephrine or dopamine. Therefore, they are referred to as serotonin-specific reuptake inhibitors or selective serotonin reuptake inhibitors. Either name gives you the abbreviation SSRI. It is currently believed that the mechanism by which these drugs alleviate depression is by their blockade of the reuptake of serotonin. This may seem self-evident. It takes several weeks of treatment with SSRIs to achieve a full therapeutic effect and there is no evidence that one SSRI is more effective than any other.

The initial treatment of choice for most patients is an SSRI. Drugs in this class are effective in a wide range of disorders in addition to depression. SSRIs have efficacy in eating disorders, panic disorder, obsessive compulsive disorder, and borderline personality disorder.

SSRIs are essentially devoid of agonist or antagonist activity at any neurotransmitter receptor. Sexual dysfunction is a side effect of the drugs in this class. Severe withdrawal symptoms can occur if the SSRI is stopped abruptly.