Delivery Methods: The Patch Versus the Oral Route

Medication administration remains the hallmark of medication therapy. A general goal of pharmacotherapy is to ensure a therapeutic drug concentration in specific areas of the body or throughout the body. Among the various routes of administration, 2 emerge as competing choices for clinical use: oral administration and topical administration.

Oral administration remains the most commonly used route for medication. An oral medication generally becomes active when it passes from the gastrointestinal tract and the liver into the blood.1 Most newly approved medications are developed in oral forms to improve patient access and adherence, especially for oncology-related medications. The Table¹ identifies the most common oral dosage forms.¹

Topical administration allows drug absorption at specific areas of the skin, thereby limiting systemic absorption. Systemic absorption varies based on factors such as the site of application, the area of the skin, and the specific medication.² Among the various forms of topical administration, transdermal administration remains innovative and historically safe.

Transdermal administration delivers medication through the skin via patches or other delivery systems.^1-4 Although comparable to oral-dosage forms in efficacy, transdermal patches have numerous advantages over oral forms. First, transdermal administration avoids the first-pass effect of metabolism associated with the oral route. Therefore, transdermal administration allows for improved bioavailability. Second, transdermal administration allows prolonged release of certain medications, which can improve patient adherence. Third, transdermal administration minimizes adverse effects due to lower drug peak concentrations.^2,3

Although transdermal administration appears promising compared with the oral route, the mechanics of transdermal administration are not compatible with all medications.² For example, transdermal administration requires a medication to be hydrophobic; therefore, hydrophilic medications theoretically would not absorb well transdermally, which is an issue when systemic absorption is desired.^2-4

Some researchers have tried to determine whether the oral route or the transdermal patch is superior.^5,6 To evaluate the risk of vascular events in postmenopausal women, Mohammed et al conducted a systematic review of 15 observational studies of 28,160 women who received either oral or transdermal therapy.⁴ Overall, the researchers found that oral estrogen therapy was associated with a 66% higher risk of venous thromboembolism (VTE) and a 109% higher risk of deep vein thrombosis (DVT) compared with use of the transdermal patch in 11 studies.⁵ A major limitation of this finding is the observational studies themselves: such studies cannot account for all possible confounding factors. This suggests that transdermal estrogen therapy may be safer than oral estrogen therapy, especially in patients at risk for DVT or VTE.

Da Costa et al also conducted a systematic review of 22 randomized controlled trials of 8275 patients to evaluate the effects on pain and the safety of oral and transdermal opioids versus placebo. The researchers found there was not a significant difference between oral and transdermal opioids in improving pain in patients.⁶ The transdermal patch remains a compelling treatment alternative to oral administration for certain disease states, and research on the safety and efficacy of transdermal formulations of oral medications is ongoing.

Mohamed Jalloh, PharmD, is an assistant professor at Touro University in Vallejo, California, and a community pharmacist at Walgreens.

References

• Drug absorption, distribution, and elimination pharmacokinetics. Columbia Medicine website. columbia.edu/itc/gsas/g9600/2004/GrazianoReadings/Drugabs.pdf. Accessed June 6, 2016.
• Prausnitz MR, Langer R. Transdermal drug delivery. Nat Biotechnol. 2008;26(11):1261-1268. doi: 10.1038/nbt.1504.
• Kaestli LZ, Wasilewski-Rasca AF, Bonnabry P, Vogt-Ferrier N. Use of transdermal drug formulations in the elderly. Drugs Aging. 2008;25(4):269-280.
• Paudel KS, Milewski M, Swadley CL, Brogden NK, Ghosh P, Stinchcomb AL. Challenges and opportunities in dermal/transdermal delivery. Ther Deliv. 2010;1(1):109-131.
• Mohammed K, Abu Dabrh AM, Benkhadra K, et al. Oral vs transdermal estrogen therapy and vascular events: a systematic review and meta-analysis. J Clin Endocrinol Metab. 2015;100(11):4012-4020. doi: 10.1210/jc.2015-2237.
• Da Costa BR, Nüesch E, Kasteler R, et al. Oral or transdermal opioids for osteoarthritis of the knee or hip. Cochrane Database Syst Rev. 2014;9:CD003115.