11. Antidepressants, behaviour modifiers

Question 1

What are antidepressants?

Answer 1

They are are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction

Question 2

Name the most important drug groups

Answer 2

• TCA, Tricylcic antidepressants
• SSRI, Selective Serotonin Reuptake Inhibitors
• Tetracyclic antidepressant

Question 3

TCA, Tricylcic antidepressants,
active substances

Answer 3

Clomipramine

Question 4

Selective Serotonin Reuptake Inhibitors, Active substances

Answer 4

Fluxoetine

Question 5

Tetracyclic antidepressants, Active substances

Answer 5

Mirtazepine

Question 6

Selective Serotonin Reuptake Inhibitors, Mechanism of action

Answer 6

The SSRI works by increasing the amount of serotonin available in the brain. Serotonin is a neurotransmitter that helps regulate the mood, sleep, appetite and behaviour.
Nerve cells in the brain release serotonin to communicate with each other. After serotonin is reabsorbed back into the nerve cell that released it (called reuptake).

SSRIs block this reuptake process, and cause more serotonin to remain in the space between nerve cells (the synapse).

This increased amount of serotonin allows it to bind more receptors on the receiving nerve cell, enhancing serotonin’s effect.

In short: SSRI helps to make more of serotonin available, which can improve the mood and reduce anxiety or compulsive behaviours.

Question 7

Selective Serotonin Reuptake Inhibitors, indication

Answer 7

• Aggression
• Depression
• Separation anxiety
• Feline urine spraying

Question 8

Selective Serotonin Reuptake Inhibitors, pharmacokinetics

Answer 8

1. Absorption: Good oral absorption, up to 70% gets into the bloodstream
2. Metabolism: Liver metabolises the drug by using CYP enzymes
   It takes 7-9 days before the body is rid of half of the drug

Question 9

Selective Serotonin Reuptake Inhibitors, side effects

Answer 9

• Vomiting
• Diarrhoea
• Diabetes mellitus
• Epilepsy
• Liver and renal failure

Question 10

Tricyclic antidepressants,
Mechanism of action

Answer 10

The drug blocks SERT and NET receptors, which usually take up serotonin, norepinephrine and dopamine. By blocking these receptors, the drug stops the nerve cells from reabsorbing the neurotransmitters.

The blocking will cause accumulation of serotonin, norepinephrine and dopamine in the brain, which can improve mood and behaviour.

The tricyclic antidepressants also block adrenergic receptors (alpha-1), anticholinergic (mAchR) and histamine receptors

Question 11

Tricyclic antidepressants,
pharmacokinetics

Answer 11

1. Absorption: Good oral absorption
2. Distribution: High protein binding
3. Metabolism: Liver
4. Excretion/elimination: urine
   !! It takes 2-3 weeks for the drug to reach a steady concentration with regular dosing!!

Question 12

Tricyclic antidepressants,
side effects

Answer 12

• Moderate sedation
• Cardiac
• Appetite changes
• Dry mouth
• Urinary retention