4. 1. Tricyclic and tetracyclic
antidepressants
● Mechanism of action
● Block the reuptake of serotonin and norepinephrine
at presynaptic nerve ending
● Also block muscarinic, histaminic and alpha
adrenergic receptors
● Metabolized by liver and excreted through kidneys
● Drug levels are increased by drugs that inhibit the
cytochrome p450
6. 1. Tricyclic and tetracyclic
antidepressants
Adverse Effects
● Peripheral:
● Anticholinergic effects: constipation, urinary
hesitancy, dry mouth and blurred vision
● Antihistaminic effects: sedation, weight gain
● Alpha adrenergic effects: orthostatic hypotension
and reflex tachycardia
● Cardiac effects:most worrisome : prolong QT
interval, flatten T waves, ST segment depression
may also increase premature ventricular contractions
7. 1. TCA Continue
● Allergic and hematologic: Rashes,agranulocytosis,
leukopaenia and eosinophilia
● Central Effects:
● Tremors and lowering of seizure threshold
9. 2. Monoamine oxidase inhibitors
● Mechanism of action
● Monoamine oxidase is an enzyme which degrades
serotonin, dopamine, tyramine and norepinephrine
● Block this enzyme
● Two types of mono amine oxidase A and B
● MAO-A brain, liver , gut and sympathetic nerves
● MAO-B brain , liver and platelets
10. 2. MAO inhibitors continued
● Indications
● Depression with anxiety symptoms
● Panic disorders
● Agoraphobia
● Social phobia PTSD
● Bulimia nervosa
● Atypical depression
11. 2. MAO inhibitors continued
● Adverse effects
● Anticholinergic
● Antihistaminic
● Alpha adrenergic blockage
● Most worrisome is the ingestion of tyramine
containing food concomitantly which may
precipitate severe hypertensive crises
● Patients encouraged to avoid such foods
● Patients advised to seek immediate medical attention
when symptoms of crisis appear I.e headache,
12. 2. MAO Inhibitors continue
● Can be treated with nefidipine 10mg tablet or
intravenous phentolamine
● The following foods should be avoided:
● Cheese, fish, meat, caviar, salami, sausages,
overripe or canned fruits,yeast extracts or fermented
products, chocolate, colas, tea, coffee, soya sauce,
beer, wine
● Drugs: OTC pain medication,cold and allergy med,
cough preparations, decongestants, inhalers,
stimulants, diet pills and SSRI
14. 3. Selective serotonin reuptake
inhibitors
● Mechanism of action
● Selectively inhibit the the reuptake of 5HT at
presynaptic neuron
● They lack the side effects of TCA caused by
blockage of muscarinic, alpha adrenergic and
histaminic
● Therefore they are the most widely prescribed
and better tolerated
15. 3. SSRI Continued
● Indications
● Major depressive disorder
● Obsessive compulsive disorder
● Social anxiety disorder
● Panic disorder
● Generalized anxiety disorder
● Post traumatic stress disorder
17. 3. SSRI Continued
● Adverse Effects
● Largely dose related
● Central
● Restlessness, anxiety, muscle tension, insomnia and
headache
● Sedation, vivid dreams
18. 3. SSRI continued
● Peripherally
● GIT: loose bowel movements
● GUT: decrease libido, delay ejaculation and
anorgasmia
● Rare cases of serotonin syndrome reported when
patients take two or more drugs boosting serotonin
levels
● Presents with restlessness, lethargy, mental
confusion, flushing, sweating, tremors and
myoclonic jerks. Later develop hyperthermia,
hypertonicity, rhabdomyolysis, renal failure and
19. 3. SSRI continued
● Inhibit cytochrome p450 isoenzyme therefore can
lead to increase in drugs metabolized by this system
● Safe to use in pregnancy but should be avoided in
breastfeeding
● May not be used concurrently with MAO inhibitors
21. 4. SNRI Continued
● Indications:
● Major depressive disorder
● Generalized anxiety disorder
● Social anxiety
● Panic disorders
● ADHD
● Dual diagnosis of cocaine dependence
22. 4. SNRI continued
● Mechanism of action
● Potent inhibitors of serotonin and norepinephrine
reuptake
● No activity on other receptors
Adverse Effects
● Similar to SSRI
24. 5. DNRI Continued
● Mechanism of action
● Inhibits the reuptake of dopamine and
norepinephrine
● Indications
● Major depressive disorder
● Smoke cessation
● ADHD
25. 5. DNRI Continued
● Well tolerated
● Has minimal effects on weight gain, cardiac
conduction or sexual dysfunction
● Adverse Effects
● Central
● Headaches, anxiety, tremors, insomnia, sweating,
seizures at higher doses.
