Classification of drugs used as antidepressants:

8 Classes:

1. Tricyclic anti-depressants.
2. Mono-amine oxidase inhibitors
3. Serotonin Noradrenaline Reuptake inhibitors
4. Selective serotonin reuptake inhibitors.
5. Selective Noradrenaline reuptake inhibitors.
6. Serotonin Modulators
7. Tetracyclic and Unicyclic Anti-depressants
8. Circadian Rhythm regulators

Tricyclic anti-depressants

There are 2 categories:

Tertiary Amines (More 5-HT selective) and Secondary Amines (More NE selective).

Tertiary

• Amitriptyline, Butriptyline, imipramine, trimipramine, chlorimipramine Dothiepine.

Secondary

• Desimipramine, Nortriptyline, Amoxapine, Lofepramine.

Mono-amine oxidase inhibitors

Rasageline, Selegiline (Deprenil) = Selective MAO-B inhibitor.

Moclobemide – Selective MAO-A inhibitor (cheese reaction).

Tranylcypromine – Non selective MOA-A/B inhibitor (cheese reaction).

Serotonin Noradrenaline Reuptake inhibitors

More selective for 5-HT than NE.

Venlafaxine, Duloxetine.

Selective Serotonin Reuptake Inhibitors.

Fluoxetine, Paroxetine, Citalopram, Escitalopram, Sertraline, Fluvoxamine.

Selective Noradrenaline Reuptake inhibitor

Roboxetine

Serotonin modulators

Trazadone, Vortioxetine.   

Tetracyclic and Unicyclic AD’s

Mianserin, Mirtazepine, Bupropione (Unicyclic).

Circadian Rhythm Regulators  

Agomelatine.

What do they all have in common?

They all have an effect on the Serotonin and Noradrenaline reuptake inhibitors or agonist/antagonist of serotonin. – They all increase/stimulate Serotonin and Noradrenaline effects.

How long does it take for the anti-depressive effects of these drugs to appear? What is the reason for this?

It takes 6-8 weeks before Anti-depressant effect is optimal. Researchers says that it may be due to other changes that occur as a reaction to the changed serotonin levels.

How do the TADs and the selective serotonin reuptake inhibitors (SSRI’s) differ in respect of:

Efficacy

TAC – Less effective, used as an alternative for MDD- patients unresponsive to commonly used AD’s.

SSRI’s – More effective, better side effect profile, safe in acute overdose, help patients lose weight.

Side effects

TAC – Sedation, tremors, insomnia, Anticholinergic effects, cardiovascular, hypotension, psychosis, convulsions. Weight gain.

SSRI’s – Insomnia, tremors, GIT disturbances, headache, decreased libido and sexual dysfunction. Extra pyramidal symptoms. Weight loss- decreased appetite.

Safety

TAC – More dangerous – Cardio toxic

SSRI’s – More Safe.

What is the action of mirtazapine?

Blocks NA auto receptors which increases NA, and blocks 5-HT. It stimulates the release of Na and serotonin. There is indirect stimulation of 5-HT1a and blocks 5-HT3 and 5-HT2. It also blocks H1 and a1 receptors.

What is the action of venlafaxine?

Blocks both 5-Ht and NA reuptake, it is more potent for 5-HT than Na. It has a low affinity for M, H1 and A1 receptors.

What is the action of agomelatine?

MT1,MT2, 5HT-2c antagonist.