Study of the Prolonged Release of a Drug from Encapsulated Granules Prepared with Beeswax

The in vitro dissolution studies of encapsulated sodium salicylate granules coated with beeswax is presented. The factors investigated were the effects of concentration, presence of a hydrophilic fatty material, polyethylene glycol 6000 (PEG 6000), and technique (pan-coating, fusion and granulation) on the sustained release of drug when coated with beeswax. Comparison of release rates was based on the use of a parameter, t70% (time for 70% of drug to be released). The greater the concentration of beeswax, ranging from 13.04 to 28.75%, the more prolonged the release. The presence of PEG 6000 at a concentration of 1:9 beeswax in the coating fluid significantly (p<0.05) increased the release rate, and at a concentration of 1:1 nullified the sustained release effect of beeswax. The t70% for the fusion, granulated and pan-coated batches were in the increasing order of 25min., 1hr.35min. and 2hr.45min, respectively. INTRODUCTION: Prolonged release drug dosage forms have been found necessary in cases where a sustained action of the drug is needed over a specific time frame . The dosage form should be able to release the medicament in a controlled and predictable manner . Formulation methods include embedding or fusing the drug in a matrix, coating the drug by pan-coating, spray-congealing, spray-drying and coating of fine particles of drugs . The rate of release is evaluated by in vitro dissolution tests , and in vivo absorption measurements . However, in vitro data must be correlated with in vivo data . In their study, El-Sabbagh, et al.,, summarised that beeswax can be prepared as a mixture with the drug and it then functions as a time release mechanism, releasing the drug over a longer period of time. When beeswax was compared with carnauba wax, it was reported that both waxes retarded release of the drug after 12 hours and increased the time required for 50% drug release, but beeswax showed significant influence . The pan-coating technique has been successfully used in a slow-release study that made use of beeswax . A correlation between in vitro and in vivo data for sustained release delivery systems has been reported using acetaminophen as the drug . The aim of the present study is to determine three things, viz., the effect of various concentrations of beeswax on the release rate of the drug; the effect of the presence of a hydrophilic substance, such as Polyethylene Glycol 6000 on the retarding effect of beeswax; and the difference, if any, between the prolonging effects of beeswax on release rate when applied by pan-coating, fusion and granulation methods to the medicament.