The competitive landscape in the transdermal drug delivery market covers two dimensions: (1) other microneedle manufacturers and (2) alternative technologies that could substitute for microneedles in delivering the same active ingredient. While the current front runner technology appears to be iontophoresis, it is unlikely that a single technology will dominate the market, as one may be better suited than the others for a particular application. Nevertheless, many of the devices currently in development are more costly and complicated compared to conventional passive patches. Indeed, the iontophoretic devices currently approved or on the market, all require the involvement of a healthcare professional, unlike the use of passive patches. In our view, the winning technology will be the one that clearly excels across the board in safety, efficacy, portability, user-friendliness, cost-effectiveness.

The very first microneedle systems, described in 1976, consisted of a drug reservoir and numerous projections (microneedles 50 mm to 100 mm in length) extending from the reservoir, which penetrated the stratum corneum and epidermis to the deliver the drug. Since then, thanks to the rapid advancement in microfabrication, there have been a number of developments in the design and cost of manufacture to make this system a viable approach to drug delivery.

Iontophoresis is the ability of an electric current to cause charges particles to move. In a patch form, two adjacent electrodes set up an electrical potential to drive charged compounds through the skin. This is particularly important for the transdermal delivery of peptides and oligonucleotides, due to the polar groups associated with these molecules. The real attraction of iontophoresis is that is does not rely on a concentration gradient and is not affected by individual differences in skin permeability. The technology also has the potential to deliver pulses, for example, hormonal treatments, simply by switching the current on or off.

This process uses high voltage pulses (~100 volts) and short treatment durations (milliseconds) to create transient permeable pores in the skin. Apparently electroporation disrupts the lipid bilayers in the stratum corneum and the channels it creates are said to promote the passage of hydrophilic drugs through the skin.

This technique involves the use of low frequency ultrasonic energy to enhance transdermal delivery of solutes either simultaneously or via pretreatment. The ultrasonic energy causes cavitation, or the production of extremely small bubbles in the skin that reportedly form small hydrophilic channels through the stratum corneum. These channels remain open for about 12 hours after the sound is turned off.

Heat increases skin permeation by increasing microcirculation and blood vessel permeability, which in turn facilitates drug transport into systemic circulation.

Using directed laser energy is another way to ablate the stratum corneum. As with microneedles, the ablated regions offer lower resistance to drug diffusion than non-ablated skin.

Radiofrequencies are another source of energy, which can be used to create highly localized microchannels in the skin.

Needleless jet injectors combine the advantage of transdermal and parenteral drug delivery methods. However, the technology does have a tainted history arising from some incidents about 20 years ago in which it was implicated in the spread of infection through cross contamination. While manufacturers have been re-engineered the devices to avoid contamination, it remains to be seen how quickly the market can overcome the past fears of this technology.

An older technology that is gaining renewed interest is the use of gels for the systemic delivery of drugs. The improvement of transdermal gel technology in the US in recent years is considered to be a significant advancement over passive patches due to its ease of use, delivery efficiency, cosmetic elegance, lack of irritancy associated with occlusion or adhesives, potential for in-house manufacture and the ability to apply drug to a large surface area. Their disadvantage lies in the inability to precisely control the dosing to each patient.