M06.15.006 Other Antidepressants & Smoking Cessation

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Learning Objectives

By the end of this session, the learner will be able to distinguish between Atypical Antidepressants based on their unique mechanisms and side-effect profiles and identify the pharmacological role of Varenicline in smoking cessation.

1. Atypical Antidepressants

These agents are frequently used when patients fail SSRIs or require a specific side-effect profile (e.g., needing to avoid sexual dysfunction or needing help with sleep).

Drug Mechanism Clinical “Niche”
Trazodone Blocks 5-HT reuptake and blocks 5-HT₂ receptors. Mainly used off-label for Insomnia; highly sedative.
Bupropion Inhibits DA and NE reuptake (NDRI). Used for depression and Smoking Cessation.
Mirtazapine \alpha_2-antagonist (increases NE/5-HT release) and 5-HT₂ block. Used for depression with insomnia or underweight status.

 

2. High-Yield Toxicity & Contraindications

The “atypical” nature of these drugs leads to very specific, exam-relevant adverse effects.

Side Effect Associated Drug Clinical Importance
Priapism Trazodone A painful, persistent erection; a medical emergency.
Seizures Bupropion Lowers seizure threshold; Contraindicated in Bulimia/Anorexia.
Weight Gain Mirtazapine Potent appetite stimulant; useful in cachectic or elderly patients.

3. Pharmacology of Smoking Cessation

Two primary non-nicotine medications are used to help patients quit smoking by targeting the brain’s reward pathways.

Drug Mechanism Clinical Benefit
Varenicline Partial agonist at nicotinic ACh receptors. Reduces withdrawal symptoms and blocks the reward of smoking.
Bupropion Increases Dopamine and NE in the reward center. Reduces cravings and the urge to smoke.

Clinical Pearls:

  • Sexual Dysfunction: If a patient is distressed by SSRI-induced sexual issues, switching to Bupropion is the classic answer because it does not affect Serotonin.
  • Mirtazapine \alpha_2 Block: By blocking the “brakes” (presynaptic \alpha_2 receptors), it forces the neuron to release more neurotransmitter.
  • Varenicline Safety: Always monitor for neuropsychiatric side effects, including vivid dreams or mood changes.

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