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Extending the residence time of drugs delivered to the lungs as inhalation aerosols may result in sustained therapeutic drug levels and reduced toxicity. Droplets were generated from 0.25 wt% disodium fluorescein (DF), and 0.25 wt% albuterol sulphate solutions at a rate of 1 ml min-1 using a Turbotac jet nebulizer. These droplets were dried, concentrated and mixed with saturated lauric acid (LA) vapor at bath temperatures of 60-140-degrees-C. The resulting coated particles were < 5 mum in size as estimated by inertial impaction and scanning electron microscopy. Powder composition, as determined by gas chromatography, ranged from ratios of 1.2:1 to 2.5:1, of LA: DF. Evidence of coating of DF by LA was derived from i.r. spectroscopy and X-ray microanalysis. Dissolution studies performed on the coated particles in phosphate buffer, pH 7.4 at 37-degrees-C and quantified by u.v. spectroscopy, showed that the half-time for dissolution (t1.2) increased from 4 +/- 2 min for uncoated DF particles, to 22 +/- 3-55 +/- 2 min for lauric acid coated DF particles, depending on the coating thickness. The t1/2 for albuterol sulphate particles increased from 2.5 +/- 1.5 min to 12.5 +/- 1.9 min for albuterol sulphate particles coated with lauric acid at a bath temperature of 100-degrees-C. Inhalation studies performed on beagle dogs with DF particles coated with lauric acid (bath temperature, 100-degrees-C) indicated there was a shift and broadening of the peak plasma concentration in comparison with aerosols of DF alone. The average absorption half-time increased from 4.7 +/- 0.8 min for uncoated DF particles to 11.5 +/- 1.6 min for lauric acid coated DF particles
