Transdermal Patch Drug Delivery and Measurement Innovations

Medherant, a bioadhesives company formed as a spin-out from the University of Warwick (UK) in 2015, is developing its TEPI Patch technology, a higher-dosage drug-delivery patch with a constant rate of drug release. The patch is formulated by mixing the drug with an adhesive that enables high drug loading. The company’s first patch, containing ibuprofen, is being manufactured for clinical trials.

Dr. Gabit Nurumbetov, principal scientist at Medherant, has developed an improved instrument to test the release of drugs from a transdermal patch. The device, patented by Medherant, is an improved, miniaturized, and multiplexed version of a Franz or diffusion cell, which is a device commonly used to measure the amount of drug that permeates across human skin.

“In essence, the cell is a vial with a modified top part where you can place human skin and your formulation (gel, cream, or patch). The volume below the skin is filled with a biological fluid, which is taken out for analysis through a sampling port,” explains Nurumbetov. “The amount of drug permeated across the skin is then measured by means of chromatographic and/or spectroscopic methods allowing estimation of parameters such as API flux, patch area efficacy, and others.”

The improved diffusion cell, which is patented by Medherant, can test more than 100 formulations per day, compared to approximately 12 in the same period with traditional Franz cells, reports the company.

Drug release in a transdermal formulation is complex. “It is affected by physico-chemical properties of the adhesive and drug and the presence or absence of additional excipients in a formulation,” says Nurumbetov. “Some adhesives can chemically ‘hold’ drug molecules leading to a lesser amount of drug delivered. Also, if the molar mass of a drug is higher than 500 Daltons, it is likely to be not suitable for transdermal applications. Additional chemicals (permeation enhancers) in the formulation can also affect the drug-delivery performance.” The new instrument will allow high-throughput testing for faster development.