Antidepressants

Key Points

• Antidepressants require 2+ weeks to begin effect, and noticeable mood improvement commonly takes 4-8 weeks
• For OCD, SSRI regimens commonly require higher daily doses and may need about 8-12 weeks before clear response
• SSRIs are first-line; TCAs and MAOIs are first-generation with more serious adverse effects
• Black Box Warning: Antidepressants increase risk of suicidal ideation in children, adolescents, and young adults (<25 years) — monitor closely in first weeks of therapy
• Serotonin syndrome: Hyperpyrexia, muscle rigidity, altered mental status, hyperreflexia — occurs when serotonergic agents are combined
• MAOIs + tyramine-containing foods → hypertensive crisis (aged cheese, cured meats, alcohol, soy sauce)
• Never discontinue antidepressants abruptly; use prescriber-guided tapering (often 2-6 weeks between dose reductions)
• After remission, treatment is commonly continued for at least about 6 months; longer maintenance may be needed when relapse risk is high

Drug Class Overview

Antidepressants treat major depressive disorder (MDD) and are also used for anxiety disorders, OCD, PTSD, neuropathic pain, insomnia, and smoking cessation. Individual response varies, and patients may need to try multiple classes to find an effective agent. Some early improvement can occur after 2+ weeks, but noticeable mood improvement commonly requires 4-8 weeks. If symptoms persist after at least two antidepressant trials, treatment-resistant pathways (for example intranasal esketamine in a supervised setting with an oral antidepressant) may be considered by prescribers.

Antidepressant Classes

SSRIs (Selective Serotonin Reuptake Inhibitors) — First Line

Mechanism: Block serotonin reuptake at presynaptic nerve terminal → serotonin accumulates in synapse → enhanced postsynaptic receptor activation.

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

Indications: MDD, OCD, PTSD, panic disorder, social anxiety disorder, PMDD, bulimia nervosa.

For pediatric major depression, FDA-approved SSRIs are fluoxetine for children age 8 years and older and escitalopram for adolescents age 12 years and older.

For OCD treatment specifically, therapeutic response often requires higher SSRI dosing than depression regimens and a longer response window (about 8-12 weeks).

For some SSRI regimens (notably fluoxetine in selected clients), clinically meaningful antidepressant response may continue to build over as long as about 12 weeks.

Key Side Effects: Sexual dysfunction (most common reason patients stop medication), nausea, headache, insomnia, nervousness, weight gain. Increased GI bleeding risk — use caution with NSAIDs, aspirin, and anticoagulants.

Additional nursing cautions: Contraindicated with MAOIs; use caution with liver dysfunction and concurrent serotonergic/CNS-active medications. Some references advise avoiding grapefruit juice with selected SSRI regimens due to CYP-mediated interaction potential.

Interindividual metabolism can vary significantly with CYP450 polymorphism patterns, so dose tolerance and adverse-effect burden may differ across clients; use response-based titration and close ADR surveillance.

MAOI Washout:

• Most SSRIs → 2 weeks before/after MAOI
• Fluoxetine (long half-life) → 5 weeks before starting MAOI

SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors)

Mechanism: Block reuptake of both serotonin and norepinephrine.

Examples: Venlafaxine (Effexor), duloxetine (Cymbalta).

Indications: MDD, generalized anxiety disorder, diabetic peripheral neuropathy (duloxetine), fibromyalgia.

Monitoring priorities:

• Venlafaxine can cause sustained blood pressure elevation; monitor BP during titration and maintenance
• In older adults, monitor for hyponatremia
• Use caution in renal/hepatic impairment and adjust dosing when indicated
• Track appetite/weight changes, insomnia/anxiety activation, and increased bleeding risk with NSAIDs/anticoagulants
• In long-term therapy, monitor lipids/cholesterol when clinically indicated
• Late-pregnancy exposure can produce neonatal adaptation/withdrawal patterns (for example irritability, tremor, respiratory distress, and feeding difficulty), so coordinate perinatal risk-benefit review.

NDRIs (Norepinephrine-Dopamine Reuptake Inhibitors)

Example: Bupropion (Wellbutrin).

Indications: MDD, seasonal affective disorder, ADHD, smoking cessation.

Critical note: Bupropion decreases seizure threshold — contraindicated in eating disorders (risk of seizure from electrolyte imbalance) and current seizure disorders.

Neuropsychiatric activation risk (for example agitation, paranoia, hallucinations, hostility, or suicidal ideation changes) requires close early-treatment monitoring, especially when used for smoking-cessation pathways.

SARIs (Serotonin Antagonist and Reuptake Inhibitors)

Example: Trazodone.

Primary Use: Most commonly prescribed off-label as a sedative/hypnotic for insomnia. Reduces arousal neurotransmitters (serotonin, dopamine, noradrenaline, histamine). Administer in the evening.

Miscellaneous Antidepressants

Examples: Mirtazapine, vortioxetine.

Clinical notes:

• Mirtazapine commonly causes sedation, appetite increase, and weight gain; baseline and follow-up metabolic trend monitoring (weight, lipids, glycemic risk context) is important.
• Rare but serious neutropenia/agranulocytosis warning context exists; escalate new fever, sore throat, chills, or flu-like malaise promptly.

TCAs (Tricyclic Antidepressants) — Second Line

Mechanism: Block reuptake of serotonin and norepinephrine; also block muscarinic, histamine, and alpha-1 adrenergic receptors.

Examples: Amitriptyline (Elavil), nortriptyline.

Current Indications: Neuropathic pain, insomnia, migraine prophylaxis (primarily used for these now, not first-line for depression).

Adverse Effects (from receptor blockade):

Receptor Blocked	Adverse Effect
Muscarinic (anticholinergic)	Dry mouth, blurred vision, urinary retention, constipation (constipation), confusion
Histamine	Sedation, weight gain
Alpha-1 adrenergic	orthostatic-hypotension (Orthostatic hypotension)
Cardiac conduction	QTc prolongation, dysrhythmias, cardiotoxicity

Risk in Older Adults: Increased sensitivity to anticholinergic effects → confusion, falls, delirium. Start at lowest dose; monitor closely.

Overdose: Potentially fatal (especially with alcohol). For overdose: call 911 (outpatient) or rapid response (inpatient). Consult Poison Control: 1-800-222-1222.

Contraindications: Recent myocardial infarction, cardiac dysrhythmia, angle-closure glaucoma, children <12 years.

TCA Cardiac Risk

TCAs prolong the QTc interval → risk of life-threatening dysrhythmias (torsades de pointes). Use with extreme caution in patients with electrolyte abnormalities or bradycardia.

MAOIs (Monoamine Oxidase Inhibitors) — Rarely Used / Last Resort

Mechanism: Inhibit monoamine oxidase enzyme → prevents breakdown of serotonin, norepinephrine, and dopamine → elevated levels of all three.

Examples: Phenelzine, tranylcypromine.

Selegiline transdermal pathway is also used in selected major-depression regimens.

Critical Danger: Hypertensive crisis when combined with tyramine-containing foods or stimulant/sympathomimetic drugs. Severe blood pressure elevation (often >180/120 mm Hg) with end-organ injury is a medical emergency.

Tyramine-Restricted Foods (avoid completely while taking MAOIs):

• Aged cheeses (cheddar, blue cheese, brie)
• Cured or smoked meats (salami, pepperoni)
• Alcoholic beverages (especially beer, red wine)
• Soy sauce, miso, teriyaki
• Fermented or pickled foods

Drug Interactions: MAOIs are contraindicated with ALL other antidepressants, stimulants, and sympathomimetic agents. Avoid over-the-counter pseudoephedrine while on MAOIs.

Opioid combinations can precipitate severe hyperpyrexic reactions; diabetic clients may need closer glucose trend review because MAOIs can potentiate hypoglycemia.

Additional risk profile: Orthostatic hypotension, hepatotoxicity, and seizure risk can occur; diabetic clients may develop hypoglycemia. Discontinue and escalate care if hepatotoxicity is suspected.

Critical Safety Warnings

Serotonin Syndrome

Occurs when multiple serotonergic agents are combined (SSRIs + MAOIs, tramadol, triptans, linezolid) or serotonergic doses are rapidly escalated. Typical onset is within 24 hours. SHIVERS cues: Shivering, Hyperreflexia, Increased temperature, Vital-sign instability, Encephalopathy, Restlessness, Sweating. Immediate treatment includes stopping serotonergic agents and hospital-level supportive care (including IV fluids); severe cases may require cyproheptadine. Delayed recognition can progress to rhabdomyolysis and acute kidney injury.

Suicidal Ideation — Black Box Warning

All antidepressants carry FDA Black Box Warning for increased suicidal ideation in patients under 25 years. Monitor most closely during first weeks of therapy and after dose changes. Establish safety contract; assess for access to lethal means.

Nursing Assessment and Interventions

Before Starting:

• Assess baseline mood, suicidal ideation (Columbia Suicide Severity Rating Scale), current medications for interactions
• Teach patient that effect requires 2–6 weeks — do not stop prematurely
• For MAOIs: complete dietary restrictions teaching before first dose
• Obtain baseline weight/BMI and consider baseline ECG (especially adults over 50 years or clients with cardiac-risk context).
• Review baseline labs as ordered (for example CBC, electrolytes, liver profile, glucose/A1c, lipids) and anticoagulation status when relevant (for example warfarin pathways).

Ongoing Monitoring:

• Suicidal ideation — especially first weeks of therapy in patients ≤24 years
• Activation signals such as increased agitation, impulsivity, or new manic-like symptoms after initiation or dose change
• Monitor QTc interval for TCAs (baseline ECG)
• Older adults on TCAs: fall risk, anticholinergic burden, confusion
• Report serotonin syndrome symptoms immediately
• Trend blood pressure and heart rate regularly during titration and maintenance, with closer follow-up when SNRIs are used.
• For mirtazapine pathways, monitor weight and metabolic trends and escalate potential infection cues that may indicate low WBC burden.

Patient Education:

• Do not stop suddenly — taper under provider guidance to prevent discontinuation syndrome (flu-like symptoms, dizziness, irritability); taper plans commonly space dose reductions by 2-6 weeks
• Avoid alcohol (increases CNS depression, increases overdose risk)
• SSRIs: take with food to reduce nausea; avoid concurrent NSAIDs/aspirin without provider guidance
• MAOIs: strict tyramine diet restriction for entire course of therapy plus 2 weeks after discontinuation
• MAOIs: teach hypertensive-crisis warning symptoms (severe headache, palpitations, neck stiffness, chest tightness, confusion, severe hypertension) and emergency escalation
• Use sun protection when photosensitivity-prone regimens are prescribed and report severe rash or unusual skin reactions.

Related Concepts

• psychopharmacology — Broader psychiatric medication overview including antipsychotics and mood stabilizers
• depression — Pathophysiology and nursing care for depressive disorders
• substance-use-disorders — Alcohol interactions and contraindications with antidepressants
• self-harm-and-suicide — Risk assessment for patients starting antidepressant therapy
• anxiolytics — Concurrent anxiety treatment often paired with antidepressants
• analgesics — TCAs used as adjuvant analgesics for neuropathic pain

Self-Check

1. A patient on fluoxetine is prescribed a MAOI for refractory depression. What is the minimum washout period, and why?
2. What are the classic signs of serotonin syndrome, and which drug combination commonly causes it?
3. A patient taking amitriptyline reports dry mouth, difficulty urinating, and constipation. What receptor blockade explains these symptoms?