Medically reviewed by Jessica Swirble, PharmD
Last updated on March 16, 2024

Drug Information | Side Effects | Use & Dosage | Request a Prescription

The use of guanfacine has been shown to cause side effects in some patients.

Common mild side effects of guanfacine use include:

• Drowsiness
  
• Fatigue or weakness
  
• Irritability
  
• Headache
  
• Dizziness
  
• Dry mouth
  
• Constipation
  
• Stomach pain
  
• Decreased appetite
  
• Decreased libido
  
• Insomnia
  
  

More severe side effects include:

• Hypotension (low blood pressure)
  
• Bradycardia (slow heart rate)
  
• Fainting
  
• Mood changes or depression
  
• Severe allergic reactions (rash, itching, swelling)
  
  

Seek medical attention immediately if you experience any severe symptoms while taking guanfacine. If you experience mild side effects that become severe or do not go away after a few days, speak to a healthcare provider right away.

Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with guanfacine. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with this drug.

Tell your provider if you are taking these medications or supplements:

• Other ADHD medications
  
• Antihistamines
  
• Blood pressure medications
  
• Heart medications
  
• Sedatives or tranquilizers
  
• Antidepressants
  
• Anti-anxiety medication
  
• Certain seizure medications
  
• HIV medication
  
  

You should also mention medical conditions such as:

• Heart problems
  
• Liver or kidney disease
  
• Low blood pressure
  
• Recent stroke or heart attack
  
• Recent or upcoming surgery (including dental surgery)
  
  

If you are pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider before using guanfacine to assess potential risks and benefits.

You can follow your regular diet while taking guanfacine. Avoiding activities requiring mental alertness, such as driving or operating heavy machinery, is essential until you know how guanfacine affects you. Guanfacine can cause drowsiness, dizziness, and lightheadedness.

Avoid consuming alcohol while taking guanfacine, as it may increase the risk of side effects such as drowsiness and dizziness.

Avoid eating grapefruit or drinking grapefruit while taking guanfacine. Grapefruit can increase the effects of guanfacine, leading to more side effects.

Extended-release guanfacine should not be taken with a high-fat meal.

Your healthcare provider will provide specific instructions regarding the use of guanfacine with food, beverages, and other medications. It's essential to follow their guidance to ensure the effectiveness of the treatment and minimize the risk of side effects.

If you suspect an overdose of guanfacine or experience severe symptoms, seek immediate medical attention or contact a poison control center. Symptoms of an overdose may include drowsiness, dizziness, fainting, slow heart rate, and difficulty breathing.

If an individual has collapsed, is having seizures, or is unresponsive, call 9-1-1 immediately.