Primary microparticles and agglomerates of morphine for nasal insufflation

The aim of this work was to study the characteristics of powders of morphine HCl suitable for nasal administration to be employed for pain treatment as alternative to injection. Primary microparticles of morphine were prepared by spray drying of aqueous drug solutions using sugars or sugar derivatives as drying protectors and particle shapers. The spray drying procedure modified morphine crystallinity making the substance amorphous and affecting its stability in dependence on the excipient employed. A tendency of the spray-dried powders to turn to varying degrees of yellow was observed. Tumbling the powder in a rotating pan allowed the agglomeration of the primary microparticles. Agglomerates were also obtained by tumbling a mixture of morphine crystals and spray-dried microparticles of excipients, with advantages for the stability of the preparation. A nasal device quantitatively insufflated all the morphine agglomerates. The in vitro transport of morphine through rabbit nasal mucosa was faster using nasal powders than with the saturated solution of morphine. Lactose was the most effective excipient for agglomerate manufacturing and delivery of spray-dried morphine. The agglomerates of morphine crystals mixed with mannitol/lecithin microparticles showed superior stability. However, the drug permeation through rabbit mucosa was slower than with spray-dried morphine microparticle agglomerates.