Medical Warning: Common Sleep Drug May Impair Driving and Focus the Next Day

A new medical study is raising concerns about a commonly prescribed medication sometimes used to help people sleep, warning that it may leave dangerous effects the next morning — even when patients feel awake.

The drug is quetiapine, known by the brand name Seroquel. It is approved to treat conditions such as schizophrenia and bipolar disorder, but it is increasingly prescribed at much lower doses for insomnia, anxiety and general sleep complaints because of its sedating effect, according to Flinders University.

Researchers at Flinders University in Australia found that a low dose of quetiapine may make sleep appear better on the surface, but may also reduce next-day safety by slowing reaction time, increasing lapses in attention and weakening steering control during a driving simulation.

The study focused on adults with obstructive sleep apnea and difficulty maintaining sleep. Compared with a placebo, quetiapine improved sleep efficiency and reduced breathing interruptions during sleep, without worsening oxygen levels. However, the same trial found poorer performance the following morning in tests linked to real-world crash risk.

One of the most concerning findings was that some participants did not feel especially sleepy the next day, even though their objective test results showed weaker performance. Researchers said this mismatch between how people feel and how they actually function can create a serious safety risk, especially when driving or doing work that requires full alertness.

The findings also point to a wider medical issue: sleep problems may sometimes be a sign of an underlying disorder, such as obstructive sleep apnea, rather than a simple case of insomnia. Flinders University researchers noted that many people with sleep apnea remain undiagnosed, and that sedating medication may mask the problem instead of treating the cause.

The warning is not limited to quetiapine. The U.S. Food and Drug Administration has previously reminded the public that all drugs taken for insomnia can impair driving and other activities that require alertness the morning after use, even if the person feels fully awake. The FDA also said that over-the-counter insomnia medicines may carry a risk of next-morning impairment.

Mayo Clinic also warns that many nonprescription sleep aids contain antihistamines, including diphenhydramine and doxylamine, which can leave users feeling groggy and unwell the next day. Mayo Clinic advises people not to drive or attempt activities requiring alertness while taking sleep aids, and notes that these products are not intended for long-term use.

Doctors say the main message is that sleeping longer does not always mean waking up safer. A person may get more hours of sleep but still have slower reactions, weaker focus or reduced judgment the next morning.

Patients should not stop quetiapine or change their dose on their own, especially if it was prescribed for a psychiatric or neurological condition. But anyone using it mainly for sleep, or experiencing morning drowsiness, dizziness, confusion, falls, slow reaction time or difficulty driving, should speak with a doctor or pharmacist.

For long-term insomnia, Mayo Clinic says behavioural changes learned through cognitive behavioural therapy are generally the best treatment, while prescription sleeping pills should be used carefully and with medical guidance