Particulate matter in reconstituted amphotericin B and assay of filtered solutions of amphotericin B.

Amphotericin B colloidal solutions were prepared according to the manufacturer's directions and filtered with membrane filters of different porosity to test for particulate matter; and the concentration and in vitro microbiological activity of filtered and nonfiltered solutions were determined. The amphotericin B solutions contained numerous particles. Filtration through 0.85- and 0.45-mum filters did not reduce the in vitro antimicrobial activity, and filtration through 5-, 0.45-, and 0.22-mum filters did not alter the concentration of the drug when assayed spectrophotometrically.