It often takes two to four weeks for antidepressants to start having an effect and six to 12 weeks for antidepressants to have their full effect. The first antidepressant medications were introduced in the 1950s. Research has shown that imbalances in neurotrans- mitters like serotonin, dopamine and norepinephrine can be corrected with antidepressants. The FDA regularly approves different medicines; visit www.fda.gov for the most current list. Four groups of antidepressant medications are most often prescribed for depression:
• Selective serotonin reuptake inhibitors (SSRIs) act specifically on the neurotransmitter serotonin. They are the most common agents prescribed for depression worldwide. These agents block the reuptake of serotonin from the synapse to the nerve, thus artificially increasing the serotonin that is available in the synapse (this is functional serotonin, since it can become involved in signal transmission, the cardinal function of neurotransmitters). SSRIs include fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), escitalopram (Lexapro) and fluvoxamine (Luvox).
• Serotonin and norepinephrine reuptake inhibitors (SNRIs) are the second-most popular antidepressants worldwide. These agents block the reuptake of both serotonin and norepinephrine from the synapse into the nerve (thus increasing the amounts of these chemicals that can participate in signal transmission). SNRIs include venlafaxine (Effexor) and duloxetine (Cymbalta).
• Bupropion (Wellbutrin) is a very popular antidepressant medication classified as a norepinephrine-dopamine reuptake inhibitor (NDRI). It acts by blocking the reuptake of dopamine and norepinephrine.
• Mirtazapine (Remeron) works differently from the compounds discussed above. Mirtazapine targets specific serotonin and norepinephrine receptors in the brain, thus indirectly increasing the activity of several brain circuits.
• Tricyclic antidepressants (TCAs) are older agents seldom used now as first-line treatment. They work similarly to the SNRIs, but have other neurochemical properties which result in very high side effect rates, as compared to almost all other antidepressants. They are sometimes used in cases where other antidepressants have not worked. TCAs include amitriptyline (Elavil, Limbitrol), desipramine (Norpramin), doxepin (Sinequan), imipramine (Norpramin, Tofranil), nortriptyline (Pamelor, Aventyl) and protriptyline (Vivactil).
• Monoamine oxidase inhibitors (MAOIs) are also seldom used now. They work by inactivating enzymes in the brain which catabo- lize (chew up) serotonin, norepinephrine and dopamine from the synapse, thus increasing the levels of these chemicals in the brain. They can sometimes be effective for people who do not respond to other medications or who have “atypical” depression with marked anxiety, excessive sleeping, irritability, hypochondria or phobic characteristics. However, they are the least safe antidepressants to use, as they have important medication interactions and require adherence to a particular diet. MAOIs include phenelzine (Nardil), isocarboxazid (Marplan) and tranylcypromine sulfate (Parnate).
• Nonantidepressant adjunctive agents. Often psychiatrists will combine the antidepressants mentioned above with each other (we call this a “combination”) or with agents which are not antidepressants themselves (we call this “augmentation”). These latter agents can include the atypical antipsychotic agents [aripiprazole (Abilify), olanzapine (Zyprexa), quetiapine (Seroquel), ziprasi- done (Geodon), risperidone (Risperdal)], buspirone (Buspar), thyroid hormone (triiodothyonine or “T3”), the stimulants (methylphe- nidate (Ritalin), dextroaphetamine (Aderall)), dopamine receptor agonists (pramipexole (Mirapex), ropinirole (Requipp)), lithium, lamotrigine (Lamictal), s-adenosyl methionine (SAMe), pindolol and steroid hormones (testosterone, estrogen, DHEA).
Individuals living with mental illness and their families must be cautious during the early stages of medication treatment because normal energy levels and the ability to take action often return before mood improves. At this time—when decisions are easier to make, but depression is still severe—the risk of suicide may temporarily increase.