[Microbiological purity of pharmaceutical preparation. Part 1: External remedies; and effects of type of cream, container, storage, temperature and application (author's transl)].

A fractional factorial experiment of the 2n type was carried out, to follow the effects of eight factors affecting simultaneously the microbiological purity of creams (Oleocremor leniens, Hydrocremor stearini) during the manufacturer-consumer chain. The effects of these factors (antibacterial substances, container (collapsible tube, pot), type of cream, storage (open, closed), number of takeouts, manner of taking-out (spatula, finger), temperature of storage, consumer (dermatological clinic, household) and interactive and interdependent. The microbiological purity of the creams is mostly impaired by the number of take-outs and the manner of taking-out. Collapsible tubes and, perhaps even better, one-dose packings are considered a solution of this problem. It is recommended to investigate creams individually with reference to their composition and structure, contents of antibacterial substances, technology and application. The tentative specification for the microbiological purity criteria of ointments and creams, designed for the Czechoslovak Pharmacopoeia, 4th Edition, is acceptable.