ROUTINE PYROGEN TESTING
1 The examination of preparations from large‐scale manufacture for freedom from pyrogens is described. 2 Typical results from the examination of 11. and 0·51. packs of water for injection, glucose‐saline and solution and normal saline solution are presented. 3 Evidence supporting the claim that reduction in the pyrogen levels take place on storage is provided.
SOME OBSERVATIONS ON THE B.P. AND U.S.P. TESTS FOR PYROGENS
THE B.P. and U.S.P. tests for pyrogens depend on the temperature response of rabbits to intravenous administration of the test material. The methods of interpreting the data differ in the two tests but, in each, the material fails to pass the test if it produces a temperature rise greater than that prescribed. The maximum permissible response, in both the B.P. and the U.S.P., is a specified temperature rise, which is not related to any comparison with a standard preparation. Therefore, any factor which affects the magnitude of the temperature response will affect the sensitivity of the tests. The writer has already shown that the degree of restraint imposed on the rabbits, the type of thermometer used, and the frequency of administration of pyrogen, all affect the magnitude of the rabbit’s temperature response to bacterial pyrogenl. Thus when the degree of restraint imposed on the rabbits is severe and clinical thermometers are used, the magnitude of the response to pyrogens is much less than when the degree of restraint is slight and electrical thermometers are used. Furthermore, there is a progressive reduction in response when pyrogen is given repeatedly. The B.P. and U.S.P. specify neither the degree of restraint nor the type of thermometer to be used. Both pharmacopceias permit the repeated use of the same animals. Two questions of practical importance arise from these considerations. The first and more obvious is; how far may the reliability of the tests be affected by failure to take these sources of variation into account? The second, which derives from the different methods of interpreting the data in the B.P. and U.S.P. tests, is; how do the relative efficiencies of the two tests compare when conducted in similar conditions? This paper seeks to provide an answer to these two questions.
A new method of near field analysis
The problem of the accurate determination of the total electromagnetic field produced by a current distribution on a circular disc type aperture is examined. For comparison of the near and Fresnel region solutions, an exact Maxwellian integral is used as the starting point. Aperture and space coordinates are separated by the use of Bessel function addition theorems, allowing the field to be expressed as a sum of terms containing radial and angular integrals. The radial integrals involve only the disc (aperture) distribution and coordinates while the angular integrals involve only the elevation angle. The distance from origin appears implicitly in the series coefficients. These integrals are suitable for high speed computations and have been evaluated for a number of cases. The results are compared with the small angle and general Fresnel formula values for various observation angles, distances from the aperture, and aperture distributions.