From the Guidelines
Dextromethorphan is considered a non-sedating opiate, but it can still cause drowsiness as a side effect in some individuals, particularly at higher doses or in sensitive populations. This common cough suppressant, found in many over-the-counter cold medications, works by affecting signals in the brain that trigger the cough reflex. According to a study published in Thorax 1, dextromethorphan has been shown to suppress acute cough in a single meta-analysis, with a dose response and maximum cough reflex suppression occurring at 60 mg. However, another study published in Chest 1 discusses the use of various antitussive pharmacologic agents, including dextromethorphan, in the setting of lung cancer, but does not specifically address the issue of drowsiness. Key points to consider when taking dextromethorphan include:
- The drowsiness is typically mild to moderate at recommended doses (usually 15-30 mg taken every 4-8 hours, not exceeding 120 mg in 24 hours for adults)
- This sedative effect may be more pronounced in some individuals, particularly the elderly, those taking other medications that cause drowsiness, or at higher doses
- If you're taking dextromethorphan, avoid driving or operating machinery until you know how it affects you
- The drowsiness side effect is why many cough medicines containing dextromethorphan are labeled with warnings about potential impairment and why some are formulated for nighttime use specifically.
From the Research
Dextromethorphan and Drowsiness
- Dextromethorphan is a commonly used antitussive, and its effects on the central nervous system have been studied for various neurological and psychiatric disorders 2.
- While the provided studies discuss the efficacy and safety of dextromethorphan for treating depression and other conditions, they do not directly address its potential to cause drowsiness.
- However, it is known that dextromethorphan can have effects on the central nervous system, which may include sedative properties 3, 4.
- A study on benzodiazepines, which are known for their sedative effects, mentions that drugs with depressant effects on the central nervous system can cause drowsiness and other related symptoms 5.
- Although dextromethorphan is not a benzodiazepine, its potential to cause drowsiness as a side effect cannot be ruled out without further evidence.
- A study on commonly prescribed medications and potential false-positive urine drug screens mentions dextromethorphan as a medication that can cause false-positive results, but it does not discuss its potential to cause drowsiness 6.