The danger with cutting medication patches

ISMP error alert

In a case recently reported to the Institute for Safe Medication Practices (ISMP), a physician instructed staff from a hospice health care agency to cut a 50 mcg/h fentanyl transdermal system patch in half and apply it to a patient to deliver a 25 mcg/h dose.

Soon thereafter, a visiting nurse discovered the cut patch, immediately removed it, and called the agency to notify the physician about the risk of an overdose with this practice and to request a supply of 25 mcg/h patches.

This patient suffered no adverse effects; however, serious harm, including death, has been reported under similar circumstances in which patients cut and applied a reservoir membrane fentanyl patch to their skin. These patients intended to reduce the dose delivered, but received an overdose instead.

Varieties of transdermal patches

In the United States, several transdermal drug delivery systems exist, as described in a July 15, 2008, article in the American Journal of Health-System Pharmacy.

Reservoir membrane–modulated systems. In these products, the drug is contained in a reservoir between an impermeable backing layer and a rate-controlling microporous membrane. Drug release is controlled by the membrane. Cutting the patch makes the entire dose available immediately. An example of this type of system is Duragesic (fentanyl—Janssen).

Microreservoir systems. The drug is contained in multiple, smaller drug reservoirs in these patches. Cutting the patch destroys some of the reservoirs, although most remain intact. The number of reservoirs that remain may not be proportionate to the surface area of the patch, however. Therefore, cutting a patch in half does not guarantee that the amount of drug in each half is equal. Catapres-TTS (clonidine—Boehringer Ingelheim) is an example of this system.

Drug in adhesive layer systems. With these patches, the drug is homogeneously mixed with a polymer-based adhesive applied to an impermeable backing. The amount of drug delivered is diffusion controlled and directly proportional to the surface area of the patch. Cutting the patch will decrease the amount of drug delivered without presenting a hazard. Lidoderm (lidocaine—Endo) patches fall into this category and can be safely cut to deliver a smaller dose.

Matrix systems. The drug is evenly distributed throughout an adhesive matrix in these patches, similar to a drug in adhesive layer system. Again, the amount of available drug is directly proportional to the surface area of the patch. Cutting the patch may be possible, but it may also reduce the efficacy of the adhesive. An example of this type of system is Vivelle-Dot (estradiol—Novartis).

Most fentanyl patches are available as reservoir membrane–modulated systems. Product labeling clearly notes that these patches should never be cut or altered. A fentanyl transdermal matrix system patch is available from Mylan; however, labeling for this product specifically warns users not to divide, cut, or damage the patch before application. No formal studies have been done to determine the clinical effectiveness of cut fentanyl matrix patches.

No fentanyl transdermal patches should ever be cut to titrate doses. Instead, health care providers should provide patients with a new prescription for a reduced strength of the patch. Patients should be warned about the risks associated with cutting certain patches.

Anonymous patches

Nurses and pharmacists have reported that Catapres (clonidine) patches can present problems because Boehringer Ingelheim does not print the drug name or strength on the patch. The patches are available in a variety of strengths and are worn for a week at a time.

ISMP has received reports detailing problems when the dose of the drug is changed or the patient requires multiple patches. Long-term care settings may be particularly vulnerable to problems. Because the Catapres patch does not contain the name of the drug, caregivers can determine only that something is on the skin. They cannot determine the drug, the dose, or, in some cases, even distinguish it from adhesive bandages and specialty dressings.

There is a code on each Catapres patch that can be used to identify the strength: “BI 33” designates a 0.3-mg patch, “BI 32” 0.2 mg, and “BI 31” 0.1 mg. Share these codes when dispensing these patches to educate patients about this issue. In addition, tell patients to keep an accurate, up-to-date list of their medications, including the date each patch was applied. Long-term care pharmacies and facilities should consider attaching a notation about these Catapres code designations along with the items in their inventory so that dosing information appears on computer-generated medication administration records.