Double-labelling technique in the evaluation of nasal mucoadhesion of disodium cromoglycate microspheres

99m Tc-labelled disodium cromoglycate particles and 111 In-labelled microspheres of disodium cromoglycate and polyacrylic acid were administered simultaneously to the nasal cavities of four healthy volunteers. The initial deposition patterns of the inhaled powder mixture as well as the drug removal due to the mucociliary clearance were monitored by a gamma camera. The double-labelling technique enabled in vivo comparison of simultaneously administered plain drug particles and polyacrylic acid microspheres of disodium cromoglycate. After administration, both the plain drug particles and the microspheres distributed equally effectively. On average, 27% of the 99m Tc-labelled plain drug particles and 50% of the 111 In-labelled microspheres were retained at the initial site of deposition 30 min after inhalation. Thus, the removal of microspheres from the nasal cavities was clearly impeded by polyacrylic acid.