📚 L10 Antidepressants Ii

📚 Lecture Overview

This summary covers the key pharmacological characteristics, adverse reaction profiles, and prescribing guidelines for major antidepressant classes, including SSRIs, TCAs, MAOIs, SNRIs, NaSSAs, and SARIs. It details critical drug interactions, safety risks like Serotonin Syndrome and Tyramine-induced hypertensive crisis, and the clinical management of antidepressant discontinuation. Mastering these concepts is essential for understanding drug safety profiles, managing treatment-emergent side effects, and safely prescribing psychotropic medications.

🎯 Key Concepts & Definitions

• Serotonin Syndrome: A potentially life-threatening condition caused by excessive serotonergic activity, characterized by cognitive, autonomic, and somatic symptoms.
• Hypertensive Cheese Reaction: Malignant hypertension resulting from the interaction between MAOIs and dietary tyramine found in aged or fermented foods.
• Antidepressant Discontinuation Syndrome: A cluster of physical and psychological symptoms occurring after the abrupt cessation of an antidepressant taken for at least 6 weeks.
• Vortioxetine: An SSRI with a long half-life (66 hours) that can be stopped abruptly without causing discontinuation syndrome.
• Medication-Induced Depression: Depression triggered by underlying pharmacological treatments, such as corticosteroids, beta-blockers, or methyldopa.

📖 Main Content

1. Adverse Effects of Antidepressants

Sleep Disturbances & Sexual Dysfunction

• Sleep disturbances: Common adverse reaction across multiple antidepressant classes.
• Sexual Dysfunction: Symptoms include loss of libido and delayed ejaculation.
• Mechanism: There is a reciprocal relationship where serotonin inhibits and dopamine enhances sexual function.
• Management:
  • Bupropion (promotes dopamine) can reverse SSRI-induced sexual dysfunction.
  • SNRIs (inhibit dopamine transporter) cause fewer sexual problems.
  • SARI and NaSSA block $5-HT_2$ receptors, offsetting sexual side effects.

Bleeding Risk & Serotonin Syndrome

• Bleeding: Blocking serotonin reuptake increases bleeding risk in patients taking antiplatelets or anticoagulants.
• NaSSA is considered a safer alternative for patients at high risk of bleeding.
• Serotonin Syndrome:
• Triggers: High doses of SSRIs or concurrent use with serotonergic drugs (e.g., triptans, tramadol).
• Clinical Triad:
  • Cognitive: Delirium, coma
  • Autonomic: Hypertension, tachycardia
  • Somatic: Tremor

2. Tricyclic Antidepressant (TCA) Receptor Blockade

TCAs block three main non-target receptor types, leading to specific adverse effect profiles:

3. MAOI Interactions & Discontinuation Syndrome

Tyramine-Induced Hypertension (Cheese Reaction)

• Mechanism: MAOIs prevent the enzymatic breakdown of tyramine in the gut.
• Pathophysiology: High serum tyramine enhances peripheral noradrenergic effects, causing dramatic blood pressure spikes and malignant hypertension.
• Dietary Precautions: Patients must adhere to a low-tyramine diet and avoid:
• Aged cheeses
• Soy products

Antidepressant Discontinuation Syndrome

• Trigger: Abrupt cessation after taking an antidepressant for $≥ 6$ weeks.
• Risk Factors: Longer duration of treatment and drugs with a shorter half-life.
• Clinical Presentation: Mild flu-like symptoms, insomnia, nausea, imbalance, and sensory disturbances.
• Course & Management: Lasts 1–2 weeks; rapidly resolves upon reinstituting the drug, followed by a slow tapering process.
• Exception: Vortioxetine (long half-life of 66 hours) can be stopped abruptly without tapering.

4. Basic Principles of Prescribing Antidepressants

1. Rule out medication-induced depression: Check for culprit drugs including corticosteroids, beta-blockers, and methyldopa.
2. Titrate dose: Adjust dose progressively according to clinical response.
3. Treatment Duration: For a single depressive episode, continue treatment for at least 6–9 months after symptom resolution.
4. Withdrawal: Always withdraw antidepressants gradually (unless using a long half-life agent like vortioxetine).

📊 Visual Learning

Diagram 1: Serotonin Syndrome Triad and Triggers

Diagram 2: TCA Adverse Effects by Receptor

Diagram 3: Antidepressant Side Effect Management

💡 Important Points to Remember

• Serotonin inhibits sexual function, whereas dopamine enhances it.
• Bupropion can reverse SSRI-induced sexual dysfunction by promoting dopamine.
• NaSSA is the drug of choice for patients at high risk of bleeding who require an antidepressant.
• The Serotonin Syndrome triad consists of cognitive (delirium/coma), autonomic (hypertension/tachycardia), and somatic (tremor) manifestations.
• Mixing SSRIs with tramadol or triptans significantly increases the risk of Serotonin Syndrome.
• Central muscarinic blockade by TCAs causes confusion and amnesia, particularly in elderly patients.
• TCA-induced $\alpha_1$-adrenoceptor blockade leads to orthostatic hypotension and reflex tachycardia.
• High serum tyramine from eating aged cheese while on MAOIs causes malignant hypertension.
• Discontinuation syndrome occurs after stopping antidepressants taken for at least 6 weeks.
• Vortioxetine has a half-life of 66 hours and does not require tapering.
• Always check for corticosteroids, beta-blockers, or methyldopa before diagnosing primary depression.
• Continue antidepressant treatment for 6–9 months after complete symptom resolution in a single depressive episode.

⚠️ Common Exam Questions & Traps

How Examiners Trick Students:

1. Reversal of Sexual Dysfunction: Question scenarios often present a patient responding well to an SSRI but complaining of delayed ejaculation or loss of libido.
   - Exam Trap: Students often select stopping treatment or switching to another SSRI.
   - Correct Answer: Add bupropion or switch to SNRIs, NaSSA, or SARI.
2. Abrupt Antidepressant Cessation: MCQs will list several antidepressants and ask which one can be stopped abruptly without risk of discontinuation syndrome.
   - Exam Trap: Students pick short-acting SSRIs.
   - Correct Answer: Vortioxetine, because of its 66-hour half-life.
3. TCA Receptor Adverse Effects: Questions will match a specific TCA side effect with its receptor mechanism.
   - Exam Trap: Confusing muscarinic central effects (confusion/amnesia) with $H_1$ blockade effects (sedation).
   - Remember: Orthostatic hypotension = $\alpha_1$; Sedation/Weight gain = $H_1$; Dry mouth/Retention/Confusion = Muscarinic.
4. Drug-Induced Depression: A clinical vignette describes a patient presenting with depression who recently started new non-psychiatric medications.
   - Exam Trap: Immediately prescribing an antidepressant.
   - Correct Answer: Identify and manage secondary depression caused by beta-blockers, corticosteroids, or methyldopa.

📝 Quick Review Checklist

I can explain why bupropion reverses SSRI-induced sexual dysfunction.
I can state the triad of Serotonin Syndrome symptoms (cognitive, autonomic, somatic).
I can list the three receptors blocked by TCAs and their associated side effects.
I know which foods patients on MAOIs must avoid to prevent malignant hypertension.
I understand the risk factors, timeline, and management of antidepressant discontinuation syndrome.
I know why vortioxetine can be stopped abruptly.
I can recall the three non-psychiatric drug classes that cause medication-induced depression.
I know the minimum duration of antidepressant therapy following resolution of a single depressive episode.