Objective: It is important to ensure the quality of preparation in hospital pharmacies.  Therefore, we evaluated the quantitative method of preparation and the stability of allopurinol for external use in a new dosage form.
Methods: The new dosage form utilized two kinds of ointment, white petrolatum and hirudoid soft ointment, and liquid.  Allopurinol was extracted from these preparations by the liquid-liquid partition method, and assayed by high performance liquid chromatography.  A stability test was conducted for six months in the case of the ointments and one month in the case of the liquid.
Results: Good linearity was obtained, in the range of 30˜670 μg/mL (r²≥0.999).  The recovery of allopurinol added to the two kinds of ointment was 97.7-102.0%, and the relative standard deviation was less than 3.0%.  It was observed that the quantity remained relatively constant for one month, and increased after three months.
Conclusion: A quantitative method for the preparation of allopurinol in ointment, using white petrolatum and hirudoid soft ointment, was evaluated.  The results confirmed that allopurinol was stable for one month in ointment and liquid.