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Transdermal patches during MRI procedures: risk of serious burns

Recently, the Food and Drug Administration (FDA) issued a Public Health Advisory expressing concern about patients wearing transdermal patches while undergoing magnetic resonance imaging (MRI) procedures.¹ This concern stems from reports of patients experiencing skin burns in the area surrounding and beneath the patch during imaging and from information regarding this risk missing from the product labeling of certain transdermal patches.^1-3 The following article provides an overview of the mechanism of injury, some recommendations to minimize the risk, and information on the components of some transdermal patches.

Transdermal patches and mechanism of injury
This risk of burn injury is not present with all transdermal patches. Transdermal patches associated with burns during MRI procedures contain an aluminum foil or metal layer that helps to contain the drug as well as inactive ingredients in the patch.¹ Transdermal patches vary in composition and may contain a combination of layers containing active drug and inactive ingredients, an adhesive, a membrane to control release of drug, a backing to protect the contents of the patch from the environment, and a liner to protect the contents while stored. Because of the variability in the components and appearance of the patch, it may not be possible to visibly distinguish patches formulated with a metal component from those without metal.⁴

Magnetic resonance imaging is based on alignment of atomic nuclei following exposure to a magnetic field.⁵ Currents result from both the magnetic field generated as well as a generated pulsed radiofrequency field. During an MRI, an image is formed from the detection of the pulsed radiofrequency field traveling through the patient. The metal layer present in some transdermal patches may act as a conductor of current generated by the pulsed radiofrequency field and result in intense heat. This heat is trapped between the transdermal patch and the skin, potentially resulting in second-degree burns.²

Several patient cases have been published, describing blistering, burning, and erythematous skin during MRI procedures where a transdermal patch was in placed.^2,3 One reported incident resulted in the termination of the exam within less than 40 seconds in response to a patient complaining of his arm burning. This was later was found to be caused by a nicotine replacement transdermal patch. During a similar case, a patient’s restless movements resulted in early cessation of the procedure; the patient explained that his arm was burning in the area where a transdermal patch was affixed to his skin.

Prevention of transdermal patch-associated MRI injury
The American College of Radiology (ACR) Blue Ribbon Panel on MR Safety, has published a guidance document on safe practices during an MRI.^6-8 Included in this document is general information on the management of patients wearing transdermal patches. Prior to examination, these guidelines state that all patients should be screened by trained MR staff, with 1 or 2 screenings recommended, depending on the urgency of the MRI. For a non-emergent MRI, at least 1 of 2 screenings must be performed by staff extensively trained in MR safety (e.g., MR technicians, radiologists, or radiology department nurses, rather than MRI department staff or patient aides). In an emergency case, only 1 patient screening is expected; however, these patients must be screened by the more qualified staff members. If a patient will undergo sedation for the MRI procedure, a complete medical history, examination and screening should be performed prior to sedating the patient. By following such screening procedures as recommended by the ACR, the likelihood of missing key patient information, such as the use of a transdermal patch, is minimized. Specific to patients using transdermal patches, these guidelines identify the risk of thermal injury if a patient is scanned in the area of the patch. Before a patient using a transdermal patch undergoes an MRI, a consultation with the prescribing physician or the primary care physician should be undertaken to develop a management strategy for the patch, including removal of the patch prior to imaging and re-applying when the imaging is complete. To make sure the transdermal patch is re-applied prior to the patient leaving the department after the MRI is complete, the panel suggests one staff member be in charge of replacing the patch at the completion of the MRI. Alternatively, an ice pack may be placed on the area of skin where the patch is applied, in situations where removal of the patch is not possible.

The FDA is in the process of reviewing prescription and over-the-counter patches to assess each product’s risk of causing burns during an MRI procedure and to ensure that this information is clearly stated in the product labeling.¹ If indicated, the FDA will require labeling changes to address the risks during MRI procedures for any transdermal patch containing metal components. Until the FDA completes the process of identifying the specific patches that pose a risk of burns during an MRI, they have cited specific recommendations to avoid any adverse event. The FDA suggests for following for patients:

• Inform the referring physician about any medicated transdermal patches as well as the indication for use.
• Before the MRI, ask your physician for specific instructions about removing and disposing of the patch and replacing the patch following the procedure.
• Tell the MRI facility about the patch:
• When you make the appointment.
• During the health history assessment.
• The day you arrive for the MRI.

In addition to the recommendations posed by the FDA, additional safety measures should be followed. Educating MRI staff on proper patient assessment will help to avoid patients from “slipping through the cracks.”^9,10 During patient screening, patients should be specifically asked if they are wearing any drug patches and should be given specific examples of such transdermal patches. Inpatient and outpatient MRI facilities should consider posting a warning about the hazards of wearing patches during an MRI procedure. If there is any concern regarding the removal of the patch for the duration of the procedure, the patient’s physician should be contacted for a recommendation about how to properly manage the patient.^5,9-11 Healthcare practitioners who encounter a patient who experiences an MRI-induced burn associated with the use of a transdermal patch, should report the event to the FDA via the MedWatch program. Reports can be made via the internet at http://www.fda.gov/medwatch/index.html or via phone at (800)-FDA-1088.¹

Summary
Education about mechanisms causing injury during an MRI procedure, adherence to published guidelines, and attention to recommendations from the FDA will lessen the risk of transdermal patch-associated injury during MRI procedures. Multiple preventative mechanisms before MRI procedures should be put in place to avoid any patient from experiencing burns related to transdermal patches. The table below describes the characteristics of various transdermal patches, to help determine the safety of use during MRI procedures. However, whenever the components of a transdermal patch are unknown, it is better to err on the safe side and consult the prescribing physician regarding removal of the patch.

References