In general, antidepressants enhance the availability of naturally occurring chemicals called neurotransmitters to the brain and are categorized into groups based on the chemicals in the brain they affect. There are three types of antidepressants that block the action of the neurotransmitter, acetylcholine. One function of acetylcholine is to control the function of the gastrointestinal tract. Blocking acetylcholine reduces the production of mucus and saliva secretions causing dry mouth.
Selective Serotonin Reuptake Inhibitors (SSRIs)
The Mayo Clinic explains that selective serotonin reuptake inhibitors appear to relieve the symptoms of depression by blocking the reuptake of serotonin by certain nerve cells in the brain. These drugs are selective because they only target serotonin, a neurotransmitter associated with depression. This group includes citalopram which is used to treat major depressive disorders characterized by a depressed mood state that occurs nearly every day, lasts for two weeks and interferes with daily functioning. Fluoxetine, another SSRI, is widely used to treat major depressive disorders, obsessive-compulsive disorders, bulimia nervosa and panic disorders. Sertraline belongs to the group of SSRIs and is prescribed to treat major depressive disorders, obsessive-compulsive disorder, panic disorder and posttraumatic stress disorder. Two additional SSRIs are escitalopram and paroxetine. The SSRIs tend to have fewer side effects than other antidepressants.
Heterocyclic Antidepressants
This group of medications includes amitriptyline, desipramine, imipramine and nortriptyline Once the mainstay of treatment, these drugs are prescribed less frequently because overdose causes toxicity and they have more serious side effects than other antidepressants. They are tricyclic antidepressants used in the treatment of depression, some forms of anxiety, fibromyalgia and pain management. Short-term effect is to increase the availability of norepinephrine. Long-term effect is reduced control of specific receptors on membranes that transmits signals from one nerve cell to another.
Serotonin-Norepinephrine Reuptake Inhibitors
This class of antidepressants includes venlafaxine and duloxectine, which have the same mechanism of action as the tricyclic antidepressants and similar toxicity as the SSRIs. Venlafaxine is available as a extended-release tablet used to treat depression, generalized and social anxiety and pain disorders. In addition to its use as an antidepressant, duloxectine is indicated in the management of neuropathic pain associated with some cases of diabetes and in the treatment of fibromyalgia. Both drugs selectively inhibits the reabsorption of serotonin and norepinephrine.
