The biggest side effect of trazodone is drowsiness. In clinical trials, it affected 24% to 41% of patients, making it by far the most frequently reported complaint. This intense sedation is so dominant that it has actually reshaped how the drug is used: trazodone was approved as an antidepressant, but today it’s far more commonly prescribed at lower doses as a sleep aid, essentially turning its most problematic side effect into its primary purpose.
Why Drowsiness Is So Pronounced
Trazodone’s sedating effect comes from the way it interacts with multiple receptor systems in the brain at once. At low doses (25 to 100 mg), it primarily blocks histamine receptors and certain serotonin receptors, both of which contribute to sleepiness. This is why even small doses can make you feel heavily sedated. At higher doses used for depression (150 to 600 mg), the drug starts to have a stronger effect on serotonin reuptake, which is what provides its antidepressant action, but the sedation also intensifies along with it.
The sedation is typically strongest during the first few weeks of treatment. Trazodone has a half-life of roughly 5 to 13 hours, meaning it can take well over 24 hours for a single dose to fully clear your system. For people taking it as a sleep aid, this long clearance time can translate into morning grogginess, sluggish thinking, and a “hangover” feeling that lingers into the next day. This next-day sedation is one of the main reasons people stop taking it.
Other Common Side Effects
Beyond drowsiness, the FDA lists dizziness, constipation, and blurred vision as the most common reactions occurring in at least 5% of patients at twice the rate of placebo. These tend to be dose-dependent, meaning they’re more noticeable at higher doses.
Orthostatic hypotension, a drop in blood pressure when you stand up, affects roughly 4% to 7% of users. Trazodone causes this by blocking a type of receptor in blood vessels that helps regulate blood pressure. For most younger adults, this means occasional lightheadedness when getting up too quickly. For older adults, the consequences can be far more serious. In one study of geriatric outpatients with high blood pressure, those taking trazodone experienced fainting episodes and falls at a rate of 58.3%, compared to 21.2% in those not taking the drug. That’s a striking difference and a major safety consideration for anyone over 65.
Priapism: Rare but Serious
Trazodone carries a rare but potentially dangerous risk of priapism, a prolonged, painful erection lasting four hours or more that occurs without sexual stimulation. The estimated incidence in male patients falls between 1 in 1,000 and 1 in 10,000, with most cases developing within the first month of starting the medication. While statistically uncommon, priapism is a medical emergency. If left untreated, it can cause permanent tissue damage. This risk applies to clitoral tissue as well, though it’s reported far less frequently.
If you experience an erection that won’t resolve on its own within a few hours, this requires immediate emergency treatment, not a next-day phone call to your doctor.
Serotonin Syndrome Risk
Trazodone raises serotonin levels in the brain, which means combining it with other serotonin-boosting substances can push those levels dangerously high. This condition, called serotonin syndrome, can cause agitation, rapid heart rate, high body temperature, muscle twitching, and in severe cases, seizures.
The risk increases when trazodone is taken alongside certain cough medications containing dextromethorphan, other types of antidepressants, supplements like tryptophan or 5-HTP, and the anti-anxiety medication buspirone. Even some melatonin products have been found to be contaminated with 5-HTP, which could raise serotonin levels when combined with trazodone. If you take trazodone alongside any other medication or supplement that affects serotonin, your prescriber needs to know about it.
The FDA’s Boxed Warning
Like all antidepressants, trazodone carries the FDA’s most serious safety label: a boxed warning about increased risk of suicidal thoughts and behaviors in people under 25. This warning is based on pooled data from roughly 77,000 adult patients and over 4,500 pediatric patients across placebo-controlled trials of various antidepressants. The elevated risk was specific to patients aged 24 and younger. Trazodone is not approved for use in children or adolescents.
How Dose Shapes the Side Effect Profile
Your experience with trazodone side effects depends heavily on how much you’re taking. At the low doses typically prescribed for insomnia (25 to 100 mg), sedation is the dominant effect, and most people tolerate it reasonably well since sleepiness is essentially the goal. Orthostatic hypotension, dizziness, and other side effects exist but are generally mild at these doses.
At the higher doses needed for treating depression (150 to 600 mg), both sedation and blood pressure drops become significantly more pronounced, which limits how well many patients tolerate the medication. This is a major reason trazodone has largely been replaced by other antidepressants for depression treatment while remaining widely prescribed as a low-dose sleep aid.
What Happens When You Stop Taking It
Stopping trazodone abruptly can trigger a discontinuation syndrome. Common symptoms include rebound insomnia, mood swings, dizziness, nausea, headaches, flu-like chills and sweating, and in some cases, a disorienting feeling of detachment from yourself or your surroundings. These symptoms are not dangerous, but they can be deeply uncomfortable.
The standard recommendation is to taper the dose gradually over four to six weeks rather than stopping cold turkey. Some people need a longer taper depending on how long they’ve been on the medication and how high their dose is. If withdrawal symptoms become severe during a taper, the typical approach is to step back up to a slightly higher dose and then resume tapering more slowly.