Cutting Patches for Dosage Adjustment
Medication patches are available in a limited number of dosage strengths. Occasionally, some patients require a different dosage of a medication than the dosages commercially available in patch form. Alteration of a TDDS (i.e., cutting the patch to reduce the surface area) may be an option to provide alternative doses. However, many patches should not be cut or altered in any way. Some medications are only effective at specific and exact doses; such is the case with patches used for contraception. Additionally, alteration of the patch may interfere with the way it was designed to deliver medication. Even when alteration of a patch is deemed safe and appropriate, clinicians must consider changes that may occur in the adhesive qualities of the patch, as cutting can result in sharp corners or an odd shape. Information regarding the alteration of patches is not frequently addressed in the medical literature or in the prescribing information.
Patches of the reservoir type should not be cut, as cutting destroys the rate-controlling ability of the membrane and can lead to delivery of the entire drug dose immediately on application. Depending on the medication type, the cutting of a patch that uses a microreservoir system can be safe and appropriate, but some of the reservoirs will be destroyed when the patch is cut; consequently, it cannot be guaranteed, for example, that if a patch is cut in half, 50% of the dose will be delivered to the patient. In contrast, drug-in-adhesive matrix systems deliver an amount of medication proportional to the area covered by the TDDS and can thus theoretically be safely cut; a currently available lidocaine patch is one example of such a product.
Generally, most TDDS manufacturers recommend against the use of a patch that has been altered; in most cases, bioavailability studies to determine the effects of cutting a particular patch on safety and efficacy have not been conducted. Despite the use of similar patch designs, different manufacturers of clonidine patches included in this review provided different recommendations on the cutting of patches. Data from a few small studies demonstrate the efficacy of clonidine patches applied after cutting.[11,12] Results were favorable and showed that the amount of drug delivered was proportional to the surface area. To help ensure the safe and appropriate use of medication patches, clinicians should be familiar with different TDDS types and whether a product may be cut, considering the safety, efficacy, and patch design. Furthermore, to help prevent adverse drug reactions, health care professionals should provide appropriate counseling to patients regarding safety and efficacy issues associated with cutting patches. The appendix includes specific information regarding manufacturer recommendations on cutting commonly used FDA-approved patches.
Am J Health Syst Pharm. 2012;69(2):116-124. © 2012 American Society of Health-System Pharmacists, Inc.
All rights reserved. Posted with permission.