Introduction to Antidepressants

Using Antidepressants

Effects of Antidepressants

Most antidepressants have a delayed onset of action, and can take anywhere from 4-6 weeks to cause any noticeable improvements.There are 3 main types of antidepressants that are commonly prescribed and their effects vary from one type to the other.

Classes of Antidepressants

SSRI

SSRI stands for Selective Serotonin Reuptake Inhibitor and include drugs like Fluoxetine (Prozac) and Paroxetine (Paxil). They work by increasing the amount of serotonin in the synapse, by decreasing the amount that is re-uptaken or "recicled" back to the presynaptic neuron.Thus, the amount of available serotonin is increased.

SSRI's are commonly used as the first line treatment for depression since they have a low toxicity and a favorable side-effect profile.Work done in 2005 by Dr. Jeffrey R. Lacasse and Dr. Johnathan Leo at the Florida State University College of Social Work, calls into question the link between serotonin deficiency and symptoms of depression, noting that the efficacy of SSRIs as treatment does not in itself prove the link, also describing concerns about the psychological effect of oversimplified, pseudo-scientific anti-depressant advertising on the public.(1).

SNRI

SNRI stands for Serotonin-norepinephrine Reuptake Inhibitor and includes drugs such as Duloxetine (Cymbalta), Venlafaxine (Effexor XR) and Desvenlafaxine (Pristiq). SNRI's are slightly different to SSRI's in that they aim to balance the levels of both serotonin and norepinephrine in the neuron.

Tricyclic Antidepressants

These include amytriptilline, comipramine and Desipramine and are the second oldest type of antidepressants. They are now rarely prescribed in favor of safer, more selective drugs, although they are still used because of their effectiveness, specially in severe cases of major depression. They work by blocking the reuptake of neurotransmitters such as serotonin and norepinephrine and have a wide range of side-effects including increased heart rate, drowsiness, dry mouth, constipation, urinary retention, blurred vision, dizziness, confusion, and sexual dysfunction.

They are also usually lethal in overdose, and have a narrow therapeutic window, with aproxiamtely 10 times the normal dose causing toxicity.

Monoamine Oxidase Inhibitors

This group includes drugs like Isocarboxazid (Marplan), Moclobemide (Aurorix) and Phenelzine (Nardil).They work by inhibiting the enzyme monoamine oxidase, which metabolizes neurotransmitters involved in depression, such as dopamine, serotonin and norepinephrine.

MAOIs are rarely prescribed anymore due to their dangerous interactions with certain foods and drugs, although a new generation of MAOIs has been introduced; moclobemide (Manerix), known as a reversible inhibitor of monoamine oxidase A (RIMA), which is as effective as SSRIs and tricyclic antidepressants, in depressive disorders, and does not require a special diet.

Combinations with Antidepressants

The combination of serotonergic antidepressants such as SSRIs with drugs affecting serotonin such as MDMA, tryptamines, triptans, MAOIs, etc. can lead to a condition known as Serotonin Syndrome which can be potentially life threatening and is contradicted in all accounts.

History of Antidepressants

Antidepressants

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References