transdermal infusion system

transdermal infusion system

A method of delivering medicine by placing it in a special gel-like matrix that is applied to the skin. Each application will provide medicine for from one to several days. Nitroglycerin, fentanyl, lidocaine, estradiol, testosterone, and scopolamine may be administered through the skin. A transdermal drug patch has three key elements: a backing, the drug, and a liner that is peeled away before application. The absorption, delivery rate, and biodistribution of the drug are not affected by the patient's skin texture, thickness, or color. Drugs are equally well absorbed when applied to arms, thighs, back, or abdomen because various body sites have about the same rate of dermal penetration. When placed on intact skin, a transdermal drug patch creates a concentration gradient between the high concentration of drug in the patch and the low concentration in the skin. The drug then diffuses passively across the outermost skin layer (stratum corneum) into epidermal capillaries. Also called transdermal drug-delivery system.

Patient care

The skin acts as a reservoir for the absorbed drug; therefore simple removal of a patch does not stop release of the drug into the bloodstream. Patients may forget to tell health care providers that they are wearing a patch, or the patch may be overlooked because of its transparency or because of skin folds, and as a result the patient could receive an overdose if a similar drug is administered by another route. Thus, health care professionals should ask specifically about patch use when taking a patient's medication history. Most patches are imprinted with the drug name, dose, and release rate, providing needed information to the care provider. The patient should be taught to keep each patch in its protective wrapper until ready for use, to inspect it for leakage, and not to use it if it is damaged. If a patch leaks on the skin, the exposed skin should be thoroughly rinsed with water (soap should not be used because it can irritate the drug-exposed skin). The manufacturer's directions for patch application should be followed. Skin that is very hairy, oily, sunburned, scarred, calloused, or damaged; areas that tend to be sweaty; areas prone to friction (e.g., under a bra strap or at the waist line); and bony areas (e.g., the shoulders and hips) should be avoided. Skin should be clean and dry before the patch is applied, and powder, lotion, or residual oil from bath products or sunscreens should be removed by washing with mild soap and water and rinsing thoroughly. The drug name, dose, and delivery rate should be checked before the patch is applied. The patient should then peel off the protective liner and apply the adhesive side of the patch to the skin at the selected site, pressing the patch on firmly so that it adheres well, esp. around the edges. The hands should be washed immediately after applying a patch. Directions for removing a patch should be followed and the patch disposed of according to the manufacturer's instructions. Application sites should be rotated to avoid skin irritation. Depending on the particular drug and the prescribed regimen, a patch may be worn continually or removed for a portion of each day. Transdermal patches are best stored in their original container at room temperature with nothing stacked on top of them so as to protect them from excessive heat or pressure. If the interval between patch changes is lengthy, the patient must develop a system to assist in correctly scheduling the change. If a patient forgets to change a patch at the prescribed interval, he or she should remove the missed patch and apply a new one as soon as the error is discovered. Drug patches are waterproof, and the patient can bathe, shower, or swim while wearing a patch as long as it is not rubbed. If a patch starts to peel because of sweating, immersion in water, or hot, humid weather, it should be replaced, never taped to the skin, or held in place or covered in any way. Patch adhesive can irritate sensitive skin, but the reaction usually subsides when the patch is removed. Localized skin reactions may require treatment with a topical corticosteroid, but they should be reported to the primary care provider to determine the appropriate action.


1. Patients should remove a patch before having a magnetic resonance imaging (MRI) scan and replace it afterward with a new patch. The foil backing on many patches can cause MRI-related burns. 2. Patches containing estrogen or nicotine should not be applied to the breasts.
See: Transdermal Medications
Medical Dictionary, © 2009 Farlex and Partners
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