• Using your textbooks, draw up a classification of the drugs that are used as antidepressants.

SSRIs: Fluoxetine, Citalopram, Escitalopram, Paraxetine, Sertraline

SNRIs: Duloxetine, Venlafaxine, Levomilancipran

TCAs: Imipramine and many others

5HT Receptor Modulator: Nefazodone, Trazadone, Vortioxetine

Tetracyclics, Unicyclics: Bupropion, Amoxapine, Maprotiline, Mirtazapine

Monoamine Oxidase Inhibitors: Phenelzine, Tranylcypromine, Selegiline

• What do the existing drugs all have in common regarding their mechanisms of action?

The existing drugs all have an effect on the Serotonin neurotransmitter by blocking 5HT receptors or SERT.

• How long does it take for the antidepressive effects of these drugs to appear? What is the reason for this?

Effectivity of antidepressants takes 6-8 weeks to be seen. This is because to have an effect on Serotonin receptors takes time. As the 5HT receptors will be desensitized or they will be reduced.

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

TAD:

Efficacy:  Drug titrated to minimum effective dose

Side effects: anticholinergic, alpha blocking effects, sedation, weight gain, arrhythmias and seizures in overdose

Safety: Seizures can occur as a result of overdose, lethal ventricular arrhythmias and fibrillation. Commonly used in suicide attempts. 

SSRIs:

Efficacy: Initial dose can be administered fully.

Side effects:  Sexual dysfunction, insomnia, headaches, nausea, diarrhoea, insomnia, hypersomnia, weight gain

Safety: Uncommon fatalities occur with overdose of SSRI alone.

• What is action of mirtazapine? 

Blocks alpha 2, increases NA and 5HT release; 5HT2A results in depressant effect, 5HT3 results in anxiolytic and decreases nausea; H1 and Alpha 1 has an indirect stimulation of 5HT1A which is anxiolytic.

• What is action of venlafaxine?

Moderate selective blockage of NET and SERT, more potent for 5HT than for NA. 

• What is the action of agomelatine?

MT1 and MT2 receptor agonist , also 5HT2C antagonist with antidepressant properties. 

Katzung B.G. et al. 2019. Pharmacology examination & board review. United States of America. Cenveo Publisher Services.