As yet there are no inhalable formulations of fentanyl on the market, but several are in development and in clinical trials. At the same time, other pain relief products are also moving into the increasingly fashionable area of inhalable drug delivery.

With the current pain relief market worth more than $25bn, the competition to come up with new and improved drug delivery systems is great. The fentanyl-based market alone is an estimated $2.5bn industry.

YM BioSciences' inhalable fentanyl, AeroLEF, is a proprietary formulation of free and liposome encapsulated fentanyl, which is administered by pulmonary inhalation for the treatment of moderate to severe pain. The free fentanyl is absorbed quickly with a rapid onset of pain relief, while the encapsulated fentanyl has an extended release.

The US-based company claimed the inhalable formulation was a step up from conventional formulations because the patient could determine their own drug dose.

Generally, because each patient has different pain relief needs, conventional pain relief is given in blocks until the desired effect is achieved, but the downfall is this takes time and can lead to potential overdosing.

Speaking to US-PharmaTechnologist.com, YM BioSciences investor relations spokesman James Smith said the idea with AeroLEF was patients could breathe in the amount of pain relief they felt they needed without having to rely on staggered drug administration.

"The current situation is hit and miss [in getting the right amount of pain relief to the patient first time]. This device is allowing the patient to decide what is the right amount. They have a faster feel of whether the pain is meeting their needs."

The system works by drawing in a breath of the AeroLEF. Because the free fentanyl is quickly absorbed and has a rapid effect the patient knows when a comfortable amount has been reached. The encapsulated fentanyl matches the amount of the free product to then provide extended pain relief.

"As far as we can see it stands out because it allows the patient to determine the right dose and very quickly."

When asked why an intranasal system, an increasingly popular choice for drug delivery, was not chosen, Smith said the lungs provided a greater surface area and quick transfer into the blood stream.

Being an opioid analgesic, with a potency 80 times that of morphine, there is always the consideration of drug abuse, but Smith said the system could be locked so the patient could not exceed a certain dose.

While the convenience of an inhaler promises to be an innovation in all forms of pain relief management, Smith said the fentanyl formulation would be used more in the hospital or clinical setting, though he acknowledged there was definitely a market for take-home pain relief.

Fentanyl is currently marketed as Duragesic by Janssen as a transdermal patch, and as Ionsys another transdermal device. Cephalon has marketed fentanyl citrate as Actiq, a solid formulation on a stick in the form of a lollipop that dissolves in the mouth, and last September launched Fentora an effervescent tablet placed in the cheek with the drug absorbed through the buccal mucosa.

Fentanyl has been an intravenous analgesic, marketed as Sublimaze, since the 1960s.

But as advances in drug delivery techniques develop, the door for innovation has blown wide open, and YM BioSciences is not alone in the future inhalable pain relief market.

Canadian drug-maker LAB International has an inhalable fentanyl in clinical trials, which is a fast-acting formulation delivered using the company's Taifun dry powder inhaler platform.

Meanwhile, Alexza Pharmaceuticals has developed its Staccato delivery system, which uses heat to quickly vaporize a drug to form a small particle aerosol which is inhaled, and is working on a fentanyl-based product.

Additionally, Nasalfent, an intranasal formulation of fentanyl, is in Phase III trials and BioDelivery Sciences has developed an oral adhesive disc inserted in the cheek to compete with Cephalon.

The IND submission to the FDA followed positive Phase II data and the company now plans to initiate an open-label Phase II trial designed to expand the target patient population and to meet with the FDA over the design of Phase III trials.