Transdermal Patches

Products

Transdermal patches are approved as medicinal products. They offer themselves as an alternative to other modes of application such as peroral and parenteral administration. The first products were launched in the 1970s.

Structure and properties

Transdermal patches are flexible pharmaceutical preparations of varying sizes and thinness that contain one or more active ingredients. They are intended to be applied to uninjured skin to deliver the active ingredient into the bloodstream after passage through the skin barrier. Active ingredient patches with predominantly local effects are not considered transdermal patches. The two main types are matrix patches and reservoir systems:

  • Matrix patches: they contain a solid or semisolid matrix whose composition and structure determine the release. The matrix may contain self-adhesive components that allow it to adhere to the skin. Most transdermal patches today are matrix patches.
  • Reservoir patches: delivery rate is controlled using a semipermeable membrane. They are rarely used today.

An outer backing layer serves as a waterproof protective layer and covers the reservoir or matrix as an outer shell. The rate of delivery is proportional to the size of the patch in the matrix patches. The larger it is, the more active ingredient is released into the organism per unit time. Not all active ingredients are suitable for transdermal passage. As a rule, they should be lipophilic, have a small molecular mass and be effective at low doses. With appropriate excipients, such as DMSO, or with mechanical methods that compromise the integrity of the skin barrier, other and larger molecules may be able to be delivered.

Effects

Transdermal patches are applied to the skin and deliver their active ingredients continuously through the skin into the bloodstream. Effects occur with a time delay because plasma concentrations must first build up. Transdermal systems are therefore not suitable for acute therapy. Transdermal administration can be used to bypass first-pass metabolism, which is important, for example, for agents such as nitroglycerin or rotigotine. Transdermal patches are also suitable for active ingredients with a short half-life. The release from the patch is continuous and controlled and corresponds to a retardation. An up and down like when taking a fast disintegrating tablet is avoided. Thus, a flat and stable concentration profile is achieved and adverse effects due to concentration peaks can be avoided.

Indications for use

Transdermal patches have a variety of uses. Their indications include (selection):

  • Parkinson’s disease
  • Contraception
  • Alzheimer’s disease
  • Motion sickness
  • Angina pectoris and heart failure
  • Pain
  • Hormone replacement therapy
  • Smoking cessation
  • Hyperactive bladder
  • Nausea, vomiting
  • High blood pressure
  • ADHD

Dosage and application

According to the expert information and the package leaflet. Transdermal patches have a long dosing interval and need to be administered, for example, only once a day, every 72 hours, or even only once a week. They can be applied locally and, unlike peroral medications, do not need to be swallowed. Less frequent application can have a positive impact on treatment adherence. Drug delivery can be interrupted by removing the patch. Adhesion of the patch:

  • Apply the patches to a clean, completely dry, uninjured, flat, healthy skin area.
  • Do not use on reddened, irritated, diseased or injured skin.
  • Apply to a relatively hairless area. Do not shave directly before application (time interval at least three days). Otherwise, cut the hair with scissors.
  • Suitable skin sites include the buttocks, abdomen, the outside of the upper arm, back and torso (see technical information). Do not stick on the breasts.
  • Do not apply creams, lotions or powders on the skin site in advance, so as not to impair the adhesive properties.
  • Before sticking the protective film must be removed.
  • Do not touch the adhesive surface of the patch to avoid contact with the active ingredient.
  • After sticking, press the patch on the skin with the flat of your hand for about 30 seconds, so that it holds well.
  • Only one patch should be worn.
  • Do not write on the patch with a pen.

While wearing:

  • In the area of the patch do not apply direct heat (eg heating pad, hot baths, strong sunlight, solarium), so that is not increased active ingredient is released. Also in case of fever or intense sports can be released more active ingredient.
  • With a properly applied patch can be bathed and showered.
  • Regularly check whether the patch is still holding. If this is not the case, firmly press or additionally fasten with a medical fleece plaster. Or change the plaster (other skin site).

Patch change or end of therapy:

  • Before applying the new one, the old patch must first be removed.
  • Change skin site each time when applying a new patch (irritation, increased absorption).
  • Caution: the patch may still contain a lot of active ingredient after administration. Tape used patches together for disposal on the releasing area, place in a locked container and keep away from children. Wash hands afterwards. If mishandled, there is a risk of poisoning.
  • Remove patch residues on the skin with soap and water and not with organic solvents such as rubbing alcohol, so that no additional active ingredient is released.
  • Bring unused plasters back to the pharmacy.
  • The change can be made before the end of the dosing interval is reached, because the delivery is made at a constant rate.

Cutting transdermal patches.

Transdermal patches should not be cut up or otherwise manipulated. They are not intended for that purpose by the manufacturer (off-label use). Cutting poses a health risk and a legal risk. Reservoir patches are destroyed when cut. If there is a compelling need, the matrix patches can be cut. Gloves should be worn for this purpose. The remnants of the plaster should be disposed of. In the place where the patch was cut, it should be fixed to the skin with a fleece patch.

Agents

The following is a list of active ingredients that are administered using transdermal patches. Not all corresponding drugs are commercially available in many countries:

  • Buprenorphine (pain)
  • Clonidine (hypertension)
  • Estradiol, norethisterone acetate (hormone replacement therapy).
  • Fentanyl (pain therapy)
  • Granisetron (nausea and vomiting).
  • Methylphenidate (ADHD)
  • Nicotine (smoking cessation)
  • Nitroglycerin patch (angina pectoris)
  • Norelgestromin and ethinyl estradiol (contraception).
  • Oxybutynin (irritable bladder).
  • Rivastigmine (Alzheimer’s disease)
  • Rotigotine (Parkinson’s disease)
  • Scopolamine (motion sickness)
  • Selegiline (depression)
  • Testosterone (hypogonadism)

Adverse effects

Adverse effects depend on the active ingredients used. Transdermal patches may cause local skin reactions such as irritation, redness, itching, and allergic reactions. Digestive disorders, nausea and gastrointestinal irritation, on the other hand, do not occur or occur less frequently with transdermal patches because the active ingredient does not enter the gastrointestinal tract. Application errors can lead to adverse effects and overdoses. Transdermal patches are less discreet because they are visible on the skin (e.g., contraceptive patches). Finally, they may detach from the skin under certain circumstances.