Transdermal patches are adhesive patches that doctors use to deliver medications to the human body. Patients place these patches on their skin and leave them there for several days. The patches have features that set them apart from other routes of administration, and they are effective for a variety of drugs.
Mechanism
Transdermal patches work in a fairly straightforward manner. One side of the adhesive patch contains medication. Patients place this side on their skin. The skin gradually absorbs the medication, which then enters the bloodstream. These patches release medications gradually, allowing patients to use them for several days at a time.
Advantages
Transdermal drug delivery systems have several advantages, explains Dr. Thomas Morrow in a 2004 article in "Managed Care Magazine." The patches are painless, do not require any injections and often allow doctors to reduce the dose of medication a patient needs to treat a medical condition. Transdermal patches are particularly useful for medications that are destroyed by stomach acid or are rapidly broken down by the liver because the medication can access the bloodstream without traveling through the stomach or liver. Bypassing the gastrointestinal tract also often reduces the side effects of a medication.
Disadvantages
Patients should be aware of risks associated with the use of transdermal patches. Broken or damaged patches may release the drugs they contain too quickly. The use of transdermal patches can also lead to errors in administering the patches, reports the Food and Drug Administration. Patients may forget when to apply a new patch or remove an old one. This confusion can result in patients receiving too much or too little of a medication. This risk is especially prevalent with patches that patients replace once every several days, because they or their caregivers must keep a record of when to administer each patch.
Considerations
To be effective, transdermal patches must be durable, comfortable and release a consistent amount of medication. These patches are evaluated in several ways, Pharma Info states. The uniformity of several different patches is checked---both for the purity and the quantity of the medication---to ensure that the drugs contained in multiple patches are approximately equal. Patches should also be strong, remain flat and not absorb large quantities of moisture.
Advances
The technology of transdermal patches is becoming more sophisticated, increasing the effectiveness of the patches. Some patches contain substances that improve the ease with which the skin absorbs a drug. These patches also have a mechanism that controls the timing and the amount of drug release, Morrow notes. Other patches contain miniature needles that inject medication through the patch without causing pain.
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