Anti Depressants

Antidepressants are medications used to treat major depressive disorder (MDD) and other mood disorders such as anxiety, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD). They work by altering the levels of neurotransmitters in the brain, such as serotonin, norepinephrine, and dopamine, which are involved in regulating mood and emotions. Below is an overview of the different classes of antidepressant drugs and their mechanisms of action.

1. Selective Serotonin Reuptake Inhibitors (SSRIs)

• Examples: Fluoxetine (Prozac), sertraline (Zoloft), escitalopram (Lexapro), paroxetine (Paxil).

• Mechanism: SSRIs selectively inhibit the reuptake of serotonin, a neurotransmitter that helps regulate mood, anxiety, and happiness. By increasing serotonin levels in the brain, SSRIs help alleviate symptoms of depression and anxiety.

• Use: SSRIs are the most commonly prescribed antidepressants due to their relatively favorable side effect profile. They are effective for major depressive disorder (MDD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), panic disorder, and post-traumatic stress disorder (PTSD).

• Side Effects: Common side effects include nausea, insomnia, sexual dysfunction, weight gain, and drowsiness. They are generally considered safer than older antidepressants like tricyclics.

2. Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs)

• Examples: Venlafaxine (Effexor), duloxetine (Cymbalta), desvenlafaxine (Pristiq).

• Mechanism: SNRIs block the reuptake of both serotonin and norepinephrine, two neurotransmitters involved in regulating mood and stress response. This dual action can provide more significant relief for some patients, especially those with more severe depression.

• Use: SNRIs are often prescribed for major depressive disorder (MDD), generalized anxiety disorder, fibromyalgia, and chronic pain conditions like diabetic neuropathy.

• Side Effects: Side effects can include nausea, dizziness, dry mouth, sexual dysfunction, increased blood pressure, and insomnia. SNRIs may also cause withdrawal symptoms if discontinued suddenly.

3. Tricyclic Antidepressants (TCAs)

• Examples: Amitriptyline, imipramine, nortriptyline, desipramine.

• Mechanism: TCAs work by inhibiting the reuptake of serotonin and norepinephrine. They also block certain receptors (e.g., histamine, acetylcholine), which can cause a range of side effects.

• Use: TCAs are effective in treating major depressive disorder, panic disorder, chronic pain, and neuropathic pain. However, they are not often first-line treatments due to their side effect profile.

• Side Effects: Common side effects include dry mouth, constipation, urinary retention, blurred vision, weight gain, sedation, and cardiac arrhythmias. TCAs are more likely to cause serious side effects, especially in overdose situations.

4. Monoamine Oxidase Inhibitors (MAOIs)

• Examples: Phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan).

• Mechanism: MAOIs inhibit the enzyme monoamine oxidase, which breaks down serotonin, norepinephrine, and dopamine. By preventing the breakdown of these neurotransmitters, MAOIs help to elevate mood and improve depressive symptoms.

• Use: MAOIs are typically reserved for patients who have not responded to other antidepressants, as they have many dietary restrictions and interactions. They are used for major depressive disorder (MDD) and panic disorder.

• Side Effects: MAOIs can cause weight gain, sexual dysfunction, insomnia, and hypertensive crisis when combined with foods containing tyramine (e.g., aged cheese, cured meats, wine). They are less commonly prescribed due to the need for strict dietary adherence and drug interactions.

5. Atypical Antidepressants

• Examples: Bupropion (Wellbutrin), mirtazapine (Remeron), trazodone.

• Mechanism: Atypical antidepressants have unique mechanisms of action. For instance, bupropion inhibits the reuptake of dopamine and norepinephrine, while mirtazapine increases the release of serotonin and norepinephrine by blocking specific receptors.

• Use: These drugs are used for major depressive disorder (MDD), seasonal affective disorder (SAD), insomnia (e.g., trazodone), and smoking cessation (e.g., bupropion).

• Side Effects:

  • Bupropion: Can cause insomnia, dry mouth, seizures (especially in patients with eating disorders), and is often used for patients who experience sexual dysfunction with SSRIs.

  • Mirtazapine: Often used in depressed patients with insomnia or significant weight loss, but it can cause sedation, weight gain, and increased appetite.

  • Trazodone: Frequently used off-label for insomnia due to its sedative properties, but it can cause drowsiness, orthostatic hypotension, and priapism (a rare but serious side effect).

6. Other Considerations

• Onset of Action: Antidepressants typically take 2 to 4 weeks to show noticeable effects, and the full therapeutic benefit may take 6 to 8 weeks.

• Withdrawal Symptoms: Some antidepressants, particularly SSRIs and SNRIs, can cause withdrawal symptoms if stopped suddenly, including dizziness, irritability, flu-like symptoms, and sensory disturbances. Tapering off gradually is recommended.

• Suicidal Thoughts: In the early stages of treatment, especially in younger adults and adolescents, antidepressants may increase the risk of suicidal thoughts or behavior. Patients should be monitored closely during this period.