Considerations before cutting or masking patches 

Modification of transdermal patches, such as cutting or masking, is not routinely recommended. It should only be considered when no suitable licensed alternatives are available to meet the clinical needs of the patient.

We do not endorse or recommend altering transdermal patches. This article outlines key considerations to support clinical decision making where modification of patches is being considered as a last resort.

Modifying a patch, either by cutting or masking, changes its formulation characteristics and will be outside of the product licence. The General Medical Council provides guidance on the responsibilities associated with prescribing unlicensed medicines.

Key issues to consider:

• most manufacturers cannot guarantee uniform drug distribution across the patch – this may result in inaccurate dosing or dose dumping
• there is often a lack of data on the efficacy or stability of cut or masked patches

Before deciding to cut or mask a patch, consider whether: 

• the patch is available in different strengths for dose flexibility
• a higher dose could be achieved by using multiple patches
• switching to a different drug such as from fentanyl to buprenorphine may be more suitable
• a non-patch formulation might be more suitable

If, after these considerations, a decision is made to proceed, assess the safety risks specific to the patch being modified.

For example, the MHRA Drug Safety Update advises against cutting fentanyl patches due to the risk of life-threatening or fatal opioid toxicity.

Where no suitable licensed alternatives are available and a clinical need remains, consider the pharmaceutical implications before modifying the patch. Assess whether cutting or masking part of the patch may be the safer or more appropriate approach.

Cutting transdermal patches

There are three types of transdermal patch: matrix, reservoir, and micro-reservoir. Understanding the specific type is essential, as only certain patches are suitable for cutting.

Sections 3 and 6.1 of the Summary of Product Characteristics usually detail the characteristics of the patch. Alternatively, contact the manufacturer. 

Matrix patches

Matrix patches may be cut if no licensed alternative exists. However, doing so may still alter the release characteristics of the drug, leading to unpredictable dosing and effects.

Medication within a matrix patch is either dispersed within the adhesive or in a separate matrix layer between the backing and adhesive layers. 

Reservoir patches

Do not cut reservoir patches. Cutting can cause the inner gel to leak and lead to serious safety risks. These patches contain medicine in a gel-filled reservoir with a rate-limiting membrane to control release. 

Cutting reservoir patches can result in:

• rapid drug release, known as dose dumping, increasing the risk of toxicity
• rapid drop in drug concentration following initial drug release, causing minimal or no drug delivered
• accidental transfer of medication to others, such as the person handling the patch

Exception

Hyoscine hydrobromide (Scopoderm) reservoir patches are sometimes cut in paediatrics. There is no other viable treatment option for children and the risk of dosing errors is lower compared with opioid patches.  The BNF for Children provides advice on how to do this.

Even so, the MHRA warns of serious and life-threatening anticholinergic side effects from hyoscine hydrobromide patches, especially when used outside the product licence. 

Micro-reservoir patches

Micro-reservoir patches should only be cut if there are no other alternatives. These patches contain multiple small reservoirs of medication rather than a single large one. 

Cutting micro-reservoir patches may alter drug delivery, though the risk is lower than with standard reservoir patches.

Cutting patches safely and accurately

The decision to cut a patch should only apply to a specific brand and strength and must not be generalised for other products.

Patients or carers must be fully counselled on the potential risks and instructed on how to handle and use the modified patch safely.

Tips for cutting patches

For most patches the amount of drug released is proportional to the surface area in contact with the skin. Accurate and safe cutting is therefore essential to ensure appropriate dosing.

Consider the following:

• for accuracy, cut square or rectangular patches diagonally from corner to corner to create halves or quarters
• gently mark cutting lines with a ruler and pen or pencil before cutting, taking care not to damage the patch surface
• use sharp scissors; blunt scissors can create ragged edges reducing the patch’s ability to adhere to the skin
• do not cut patches in advance as patch stability can vary

Using cut patches

Sharp edges from the cut patch may reduce adhesion to the skin. Use surgical adhesive tape such as Micropore® to secure the edges to skin and aid adherence. See our article Managing problems when using transdermal patches for advice on adhesion issues. 

Dispose of any unused portion according to local policy. 

Masking part of the patch

Masking part of a transdermal patch with an impermeable dressing may sometimes be considered in clinical practice to deliver a reduced dose. However, this is outside of the product licence with limited supporting data and introduces additional risks.

Risks of masking patches

Masking patches is more complex and carries additional risks compared with standard application or cutting:

• the unused portion remains in place, increasing risk of incorrect reapplication if adhesive fails
• accurate positioning of the patch over the dressing can be challenging
• confusion between dressings and patches can lead to missed doses or double application
• patch adhesives are designed for skin contact, and their effectiveness on dressings is uncertain
• more drug remains in the patch, raising risk of transverse movement of the drug or accidental exposure, especially if dressing is removed

If masking is chosen after all options are considered, including the pharmaceutical properties of the patch, the decision must be clearly documented.

Recommendations should only apply to a specific brand and strength, and should not be generalised across products.

Patients or carers must be counselled on potential risks and instructed how to handle and use the modified patch safely.

Tips for masking patches

If cutting is not an option and masking is considered clinically appropriate, follow these steps:

• use an impermeable (occlusive) dressing
• cut dressing to required size
• if needed, mark patch to indicate where the dressing should be applied
• use additional tape or a secondary dressing to secure patch if required – for more information, see our article Managing problems when using transdermal patches