Trazodone
Trazodone is a serotonin antagonist and reuptake inhibitor (SARI) with a unique pharmacological profile that combines antidepressant activity with potent sedative effects. While FDA-approved only for major depressive disorder, it is one of the most commonly prescribed medications for insomnia — a widespread off-label use driven by its sedating properties and lack of the dependence potential seen with benzodiazepines and Z-drugs.
Trazodone is an antidepressant most commonly used off-label for insomnia due to its strong sedating properties. It blocks serotonin reuptake and 5-HT2A receptors. Its sedation at low doses makes it a non-scheduled sleep aid, though it can cause orthostatic hypotension and priapism.
Uses & FDA Indications
Trazodone's FDA-approved indication is major depressive disorder (MDD) in adults. However, prescribing patterns are heavily weighted toward off-label uses, particularly insomnia.
- Major depressive disorder (FDA-approved) — treatment of depressive episodes, often used when sedation is a desired feature (e.g., patients with insomnia as part of their depression)
- Insomnia (off-label) — one of the most commonly used sleep aids in clinical practice; preferred over benzodiazepines in many patients because it is not a controlled substance and does not cause dependence
- Anxiety disorders (off-label) — generalized anxiety disorder, PTSD-related sleep disturbances
- Alzheimer's-related agitation (off-label) — evidence supports use for behavioral symptoms in dementia
- Fibromyalgia (off-label) — may help with sleep and pain modulation
How It Works
Trazodone's mechanism is multifaceted and differs from both SSRIs and tricyclic antidepressants, which explains both its therapeutic versatility and its distinctive side effect profile.
Primary mechanisms:
- 5-HT2A receptor antagonism — blocks postsynaptic serotonin-2A receptors. This enhances slow-wave sleep (the deep, restorative stages), contributes to anxiolytic effects, and is thought to reduce some of the side effects associated with serotonin excess.
- Serotonin reuptake inhibition — weakly blocks the serotonin transporter (SERT), increasing synaptic serotonin availability, contributing to antidepressant effects.
- Alpha-1 adrenergic receptor antagonism — responsible for the prominent sedative effects, orthostatic hypotension, and the rare complication of priapism.
- H1 histamine receptor antagonism — contributes further to sedation.
Unlike SSRIs, trazodone's 5-HT2A antagonism actually improves sleep architecture — increasing time spent in slow-wave sleep and suppressing REM sleep less than many other antidepressants. This makes it uniquely suited for patients who need both antidepressant therapy and improved sleep quality.
Side Effects
Common
- Drowsiness and sedation (the most prominent effect; often the therapeutic target for sleep use)
- Dizziness and lightheadedness
- Headache
- Dry mouth
- Nausea and constipation
- Orthostatic hypotension — blood pressure drops when standing, causing dizziness or fainting
- Blurred vision
- Weight changes
Serious
- Priapism — prolonged, painful erection unrelated to sexual stimulation; occurs in approximately 1 in 6,000 male patients. A medical emergency requiring immediate treatment; can cause permanent erectile dysfunction if untreated.
- Serotonin syndrome — potentially life-threatening; caused by excess serotonergic activity, especially when combined with other serotonergic drugs (SSRIs, MAOIs, tramadol, triptans)
- Suicidal ideation — FDA black box warning: increased risk of suicidal thoughts in children, adolescents, and young adults (under 25) during initial antidepressant treatment
- QT prolongation — potential cardiac arrhythmia risk, especially at higher doses or in combination with other QT-prolonging drugs
- Cardiac arrhythmias — including premature ventricular contractions; monitor in patients with cardiac history
- Hyponatremia — low sodium levels (SIADH); especially in elderly patients
Drug Interactions
| Drug / Class | Interaction | Clinical Significance |
|---|---|---|
| MAOIs (phenelzine, tranylcypromine, selegiline) | Risk of serotonin syndrome — potentially fatal; requires washout period between MAOI and trazodone | High — contraindicated; allow 14-day washout after MAOI |
| SSRIs / SNRIs / other serotonergic drugs | Additive serotonergic activity increases serotonin syndrome risk; monitor for agitation, tremor, hyperthermia, tachycardia | Moderate to high — use with caution; monitor closely |
| CYP3A4 inhibitors (ketoconazole, ritonavir, clarithromycin) | Significantly increase trazodone blood levels, raising risk of adverse effects including QT prolongation and hypotension | High — reduce trazodone dose when combining |
| Digoxin / Phenytoin | Trazodone may increase plasma levels of both drugs, increasing toxicity risk | Moderate — monitor drug levels |
| CNS depressants (opioids, benzodiazepines, alcohol) | Additive CNS and respiratory depression; enhanced sedation | Moderate to high — avoid or minimize combination |
| Antihypertensive drugs | Trazodone's alpha-1 blocking effect can enhance blood pressure-lowering medications, causing hypotension and syncope | Moderate — monitor blood pressure |
Warnings & Contraindications
⚠ BLACK BOX WARNING: Antidepressants, including trazodone, increase the risk of suicidal thinking and behavior in children, adolescents, and young adults (under 25) with major depressive disorder and other psychiatric disorders. Monitor closely for worsening depression, suicidality, or unusual behavioral changes, especially during the first few months of treatment and after dose changes.
- Priapism alert (males): Any erection lasting longer than 2–4 hours should be treated as a medical emergency. Contact a provider or go to the emergency room immediately. Permanent erectile dysfunction can result from delayed treatment.
- MAOI contraindication: Do not use trazodone within 14 days of stopping an MAOI. Do not start an MAOI within 14 days of stopping trazodone.
- Cardiac patients: Use with caution in patients with pre-existing cardiac conditions, particularly arrhythmias or known QT prolongation. Baseline ECG may be warranted.
- Falls risk: Orthostatic hypotension combined with sedation significantly increases fall risk, particularly in elderly patients. Advise patients to rise slowly from sitting or lying positions.
- Driving and machinery: Trazodone causes significant sedation. Patients should not drive or operate heavy machinery until they know how the medication affects them.
FAQ
Why is trazodone prescribed for sleep if it is an antidepressant?
Trazodone's sedative properties — stemming from its histamine and alpha-1 receptor blockade — occur at lower doses than those needed for antidepressant effect. Providers often prescribe it at sub-antidepressant levels specifically for insomnia. It is particularly attractive for sleep because it is not a controlled substance (no DEA scheduling), does not cause the dependence issues associated with benzodiazepines or zolpidem, and actually improves deep sleep architecture rather than simply sedating the patient.
How long does trazodone take to work for depression?
Like most antidepressants, trazodone's full therapeutic effect on depression requires 2–4 weeks of consistent use. The sedative effects are typically noticed from the first dose. Patients should not discontinue trazodone prematurely if they do not see immediate antidepressant benefit — the brain requires sustained changes in receptor sensitivity and neurotransmitter signaling to achieve full benefit.
What is priapism and why does trazodone cause it?
Priapism is a prolonged, painful penile erection that occurs without sexual stimulation and does not resolve with orgasm. Trazodone causes it through its alpha-1 adrenergic receptor blockade, which affects the smooth muscle that controls blood flow in erectile tissue. The frequency is approximately 1 in 6,000 patients. All male patients starting trazodone should be counseled to seek immediate medical attention for any erection lasting more than 2–4 hours.
Can I stop taking trazodone suddenly?
Unlike benzodiazepines or opioids, trazodone does not typically cause severe physical withdrawal. However, abrupt discontinuation can cause discontinuation syndrome symptoms — irritability, anxiety, insomnia, dizziness, and "brain zaps" (electric shock-like sensations). Gradual tapering is recommended when stopping trazodone after regular use, particularly if it has been used for an extended period.
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