Drug-Loss in Dispensing Process and Adhering to the Package : Phenytoin Products as Model Dosage Forms

The bioavailability of phenytoin is well known to be dependent on the dosage forms as is the fact that ground tablets of phenytoin are often ordered instead of the powdered form in doctorwritten prescriptions. Studied in the present study was weight loss of the drug resulting from the dispensing process and adherence to the package.Used as model forms were three dosage forms of phenytoin: ground tablets, fine granules and powder. Simulative dispensing was performed using the conventional method in which tablets were ground with excipients, mixed with a mortar and pestle, and divided and packaged employing two kinds of packaging machines for dispensing.The extent of total weight in loss was dependent neither on the types of packaging machines, nor on the dosage forms of phenytoin except for ground tablets. For ground tablets, a large weight loss was observed in the dispensing process, with this phenomenon being caused by splashing in the packaging process. Observed with fine granules and powder was a small weight loss relative to the dispensing process and a large one involving adherence to the package. The total loss in dispensing and package adherence was found to be 6% regardless of the phenytoin dosage form.We conclude that fine granules in the powdered form of phenytoin are the most suitable dosage form because of the compositis equivalent bioavailability to the tablet form and its only slight loss in weight during the dispensing process.