Summary Safety Review - INTUNIV XR (guanfacine hydrochloride) - Assessing the Potential Risk of Raynaud's Phenomenon

August 15, 2016

Product

Intuniv XR (guanfacine hydrochloride extended-release tablets)

Potential Safety Issue

Raynaud's phenomenon

Key Messages

• Intuniv XR is used to treat Attention Deficit Hyperactivity Disorder (ADHD) in children and adolescents 6 to 17 years.
• Health Canada reviewed the use of Intuniv XR and the risk of Raynaud's phenomenon, a disorder of the blood circulation in fingers and toes that causes the skin to turn pale or blue.
• Health Canada's safety review did not find sufficient evidence to support strengthening the product safety information that already exists for this side effect. Health Canada will continue to monitor the safety of this medicine.

Overview

A safety review was carried out to evaluate the potential risk of Raynaud's phenomenon in patients taking Intuniv XR. Raynaud's phenomenon is a disorder of the blood vessels, mainly in the fingers and toes, where they episodically do not receive enough blood and oxygen. The resulting lack of blood and oxygen causes numbness and the skin will turn a pale or bluish colour. Most episodes of this phenomenon last about 15 minutes but in severe cases this can cause damage to the skin and muscle (through oxygen deprivation and tissue death). Health Canada started a review because other drugs used to treat ADHD contain warnings in their product safety information about the risk of Raynaud's phenomenon. The review aimed to determine whether there was enough evidence to include a similar stronger warning for Intuniv XR.

Use in Canada

• Intuniv XR is used for the treatment of ADHD in children and adolescents aged 6 to 17 years.
• Intuniv XR is a once-a-day, extended-release tablet that is available in 1 mg, 2 mg, 3 mg and 4 mg doses.
• Although not commonly prescribed, Intuniv XR use has been increasing since it entered the Canadian market in August 2013.

Safety Review Findings

• At the time of the review, Health Canada had received 1 Canadian report^{Footnote a} of Raynaud's phenomenon with the use of Intuniv XR. Although the case report lacked detailed information, the review found that it was possible that Intuniv XR caused the Raynaud's phenomenon.
• Health Canada's review of the 30 reports received from the manufacturer was limited in its ability to confirm and assess the potential role of Intuniv XR. In general, the reports lacked details, including information to determine if the patient was actually experiencing Raynaud's phenomenon.
• There was no direct evidence in the literature to support the risk of Raynaud's phenomenon with the use of Intuniv XR and other guanfacine-containing products used in other countries.
• The product safety information of Intuniv XR lists Raynaud's phenomenon as a "less frequent" and "possibly guanfacine-related" event.

Conclusions and Actions

• Health Canada's safety review findings did not support strengthening the existing product safety information for Intuniv XR on the risk of Reynaud's phenomenon.
• Health Canada will continue to monitor side effect information involving Intuniv XR, as it does for all health products on the Canadian market, to identify and assess potential harms. Health Canada will take appropriate and timely action if and when new health risks are identified.

Additional Information

The analysis that contributed to this safety review included scientific and medical literature, Canadian and international adverse reaction reports and what is known about the use of this drug both in Canada and internationally.

For additional information, contact the Marketed Health Products Directorate.