The reliability of the preparation procedure for sphingosomal vincristine was studied. The effect of minor variations in the constitution conditions on the integrity of the drug product was also examined.
Two studies were conducted. The laboratory study, which had two parts, was conducted to determine the effects of deliberately varying the constitution conditions, including such key parameters as incubation time and incubation temperature. In the field study, 20 pharmacists unfamiliar with sphingosomal vincristine were asked to constitute the product using the written instructions provided in the package insert as their sole guidance. All samples in both studies were evaluated by measuring key product characteristics, including free (un-encapsulated) vincristine sulfate, total vincristine sulfate, vincristine degradation products, and in vitro release rate. Vincristine loading into sphingosomes was considered acceptable if the percentage of free vincristine sulfate did not exceed 10%.
In the laboratory study, samples that were incubated at 60-75 degrees C for 5-60 minutes met all the acceptance criteria. However, acceptable loading was not achieved for samples that were incubated at 55 degrees C for 10 minutes or less. In the field study, all the pharmacist-prepared samples met the acceptance criteria, with the results for free vincristine sulfate demonstrating a high degree of statistical confidence in the reliability of the loading procedure.
The recommended constitution procedure of sphingosomal vincristine from a three-vial kit can be reliably performed in pharmacies with a high degree of confidence. Small variations in temperature and incubation time had no effects on the quality of the product.