Yes, Dextromethorphan, which is a common ingredient in many over-the-counter cough medicines, can sometimes cause insomnia or difficulty sleeping in some individuals. Dextromethorphan is a cough suppressant, and while it is generally used to relieve coughs due to colds or flu, it can have side effects.
Insomnia is not the most common side effect of Dextromethorphan, but it is reported by some users. This might be due to the stimulating effects it can have on the central nervous system, especially in higher doses.
Other side effects that have been reported with the use of Dextromethorphan include:
Drowsiness
Dizziness
Nausea
Vomiting
Nervousness or restlessness
It's also worth noting that many cough and cold medicines that contain Dextromethorphan also contain other active ingredients, such as decongestants, which can also contribute to insomnia.
As with any medication, it's important to use Dextromethorphan as directed and to be aware of its potential side effects. If you are experiencing difficulty sleeping or other side effects that you believe may be related to Dextromethorphan or any other medication, it's a good idea to consult a healthcare professional.