Various spray-congealed SETD-wax products were prepared by pneumatic atomization using six waxes (white wax USP, glyceryl tristearate, carnauba wax, hydrogenated castor oil, cetyl alcohol NF, and glyceryl monostearate), two nozzle sizes, 0.20 and 0.2 5 cm. (0.08 and 0.10 in.) i.d., and three concentrations of the surfactant sorbitan monostearate (0.1, and 5 percent w/w). The geometric mean diameters and the volume-surface diameters were affected primarily by the wax and the nozzle size used. All of the main effects, i.e., wax, nozzle size, and concentration of surfactant, had a significant effect on the percent of SETD released in acid pepsin and alkaline pancreatin media. In general, the dissolution rate increased as the concentration of surfactant was increased. Faster dissolution rates were noted with formulations atomized through the smaller of the two nozzles. The most important factor that had an effect on the dissolution behavior of these products was the wax used in a particular formulation. This effect depends upon the following factors: the physical properties of the wax and the drug-wax particles, the chemical composition of wax, and the composition of the dissolution medium.
HE USE of spray-congealing techniques for
T modifying the physical, chemical, or physiological behavior of drugs has gained increasing attention within recent years. This process has proved to be an effective means of controlling the particle size of drug-wax particles. Therefore, spray congealing may be quite useful in controlling the dissolution behavior of drugs intended for prolonged-release medication.
In 1958, the utilization of this process was reported for the first time in the pharmaceutical literature (1). A sustained-release powder of sulfamethylthiadiazole (SMTD) was prepared by mixing the drug with molten hydrogenated castor oil and atomizing the resulting suspension.
The same workers prepared a sustained-release powder of sulfaethylthiadiazole (SETD) by spray congealing a suspension of the drug using a centrifugal wheel atomizer (2). Spray congealing has also been employed by others for enhancing the stability and palatability of such compounds as iron salts, vitamin A, and the B vitamins (3-7).
Scott et al. ( 8 ) ,
were probably the first pharma-