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Side Effects of Guanfacine ER

Drowsiness, headaches, and dizziness are some of the common side effects of guanfacine ER. Adverse reactions to this drug are generally mild, and most people taking it have no problems at all. However, serious side effects are possible, such as slow heart rate, unexplained swelling, and extreme drowsiness. These potentially dangerous problems require immediate medical attention.

An Introduction to Guanfacine ER Side Effects

As with any medicine, side effects are possible with guanfacine ER (Intuniv™). However, not everyone who takes the medication will have problems. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or are treated easily by you or your healthcare provider.
(This article covers many, but not all, of the possible guanfacine ER side effects. Your healthcare provider can discuss a more complete list with you.)

Side Effects of Guanfacine ER to Report

There are a number of possible side effects with guanfacine ER that you should report to your healthcare provider. These include but are not limited to:
  • Signs of low blood pressure, such as dizziness, lightheadedness, or fainting
  • A slow heart rate
  • Extreme drowsiness
  • Signs of an allergic reaction, including unexplained rash, hives, itching, unexplained swelling, wheezing, or difficulty breathing or swallowing.

Common Side Effects

Guanfacine ER has been studied thoroughly in clinical trials. In these studies, the side effects that occurred in a group of people taking the drug were documented and compared to those that occurred in another group of people taking a placebo (a "sugar pill" with no active ingredients).
This way, it is possible to see what side effects occurred, how often they appeared, and how they compared to the placebo. However, some studies (especially the long-term studies) did not use a placebo.
In these studies, the most common guanfacine ER side effects included:
  • Drowsiness -- in up to 45 percent of people
  • Headache -- up to 26 percent
  • Fatigue -- up to 15 percent
  • Upper abdominal pain (stomach pain) -- up to 11 percent
  • Low blood pressure (hypotension) -- up to 10 percent
  • Vomiting -- up to 9 percent
  • Dizziness -- up to 7 percent
  • Nausea -- up to 7 percent
  • Weight gain -- up to 7 percent.
Other common adverse reactions, occurring in 3 to 6 percent of people, included:
  • Irritability
  • Decreased appetite
  • Dry mouth
  • Constipation.
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Guanfacine ER Drug Information

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