Selective Serotonin Reuptake Inhibitors (SSRIs) Doses

SSRIs Overview

• Selective Serotonin Reuptake Inhibitors (SSRIs) increase serotonin levels in the synaptic cleft by blocking its reuptake.
• They take at least 2 weeks for noticeable mood improvements, with maximum benefits taking up to 12 weeks.
• Common SSRIs include Fluoxetine, Sertraline, Paroxetine, Fluvoxamine, Citalopram, and Escitalopram, each with specific half-lives and dosing.

SSRI Dosage and Half-Life

• Fluoxetine: Half-life of 1-4 days; Usual dose 20-60 mg/day; Max 80 mg.
• Sertraline: Half-life of 26 hours; Usual dose 50-200 mg/day; Max 200 mg.
• Paroxetine: Half-life of 21 hours; Usual dose 10-60 mg/day; Max 50-60 mg.
• Fluvoxamine: Half-life of 15 hours; Usual dose 50-300 mg/day; Max 300 mg.
• Citalopram: Half-life of 32 hours; Usual dose 20-40 mg/day; Max 40 mg.
• Escitalopram: Half-life of 27-32 hours; Usual dose 10-20 mg/day; Max 20 mg.

Therapeutic Uses of SSRIs

• Effective for depression (excluding fluvoxamine), Generalized Anxiety Disorder (GAD), and Obsessive-Compulsive Disorder (OCD).
• Fluoxetine uniquely treats Bulimia Nervosa and is indicated for stroke recovery and premature ejaculation.

Side Effects of SSRIs

• Generally fewer side effects compared to tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs).
• Common side effects: GI disturbances, headaches, fatigue, sexual dysfunction, weight changes, and sleep disturbances.

Duloxetine (Cymbalta®)

• Inhibits serotonin and norepinephrine reuptake across all doses.
• Indicated for Major Depressive Disorder, GAD, diabetic peripheral neuropathy, fibromyalgia, and chronic musculoskeletal pain.
• Dosage range: 40-120 mg/day.
• Potential side effects: Increased blood pressure, tachycardia, dry mouth, constipation, and liver toxicity in patients with hepatic issues.

Levomilnacipran (Fetzima®)

• A newer SNRI, primarily metabolized by CYP3A4.
• Indicated for Major Depressive Disorder in adults; not for fibromyalgia.
• Dosage: 40-120 mg/day.
• Side effects resemble those of SSRIs, including increased blood pressure and tachycardia.

Norepinephrine Reuptake Inhibitors (NRIs)

• Used for ADHD, narcolepsy, and obesity, along with depression.
• Reboxetine specifically targets Major Depressive Disorder with a standard dose of 10 mg/day (max 20 mg/day).
• Common side effects: Nausea, vomiting, and constipation.

Serotonin/Norepinephrine Reuptake Inhibitors (SNRIs)

• SNRIs inhibit serotonin and norepinephrine reuptake receptors.
• Less likely to cause anticholinergic side effects compared to TCAs, although Duloxetine may present some risk.
• Effective for depression, especially when coupled with chronic pain syndromes.
• Both Duloxetine and Venlafaxine associated with increased suicide risk compared to SSRIs, but lower than that seen with TCAs.

Venlafaxine (Effexor®) and Desvenlafaxine (Pristiq®)

• Venlafaxine: At lower doses, primarily affects serotonin; at medium to high doses, inhibits norepinephrine reuptake.
• Dosage for Venlafaxine: 74-375 mg/day; for Desvenlafaxine (active metabolite), 50-200 mg/day.
• Both have similar side effect profiles, including potential for increased blood pressure and must be monitored accordingly.