Antidepressants Medications

• Uses
• Classification
• How do antidepressants work
• Choosing the antidepressant
• Selective serotonin reuptake inhibitors
• Tricyclic antidepressants
• Serotonin and norepinephrine reuptake inhibitors
• Norepinephrine and Dopamine Reuptake Inhibitors
• Combined reuptake inhibitors and receptor blockers
• Noradrenergic and Specific Serotonergic Antidepressants
• Monoamine oxidase inhibitors

The history of antidepressants begins with the tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). Both of these classes of antidepressants were successful and were discovered by chance. The first antidepressants became available in the late 1950s.

Newer antidepressants such as the SSRIs have largely replaced older TCAs and MAOIs as first-line depression drugs. However, Tricyclic antidepressants and MAOIs remain valuable alternatives for patients with moderate to severe depression.

Antidepressant medications are primarily used in the treatment of depression. They are effective in about 60-70% of all patients with depression.

Antidepressants as a class of psychotropic medications have the following broad range of indications:

• major depressive disorder
• bipolar disorder
• psychotic disorders
• substance-induced mood disorders
• sleep disorders
• anxiety/panic disorders
• eating disorders
• pain syndromes
• irritable bowel syndrome
• enuresis
• cigarette addiction

There are many different types of antidepressant. Antidepressants are put into groups based on which chemicals in the brain they affect. Main classes of antidepressant include:

• Tricyclic antidepressants (serotonin and noradrenalin reuptake inhibition with effects on multiple receptor system and sodium conductance)
• Monoamine oxidase inhibitors (MAOIs)

• Selective serotonin reuptake inhibitors (SSRIs)
• Selective noradrenaline reuptake inhibitors (NARI)
• Serotonin and norepinephrine reuptake inhibitors (SNRIs)
• Norepinephrine and dopamine reuptake inhibitors (NDRIs)

• Noradrenergic and specific serotonergic antidepressants (NaSSA) (serotonin (5-HT2A and 2C, 5-HT3) receptor blockade with noradrenalin (alpha-2) receptor blockade)
• Serotonin (5-HT2A) receptor blockade with serotonin reuptake inhibition (nefazodone, trazodone)

Tricyclic antidepressants are one of the oldest classes of antidepressants. Now there are newer, more popular types, such as SNRI and NDRI. SSRIs and SNRIs have largely replaced the first generation of antidepressants, which are as effective but more likely to produce side effects.

All antidepressants work on the principle of enhancing one or more of the neurotransmitters in the brain. Neurotransmitters are molecules that specialize in delivering packets of information from one neuron to another.

Neurotransmitters cannot be taken orally or intravenously because they cannot pass the brain-blood barrier.

When choosing the antidepressant the important aspects are:

• safety, including possibility of overdosing or pregnancy
• previous response by patient or family member
• symptom profile or type of depression (anxious or retarded)
• side effect profile
• concurrent medication
• other medical illness
• age of patient (psychological therapies are usually the first choice for children and adolescents)
• patient’s compliance
• physician’s experience with antidepressant
• personal preferences

• Citalopram (Celexa)
• Escitalopram (Lexapro)
• Fluoxetine (Prozac)
• Paroxetine (Paxil)
• Sertraline (Zoloft)

Selective serotonin reuptake inhibitors act only on the neurotransmitter serotonin, while tricyclic antidepressants and MAO inhibitors act on both serotonin and another neurotransmitter, norepinephrine, and may also interact with other chemicals throughout the body. Selective serotonin reuptake inhibitors have fewer side effects than tricyclic antidepressants and MAO inhibitors. Some of the side effects that can be caused by SSRIs include dry mouth, nausea, nervousness, insomnia, headache and sexual problems.

• Amitriptyline (Elavil)
• Amoxapine
• Desipramine (Norpramin)
• Doxepin (Sinequan)
• Imipramine (Tofranil)
• Nortriptyline (Pamelor)
• Protriptyline (Vivactil)
• Trimipramine (Surmontil)

The tricyclics have been used to treat depression for a long time. They act on both serotonin and another neurotransmitter, norepinephrine, and may also interact with other chemicals throughout the body. Common side effects caused by these medicines include dry mouth, blurred vision, constipation, difficulty urinating, worsening of glaucoma, impaired thinking and tiredness.

• Venlafaxine (Effexor)
• Duloxetine (Cymbalta)

Serotonin and norepinephrine reuptake inhibitors works by slowing down the reuptake of both serotonin and noradrenaline, but more selectively than other drugs.

• Bupropion (Wellbutrin)

NDRIs block the reuptake of neurotransmitters norepinephrine and dopamine, increasing the levels of these neurotransmitters in the synapses.

• Trazodone (Desyrel)
• Nefazodone (Serzone)

Trazodone and nefazodone are phenylpiperazine antidepressants.

Trazodone is a serotonin reuptake inhibitor and is also a 5-HT2 receptor antagonist. This results in more serotonin to stimulate other nerves. This medication has sedative and antidepressant properties.

Nefazodone works by inhibiting the uptake by nerves of serotonin and norepinephrine. Nefazodone is chemically related to trazodone, and shares its actions. Nefazodone has a lesser risk of priapism.

• Mirtazapine (Remeron)

The novel antidepressant mirtazapine has dual mode of action. It is a noradrenergic and specific serotonergic antidepressant that enhances noradrenergic and serotonergic neurotransmission. Mirtazapine has been proved effective in the treatment of patients who were resistant or intolerant to SSRIs.

• Phenelzine (Nardil)
• Tranylcypromine (Parnate)
• Isocarboxazid (Marplan)
• Selegiline (Emsam)