Medications - What Causes Fatigue: Chronic Fatigue

Content provided by the Faculty of the Harvard Medical School

Medications

Hundreds of over-the-counter and pre­scription drugs can cause daytime drowsiness or fatigue. The most common classes of drugs associated with such side effects are antihistamines, high blood pressure medications, antibiotics, antidepressants, and anti-anxiety drugs.

Drugs can cause sleepiness or fatigue in several ways. Some drugs, such as antihistamines for allergies and colds, do so by depressing the central nervous system. Others initially act as stimulants, but ultimately leave you tired because they keep you awake at night. Among these drugs are theophylline, used to treat asthma and other upper respiratory problems, and nicotine patches to help smokers quit. Still other medications can cause muscle weakness, including certain anti-arrhythmic agents (drugs that normalize an irregular heartbeat).

If you're taking a drug that causes drowsiness or fatigue, don't stop taking it without talking with your doctor. First, not all drugs that can cause such side effects do so in every person who takes them. Just because you're using a medication that can cause fatigue doesn't necessarily mean that it's causing your fatigue. Second, if the drug is the cause of your sleepi­ness or fatigue, your doctor may be able to prescribe another medication that won't have the same effect.

If there's no available substitute, you might be able to reduce the side effects by taking the medication at a time of day when drowsiness or fatigue is less of a problem, such as in the evening. For example, people with allergies can often take an oral antihistamine at night, when its sleep-inducing effect isn't a problem, and control symptoms during the day with a nasal corticosteroid spray, such as budesonide (Rhinocort, Pulmicort), which doesn't cause drowsiness.

Last updated:	January 23, 2007