Selective Serotonin Reuptake Inhibitors (SSRIs) Doses

Questions and Answers

What is the primary mechanism of action of SNRIs?

Inhibition of serotonin and norepinephrine reuptake (correct)

Inhibition of dopamine reuptake

Activation of serotonin receptors

Blocking histamine receptors

Which of the following conditions may SNRIs be particularly effective for?

Depression with chronic pain symptoms (correct)

Panic disorder

Bipolar disorder

Obsessive-compulsive disorder

Which of the following statements about Duloxetine is TRUE?

It is associated with a higher incidence of anticholinergic symptoms compared to other SNRIs. (correct)

It has negligible anticholinergic effects in all cases.

It does not require dosage adjustments for renal impairment.

It has the highest incidence of serotonin syndrome among SNRIs.

What distinguishes SNRIs from tricyclic antidepressants (TCAs) regarding receptor effects?

SNRIs have negligible effects at other receptors responsible for anticholinergic symptoms. Signup and view all the answers

Which of the following best describes the side effects associated with SNRIs?

They may induce serotonin syndrome and withdrawal symptoms if abruptly stopped. Signup and view all the answers

Which of the following SNRIs is recognized as the active metabolite of Venlafaxine?

Desvenlafaxine Signup and view all the answers

What is the recommended maximum dose for Venlafaxine in adults?

375 mg/day Signup and view all the answers

What potential risk is associated with SNRIs that is lower compared to TCAs?

Risk of suicide Signup and view all the answers

Which of the following describes Venlafaxine's effect on norepinephrine reuptake?

It inhibits norepinephrine reuptake only at doses of 150 mg/day or higher. Signup and view all the answers

Which of the following adverse effects is most commonly associated with SNRIs?

Nausea Signup and view all the answers

Study Notes

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.