| Description |
There exist two schools of thought regarding the preparation of ointments by fusion. Traditionally, authorities in the pharmaceutical field have general directed that the high melting point ingredients be melted first and the remaining ingredients added in order of their decreasing melting points so that the lower melting ingredients are not subjected to the temperatures required to melt the highest melting ingredient. Thomssen, however, in Modern Cosmetics, 3rd Edition, suggest that oils be heated first, and then the fats and waxes dissolved in the hot oils, so that by solution, rather than melting, the temperature can be kept below the melting point of the highest melting constituent. Further, other directions have been reduced to the simple expedient of melting all ingredients together simultaneously, a technique specifically discouraged by certain authorities. The purpose of this study was to examine these claims and to arrive at a method of preparation which would be the least time consuming and involve the lowest peak temperature during preparation of the ointment. White ointment was prepared from lump was by solution and fusion to test the thesis of Thomssen; by the traditional method as directed by the U.S.P.; and by melting the ingredients all together simultaneously. Since the results of these experiments tended to show advantages of time and temperature of the simultaneous method, the experiments were repeated using shredded was rather than lump was to see if the advantage of time and temperature might be artifacts resulting from the use of lump wax. Yellow ointment and an empirical cerate containing 30% white wax and 70% white petrolatum were then prepared by the traditional and the simultaneous methods to determine whether these advantages extended to other ointments or ointment-like preparations. Preparation time for white ointment by the method of Thomssen was too long to be practicable except in cases where one or more of the ingredients might be particularly heat sensitive and the heat sensitivity factor might be of greater importance than the time factor. Preparation of the ointment by the traditional method showed a peak temperature at the time of complete melting of the was which was several degrees higher than the upper limit of the melting range of white was as given by U.S.P. XV. This result is quite contrary to the stated objectives of proponents of the traditional method. Preparation by the simultaneous method resulted in a mean peak temperature only half a degree higher than the upper limit of the melting range of the wax, and occurred at the time of fusion of the ointment. Time of preparation was shorter by the simultaneous method. The experiments, repeated with shredded was rather than lump was, tend to pint up further the advantages shown for the simultaneous method. Preparation time and peak temperature were less in every case. However, the extra labor and time required to shred the wax must be considered. The preparation of yellow ointment and the cerate by the traditional and the simultaneous methods showed that the usefulness of the simultaneous method extends to other ointments manufactured by fusion. These results demonstrate that preparation time is less, and that substantially lower peak temperatures are encountered when the simultaneous methods of manufacture is used. Moreover, less labor is involved with the ingredients are added together at the beginning of preparation. Therefore it is suggest that the directions for compounding these ointments read, "melt the ingredients together simultaneously." |
