9. Mechanism of Action
• The exact mechanism is unknown. The predominant action is by
increasing catecholamine levels in the brain.
• TCAs are also called as Mono Amine Reuptake Inhibitors (MARls).
The main mode of action is by blocking the reuptake of norepinephrine
(NE) and/ or serotonin (5-HT)at the nerve terminals, thus increasing
the NE and 5-HTlevels at the receptor site.
10. Mechanism of Action
• MAOIs instead act on MAO (monoamineoxidase),which is responsible
for the degradation of catecholamines after re-uptake. The final effect
is the same, a functional increase in the NE and 5-HT levels at the
receptor site. The increase in brain amine levels is probably responsible
for the antidepressant action. It takes about 5 to 10days for MAOIs and
2 to 3 weeks for TCAs to bring down depressive symptoms.
• SSRIs act by inhibiting the re-uptake of serotonin and increasing its
levels at the receptor site.
17. 6. Special effects of MAOI drugs:
Hypertensive crises,
Severe hepatic necrosis,
Hyperpyrexia.
18. Nurse's Responsibility for a Patient
Receiving Antidepressants
• Most of the nurse's responsibilities for a patient on antidepressants are
the same as for a patient receiving antipsychotics . In addition:
• Patients on MAOIs should be warned against the danger of ingesting
tyramine-rich foods which can result in hypertensive crisis.
• Some of these foods are beef liver, chicken liver, fermented sausages,
dried fish, over riped fruits, chocolate and beverages like wine, beer
and coffee.
19. Cont..,
• Report promptly if occipital headache, nausea, vomiting, chest pain or
other unusual symptoms occur ; these can herald the onset of
hypertensive crisis.
• Instruct the patient not to take any medication without prescription.
• Caution the patient to change his position slowly to minimize
orthostatic hypotension.
• Strict monitoring of vitals, especially blood pressure is essential.