Transdermal drugs are a vast category of drugs defined as vessels for the delivery of drugs for a local or systemic mechanism of action. Transdermal drug delivery has become increasingly popular due to the significant advantages they carry. For example, transdermal drugs bypass the firs-pass metabolism of the liver, protecting it from damage. Additionally, transdermal drugs decrease the risk of damage to the gastrointestinal system via the oral route, increase the likelihood of consistent patient use, and allows drug administration in a continuous stable-interval manner.
The fundamental principle of transdermal drug delivery relies on the ability of the drug to pass through the skin into the systemic circulation. Therefore, there are limited drugs that meet the criteria required to be able to bypass the skin. These criteria include having a low molecular weight (less than 600 g/mol), having the ability to pass through the epidermis, and being able to be absorbed by the blood vessels and enter the circulation. Additionally, the active drug must be chemically and physically stable, the active substance must have a low daily dose for patient comfort and adhesive propensity, and the skin should metabolize the drug. With such specific properties, there have only been a limited number of successful transdermal drugs.
Some indications that are addressed by transdermal medications since the 1970s include:
The greatest challenge for the success of transdermal drug delivery is diffusing active substances through the barrier function of the many layers of the skin. The outermost layer of the skin, the stratum corneum, is the thickest layer that includes numerous layers of keratin-heavy corneocytes. Additionally, the stratum corneum consists of two chemically different regions that need to be accounted for when creating transdermal drugs. There is an aqueous region at the outer surface of the keratin filaments and a lipid matrix between the filaments that active drugs need to have the ability to diffuse through both to be successful.
However, there have been recent advancements in the development of enhancement delivery methods for active drugs through the transdermal route. These methods are listed below:
Transdermal patches administration should follow a proper physical examination of patients and considerations of any associated comorbidities. The following steps are a general overview for administering a transdermal patch:
Administration of transdermal patches varies based on the drug administered via the patch. For example, a transdermal patch with 5% lidocaine for the treatment of pain involving conditions such as painful diabetic neuropathy, postherpetic neuralgia, etc. should follow these administration steps:
The main adverse effects that can be caused by transdermal drug delivery are skin reactions. Transdermal patches are the most common method of delivery for active substances. Transdermal patches can irritate the skin and cause pruritis, burns, and redness of the surrounding area. Additionally, there are reported allergic reactions for all types of patches on the skin due to the active substance administered. The two most common types of skin reactions include irritant contact dermatitis and allergic contact dermatitis, both of which are usually caused by the drug or the patch, including adhesives and excipients.
Transdermal drug delivery is contraindicated in patients with:
The most significant issue associated with transdermal drug delivery is the likelihood of skin irritation caused by penetration enhancement techniques and the transdermal patch itself. Due to this, there have been models created to foresee the likelihood of skin irritation due to drug or vessel interaction using solubility as well as skin irritation studies using the PII test for detection of redness or swelling 24 hours after administering the patch.
The toxicity of the transdermal patch depends on the selected drug/active substance administered through the use of transdermal drug delivery.
Managing proper drug administration in healthcare requires interprofessional effort from various healthcare professionals such as clinicians, pharmacists, nurses, residents, physician assistants, etc. Without appropriate regulation and administration techniques, numerous drug-related problems result in medication-related harm and low-quality healthcare for patients. To properly deliver a drug via transdermal patches, the following steps are necessary:
To enhance communication between healthcare professionals, techniques such as face-to-face interviews have proven to provide cohesiveness between pharmacists, primary care physicians, and surgical physicians for drug-related healthcare. Ultimately, these techniques allow for an amplified patient-centered approach.
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