Comments on "Nebulised fentanyl for post operative pain relief, a prospective double blind controlled randomised clinical trial"

In our studies, two different novel proprietary aerosol generators delivered a single dose of the opioid (fentanyl base (100 μg, 50 μL chlorofluorocarbon propellant; morphine sulphate 1.1 mg, 44 μL aqueous solvent) into a single inspiration, followed by a standardised breath-hold before expiration. The risk with less control of administration is that the aerosol particles are larger and slower moving, and thus do not reach the alveoli in sufficient proportions, instead simply coating the mucosal surfaces of the oro-pharynx and respiratory tract from whence topical absorption occurs much more slowly than from the alveoli, and with some of the dose being swallowed with much smaller bioavailability. [...]both the amount and the rate of bioavailability, which are the critical factors for any drug and especially with aerosolised pulmonary administration, are very sensitive to experimental variables.