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Questions and Answers
Which of the following antidepressants are less likely to cause muscarinic blockade?
What is a potential consequence of combining SSRIs with MAOIs?
Which SSRI has partial agonist activity at 5-HT1A and 5-HT1B receptors?
What is a common side effect of SSRIs?
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Which of the following is NOT a condition treated by SSRIs?
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What is the typical plasma half-life of most SSRIs?
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Which of the following is a characteristic of venlafaxine?
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What is a potential consequence of combining TCAs with anaesthetic agents?
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What is the primary mechanism of action of Tricyclic Antidepressants (TCAs)?
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What is a common side effect of Tricyclic Antidepressants (TCAs) due to their antimuscarinic effects?
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Which of the following is NOT a receptor affected by Tricyclic Antidepressants (TCAs)?
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What is the approximate time period before the effects of Tricyclic Antidepressants (TCAs) are observed?
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What is a unique feature of Imipramine?
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What is the reason for the narrow therapeutic index of Tricyclic Antidepressants (TCAs)?
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What is the primary route of elimination for Tricyclic Antidepressants (TCAs)?
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Which of the following is a potential interaction to be aware of when prescribing Tricyclic Antidepressants (TCAs)?
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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.
