Transdermal Patches and Medications

What Are Transdermal Medications?

Transdermal medication is delivered through the skin for systemic effect, via a patch that releases the drug slowly and at a controlled rate into the bloodstream.

How the Patch Works

Layers:

• Backing layer protects the patch from the outside.
• Drug reservoir or matrix holds the medication.
• Release liner protects the drug in storage and peels off before use.
• Adhesive layer sticks it to the skin.

The drug releases at a controlled rate, crosses the skin layers (stratum corneum, epidermis, dermis), and enters the capillaries for systemic distribution.

Advantages

• Controlled release over time.
• Noninvasive, no injection pain or infection risk.
• Bypasses the digestive tract, avoiding stomach acid.
• Bypasses first-pass liver metabolism, delivering more directly to the bloodstream.

Disadvantages

• Local skin reactions, irritation or allergy at the site.
• Variable absorption by individual and by site.
• More expensive than oral medications.
• Limited drug types. Only small, lipophilic molecules deliver well transdermally.

Types of Patches

1. Single-layer drug-in-adhesive. The adhesive layer is both glue and drug reservoir. Simple and easy to make.
2. Multi-layer drug-in-adhesive. Multiple adhesive layers, each with drug, for more controlled release; layers can carry different concentrations.
3. Reservoir. A separate drug reservoir between a backing layer and a rate-controlling membrane, for precise, prolonged delivery.
4. Matrix. The drug sits in a matrix layer between backing and adhesive, diffusing out for a steady release.
5. Vapor patches. Release essential oils or substances that vaporize and are inhaled rather than absorbed; common in aromatherapy.
6. Micro-reservoir. Combines reservoir and matrix: tiny drug reservoirs in a gel-like matrix for controlled, sustained release.

Drugs Given by Patch

• Pain relievers: fentanyl (Duragesic), buprenorphine (Butrans)
• Hormones: estrogen (Estraderm, Vivelle-Dot), testosterone (Androderm)
• Cardiovascular: nitroglycerin (Nitro-Dur, Transderm-Nitro), clonidine (Catapres-TTS)
• Neurological: rivastigmine (Exelon), rotigotine (Neupro)
• Smoking cessation: nicotine (Nicoderm CQ, Nicotrol)
• Antidepressants: selegiline (Emsam)

Side Effects

• Local skin reactions: redness, itching, rash, or swelling at the site.
• Systemic effects depending on the drug: dizziness, nausea, headache, or drug-specific effects.
• Allergic reactions, rare but needing immediate attention.

How to Apply

1. Check the order or label for placement (upper chest, upper outer arm, lower abdomen, or hip) for even absorption.
2. Remove any old patch of the same drug, fold it sticky-sides together, and discard it. This keeps dosing consistent and prevents overdose and irritation.
3. Clean the area with clear water and pat it dry. No soap, alcohol, lotion, or oil, which interfere with adhesion.
4. Open the pouch and remove the patch without touching the adhesive side.
5. Press the adhesive side onto the skin with your palm right away for strong adhesion.
6. Hold firmly for at least 30 seconds, pressing the edges, so it adheres well.
7. Tape the edges or use a see-through dressing if it loosens.
8. If a patch falls off early, dispose of it, apply a new one, keep the original dosing schedule, and tell the physician or pharmacist.
9. Wash your hands with water right after applying.
10. At each change, use a different skin area.
11. Fold the used patch sticky-sides together and dispose of it properly.

Nursing Considerations

1. Pick a site that adheres well: clean, dry, hair-free, no sweat or cuts.
2. Rotate sites (upper arm, abdomen, hip) to limit irritation.
3. Mind skin thickness. Avoid skin that is very thin or very thick, which changes absorption.
4. Keep the patch dry, away from prolonged water or moisture.
5. Never apply a new patch over a previous site, which risks unintended interactions or overdosing.

Heat and Absorption: A Critical Safety Point

Heat speeds drug release and skin permeability, so an external heat source over a patch can push the dose dangerously high. With fentanyl patches this has caused fatal overdose. The FDA warns patients to keep the application site away from heating pads, electric blankets, heat or tanning lamps, saunas, hot tubs, heated waterbeds, and prolonged sun. A body temperature of 40 °C (104 °F) can raise serum fentanyl by roughly one-third on its own, so a febrile patient on an opioid patch needs closer watching (FDA). Teach patients to report fever and to avoid stacking heat on the site.

Accidental Exposure and Disposal

Used patches still hold enough drug to harm a child or pet, and accidental exposure to fentanyl patches has killed children (FDA). A patch that transfers to a child's skin or is mouthed can be fatal. Count patches on and off, confirm the old one comes off before a new one goes on, and fold each used patch sticky-sides together before disposal. Per FDA guidance, fentanyl and other dangerous opioid patches should be flushed if a drug take-back option is not available; follow the specific product label for disposal.

Frequently Asked Questions

How does a transdermal patch deliver medication? The patch holds the drug against the skin and releases it at a controlled rate. The drug crosses the stratum corneum, epidermis, and dermis into the capillaries, entering the bloodstream while bypassing the GI tract and first-pass liver metabolism.

Why does heat make a patch dangerous? Heat increases both drug release from the patch and skin permeability, so more drug enters the blood. With fentanyl, external heat or a high fever can raise serum levels enough to cause fatal overdose, so the site must stay away from heating pads, saunas, and direct sun (FDA).

What drugs are commonly given by patch? Fentanyl and buprenorphine for pain, nitroglycerin and clonidine for cardiovascular conditions, nicotine for smoking cessation, estrogen and testosterone for hormone therapy, rivastigmine and rotigotine for neurologic conditions, and selegiline for depression.

Where should a patch be applied, and should sites rotate? Apply to clean, dry, hair-free skin on the upper chest, upper outer arm, lower abdomen, or hip, following the product label. Rotate to a new area at each change to limit skin irritation and keep absorption consistent.

How do you safely remove and dispose of a used patch? Remove the old patch before applying a new one, fold it sticky-sides together, and dispose of it so children and pets cannot reach it. Used opioid patches still contain drug and have killed children through accidental exposure; flush fentanyl patches if no take-back program is available (FDA).

What should I do if a patch falls off early? Dispose of it properly, apply a new patch to a different clean site, keep the original dosing schedule, and notify the prescriber or pharmacist.