The common suffixes for tricyclic antidepressants (TCAs) are (2) .
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 28-year old female presents to the ER with cardiac abnormalities following an attempted suicide with tricyclic antidepressants. She is lucid and has not experienced seizures. What is the next step in management?
This disorder causes a persistent feeling of sadness and loss of interest in everyday activities.
Alright, now within the brain, there are many different types of neurons, but we’re just going to focus on two: serotonergic neurons which produce serotonin, and noradrenergic neurons which produces norepinephrine.
Each of these neurons synthesizes and stores their neurotransmitters in small vesicles.
So, when an action potential reaches the presynaptic membrane, these vesicles fuse with the membrane, releasing neurotransmitters into the synaptic cleft.
Once released, serotonin or 5-HT binds to 5-HT2 receptors on the postsynaptic membrane, thereby increasing neural stimulation and regulating mood, feeding, and reproductive behavior.
As long as there’s a high enough concentration of neurotransmitters in the synaptic cleft, the postsynaptic neurons will continue to fire.
These membrane proteins transport the serotonin and norepinephrine in the synaptic cleft back into presynaptic neurons.
This leads to decreased neurotransmitter concentration within the synaptic cleft, causing the postsynaptic neurons to stop firing.
Tertiary TCAs are also known as non-selective tricyclic antidepressants and they inhibit both serotonin transporters and norepinephrine transporters, while secondary TCAs, which are also known as selective tricyclic antidepressants, inhibit only norepinephrine transporters.
It's important to note that these medications are slow-acting because it takes time for serotonin and norepinephrine to accumulate within the synaptic cleft. Because of this, it usually takes 2-4 weeks before improvements can be seen.
Now, for medication specific indications, clomipramine can be used in the treatment of obsessive-compulsive disorder, or OCD, while imipramine is used in the treatment of nocturnal enuresis, which is involuntary urination while asleep.
Besides serotonin and norepinephrine transporters, TCAs also block histamine H1 receptors, causing sedation; alpha 1 receptors, causing orthostatic hypotension; and muscarinic receptors, causing atropine-like side effects.
- "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
- "Rang and Dale's Pharmacology" Elsevier (2019)
- "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
- "Mechanism of action of antidepressant medications" J Clin Psychiatry (1990)
- "Tricyclic antidepressant pharmacology and therapeutic drug interactions updated" British Journal of Pharmacology (2007)
- "Tricyclic antidepressant overdose: a review" Emerg Med J (2001)
- "Neuroleptic malignant syndrome and serotonin syndrome" Thermoregulation: From Basic Neuroscience to Clinical Neurology, Part II (2018)