In this discussion, we will delve into the major classes of antidepressants, starting with the most widely prescribed: the serotonin-specific reuptake inhibitors (SSRIs). These drugs have well-defined neurotransmitter profiles and are crucial in treating major depressive disorder (MDD).
Diagnosing Depression: The SIG E CAPS Mnemonic
To diagnose MDD, remember the mnemonic SIG E CAPS:
- Sleep disturbances
- Interest loss (anhedonia)
- Guilt or feelings of worthlessness
- Energy loss
- Concentration difficulties
- Appetite changes
- Psychomotor agitation or retardation
- Suicidal thoughts
A patient must exhibit at least five of these symptoms for at least two weeks to qualify for an MDD diagnosis.
Serotonin-Specific Reuptake Inhibitors (SSRIs)
Mechanism of Action
SSRIs work by inhibiting the serotonin transporter on presynaptic neurons, increasing the amount of active serotonin in the synaptic cleft.
Common SSRIs
- Fluoxetine (Prozac)
- Long half-life: beneficial for patients who forget to take medications regularly.
- Risk of serotonin syndrome if switched too quickly to another serotonergic drug.
- Mnemonic: “Flu” and its association with a one-week duration helps remember the long-lasting effect.
- Sertraline (Zoloft)
- Notable for causing gastrointestinal side effects (nausea, diarrhea).
- Safer for pregnant or breastfeeding women due to lower levels in breast milk.
- Mnemonic: “Squirt-raleen” for the GI side effects.
- Paroxetine (Paxil)
- Rapid absorption leading to more pronounced initial side effects.
- Rapid withdrawal can lead to uncomfortable symptoms.
- Mnemonic: “Pair of oxen” for rapid onset and withdrawal.
- Citalopram (Celexa)
- High tolerability, considered a good first-line agent.
- Can prolong the QTc interval, necessitating EKG monitoring at higher doses.
- Mnemonic: “Celexa” and “car” to remember the need for an electrocardiogram.
- Escitalopram (Lexapro)
- The S-enantiomer of citalopram, with fewer enzyme interactions.
- Mnemonic: “Lexapro” as the “awesome younger sibling” of Celexa.
- Fluvoxamine (Luvox)
- Approved for treating obsessive-compulsive disorder (OCD) in the U.S.
- Mnemonic: “Luvox” with “OC” for obsessive-compulsive.
Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)
- Venlafaxine (Effexor)
- Inhibits the reuptake of both serotonin and norepinephrine.
- Useful for symptoms of low energy, decreased interest, and impaired concentration.
- Risk of hypertension due to norepinephrine effects.
- Mnemonic: “Venlafaxine” and the “N” sound for norepinephrine.
- Duloxetine (Cymbalta)
- Dual action on serotonin and norepinephrine.
- Also used for chronic pain conditions.
- Mnemonic: “Dul” for dual mechanism, and “dulls” the pain.
Other Antidepressants
- Mirtazapine (Remeron)
- Enhances sympathetic output by inhibiting inhibitory inputs.
- Increases appetite and decreases nausea, useful in cancer and HIV patients.
- Mnemonic: “Meal-tazapine” for its effect on appetite.
- Bupropion (Wellbutrin)
- Works on dopamine and norepinephrine.
- No significant serotonergic effects, less sexual dysfunction.
- Helps with smoking cessation.
- Mnemonic: “Butane” for the dopamine and norepinephrine effects.
- Trazodone (Desyrel)
- Used as an antidepressant and a sleep aid.
- Can cause priapism (prolonged erection).
- Mnemonic: “Trouser-bone” for the priapism side effect.
Tricyclic Antidepressants (TCAs)
- Complex binding profiles affecting serotonin, norepinephrine, acetylcholine, histamine, sodium, and calcium ion channels.
- Effective but with significant side effects and toxicity in overdose.
- Mnemonic: “Trans, Chan’s, and Anne’s” for the multiple neurotransmitter effects and ion channels.
Common TCAs
- Imipramine
- Used for nocturnal enuresis (bedwetting) in children.
- Mnemonic: “I’m peeing-Ramin.”
- Clomipramine
- Approved for OCD treatment.
- Mnemonic: “Clomipramine” for OCD.
- Amitriptyline and Nortriptyline
- Also used for chronic pain conditions.
Monoamine Oxidase Inhibitors (MAOIs)
- Effective for atypical depression but with severe side effects.
- Can cause hypertensive crisis when combined with tyramine-rich foods.
- Mnemonic: “Maui with Tyra Banks” for MAOIs and tyramine.
Common MAOIs
- Selegiline (Eldepryl)
- Selective for MAO-B.
- Mnemonic: “Select-a-lien” for selectivity.
- Phenelzine (Nardil)
- Non-selective, affecting both MAO-A and MAO-B.
- Preferable for depression treatment.
Review and Referral Criteria (PSYCH MD)
- P: Psychosis
- S: Suicidality
- Y: “Why isn’t this working?” (treatment-resistant)
- C: Comorbid psychiatric disorders
- H: Highs and lows of bipolar disorder
- MD: Monitoring drugs like lithium