Anti-depressants

Question 1

Classification of anti-depressants?

Answer 1

1. SSRI”s (Selective serotonin re-uptake inhibitors)
2. SNRI’s “5-HT” (Serotonin) and noradrenaline
3. TCA’s (Tri-cyclic anti-depressants) - with either “psychomotor” or “sedative” activity.

Question 2

Actions of SSRI’s?

Answer 2

They function to block the re uptake of serotonin and cause its accumulation in the synaptic cleft. 2 weeks to show significant improvements in mood and approximately 12 weeks to show full beneficial effect of drug.

Examples include : Fluoxentine, paroxentine, citalopram, escitalopram and fulvoxamine.

Question 3

SSRI’s Pharmacokinetics?

Answer 3

Good oral absorption, not affected by food. CYP-P450 metabolism or either by glucuronide / sulphate conjugation. Fluoxetine / paroxetine are potent CYP-2D6 inhibitors, hence affecting alternative drug reactions.

Question 4

SSRI adverse effects?

Answer 4

GI disorders (nausea, vomiting and diarrhoea), sleep disorders, sexual dysfunction, fatigue and headache. It can also lead to “discontinuation syndrome” and “Serotonin syndrome”.

Question 5

Therapeutic uses of SSRI’s ?

Answer 5

Depression, OCD, panic disorder and general anxiety disorders.

Question 6

Function of SNRI’s?

Answer 6

The functions of SNRI’s are to treat pains that are associated with depression such as “back aches” and “muscle aches”.

Question 7

Explain the types of “SNRI’s”?

Answer 7

“Venlafaxine” is a inhibitor of serotonin uptake, at high doses is an inhibitor of noradrenaline uptake. Hepatic metabolism of venalfaxine produces active metabolite “desvenlafaxine”. Nausea, dizziness and sexual dysfunction are some side effects.

Duloxentine is another SNRI which functions to inhibit serotonin/noradrenaline re uptake at any dose. Hepatic metabolism produces inactive metabolites.

Question 8

Actions of tetracyclines?

Answer 8

Function to block serotonin and norepinepherine uptake, improves mood in 50-70% of users. Examples include “Tertiary amines” such as amitryptyline, imipramine, clomipramine and “secondary amines” desipramine and nortriptylin.

Question 9

TCA therapeutic uses ?

Answer 9

Moderate to severe depression, in low doses used to treat insomnia and panic disorder.

Question 10

TCA adverse effects?

Answer 10

Due to blockage of alpha 1 and muscarinic receptors. Muscarinic receptor blockage leads to anti-cholinergic effects such as xerostomia, constipation, urinary retention, sinus tachycardia, nausea and blurred vision.

Blockage of alpha 1 receptors by TCA causes : orthostatic hypertension, reflex tachycardia and dizziness.

TCA’s may exacerbate medical conditions such as epilepsy, prostatic hyperplasia and pre- existing arrhythmias.