Drowsiness, or feeling abnormally sleepy, is a common side effect of many medications. Drowsiness can affect your ability to drive, operate machinery, or do other things that require alertness. It affects some people more than others. The following types of medications can cause drowsiness:

  • Narcotics used to relieve pain (e.g., codeine, morphine)
  • Certain antianxiety medications (e.g., diazepam, lorazepam, alprazolam)
  • Certain antidepressants (e.g., amitriptyline, fluvoxamine)
  • Certain antihistamines, often found in cold and allergy products (e.g., diphenhydramine, chlorpheniramine). The newer antihistamines (e.g., loratidine, fexofenadine) are much less likely to cause drowsiness, but may still make some people drowsy.

Medications other than those listed above may also cause drowsiness. If you are not sure, check with your pharmacist.

If you are starting a new medication that may cause drowsiness, it is important to avoid activities that require alertness, such as driving, until you find out how the medication affects you. Alcohol can add to the effects of the medication to make you even drowsier. People who did not get drowsy when taking the medication alone may find that they become drowsy when taking the combination of the medication and alcohol.