Antidepressant

As its name indicates, an antidepressant medicine is prescribed to treat depression. The French Health Products Agency (Afssaps) classifies these into four categories depending on their molecular structure and mechanism of action.

The different categories of antidepressants

• The tricyclics. These medicines inhibit re-uptake of several neurotransmitters (noradrenaline, serotonin, dopamine).
• The selected serotonin re-uptake inhibitors (SSRI) and serotonin and noradrenaline re-uptake inhibitors (S-NARI). As their name indicates, SSRI act only by inhibiting re-uptake of serotonin in the synapse. The S-NARI also act by inhibiting re-uptake of noradrenaline.
• The selective or unselective monoamine oxidase inhibitors (MOAI). This class of medicines prevents the action of two enzymes: type A monoamine oxidase (MOA A) and type B monoamine oxidase (MOA B). Both of these break down neurotransmitters.
• These antidepressants therefore have a different mechanism of action. The antidepressants which belong to this family do not a;; have the same mechanisms of action. They all act on synapses or neurones, increasing the levels of some neurotransmitters involved in depression.

Sources:

• French Health Products Safety Agency (Afssaps), subject-based file/antidepressant treatments, 28 February 2008
• Vidal 2010, Le Dictionnaire
• McGill University website (Montreal, Quebec Province), accessed on 25 May 2011