Pharmacology of Tricyclic Antidepressants

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Questions and Answers

Which of the following antidepressants are less likely to cause muscarinic blockade?

Monoamine Oxidase Inhibitors

Serotonin and Noradrenaline Uptake Inhibitors

Tricyclic Antidepressants

Selective Serotonin Reuptake Inhibitors (correct)

What is a potential consequence of combining SSRIs with MAOIs?

Anxiolytic effect

Cardiac arrhythmia

Anticholinergic syndrome

Serotonin syndrome (correct)

Which SSRI has partial agonist activity at 5-HT1A and 5-HT1B receptors?

Fluoxetine

Paroxetine

Vortioxetine (correct)

Sertraline

What is a common side effect of SSRIs?

Nausea Signup and view all the answers

Which of the following is NOT a condition treated by SSRIs?

Hypertension Signup and view all the answers

What is the typical plasma half-life of most SSRIs?

18-24 hours Signup and view all the answers

Which of the following is a characteristic of venlafaxine?

Relatively non-selective for 5-HT and noradrenaline uptake Signup and view all the answers

What is a potential consequence of combining TCAs with anaesthetic agents?

Potentiation of the effects of anaesthetic agents Signup and view all the answers

What is the primary mechanism of action of Tricyclic Antidepressants (TCAs)?

Non-selectively inhibiting the reuptake of monoamines Signup and view all the answers

What is a common side effect of Tricyclic Antidepressants (TCAs) due to their antimuscarinic effects?

Both dry mouth and urinary retention Signup and view all the answers

Which of the following is NOT a receptor affected by Tricyclic Antidepressants (TCAs)?

Dopamine receptors Signup and view all the answers

What is the approximate time period before the effects of Tricyclic Antidepressants (TCAs) are observed?

2-4 weeks Signup and view all the answers

What is a unique feature of Imipramine?

It is used to control nocturnal enuresis in children Signup and view all the answers

What is the reason for the narrow therapeutic index of Tricyclic Antidepressants (TCAs)?

They have a low therapeutic index due to their narrow therapeutic window Signup and view all the answers

What is the primary route of elimination for Tricyclic Antidepressants (TCAs)?

Hepatic metabolism by microsomal cytochrome P450 enzymes Signup and view all the answers

Which of the following is a potential interaction to be aware of when prescribing Tricyclic Antidepressants (TCAs)?

Inhibited metabolism with competing drugs (e.g., antipsychotic drugs and some steroids) Signup and view all the answers

Study Notes

Tricyclic Anti-Depressants (TCAs)

TCAs are still widely used, but they have limitations, such as delayed onset of action and numerous side effects.
Examples of TCAs include imipramine, desipramine, amitriptyline, nortriptyline, and clomipramine.
TCAs act as non-selective inhibitors of monoamine reuptake, increasing the release of neurotransmitters like 5-HT and NA.
They also block α-2 receptors, which are presynaptic auto-regulatory receptors, leading to the release of monoamines.
TCAs affect other receptors, including muscarinic acetylcholine receptors, histamine receptors, and 5-HT receptors.
Antimuscarinic effects of TCAs are responsible for various side effects.
TCAs improve mood, mental alertness, and physical activity, but take around 2-4 weeks to show their effect.
Imipramine is also used to control nocturnal enuresis in children (off-label use).
TCAs have a narrow therapeutic index and can cause adverse effects when combined with other drugs.

Side Effects of TCAs

Blurred vision
Dry mouth
Urinary retention
Cardiac dysrhythmia and possible ventricular fibrillation
Orthostatic hypotension (α1 blockade)
Sedation

Selective Serotonin Reuptake Inhibitors (SSRIs)

Examples of SSRIs include citalopram, escitalopram, fluoxetine, vortioxetine, fluvoxamine, paroxetine, and sertraline.
SSRIs also block the reuptake of monoamine neurotransmitters, but have 300-fold greater selectivity for serotonin transporters.
They are less likely to cause muscarinic blockade and are less dangerous in overdose.
SSRIs are commonly prescribed for depression, anxiety disorders, and premature ejaculation.
They take around 2-4 weeks to show their effect.
Individual patients may respond more favorably to one SSRI than another.

Side Effects of SSRIs

Nausea
Anorexia
Insomnia
Loss of libido and failure of orgasm
Can prolong the cardiac QT interval and cause sudden death

Serotonin and Noradrenaline Uptake Inhibitors (SNRIs)

Examples of SNRIs include venlafaxine, desvenlafaxine, and duloxetine.
SNRIs are relatively non-selective for 5-HT and noradrenaline uptake.
As the dose of venlafaxine is increased, its efficacy also increases.

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Description

Learn about the mechanism of action, advantages, and disadvantages of Tricyclic Antidepressants (TCAs) such as imipramine and amitriptyline. Discover how they compare to newer antidepressants.