Accuracy in prescriptions compounded by pharmacy students.

Most compounded prescriptions are not analyzed to determine the accuracy of the employed instruments and procedures. The assumption is that the compounded prescription will be +/- 5% the labeled claim. Two classes of School of Pharmcacy students who received repeated instruction and supervision on proper compounding techniques and procedures were assessed to determine their accuracy of compounding a diphenhydramine hydrochloride prescription. After two attempts, only 62% to 68% of the students could compound the prescription within +/- 5% the labeled claim; but 84% to 96% could attain an accuracy of +/- 10%. The results suggest that an accuracy of +/- 10% labeled claim is the least variation a pharmacist can expect when extemporaneously compounding prescriptions.