A description is given of a process for the preparation of a pharmaceutical composition of a macrolide antibiotic in essentially noncrystalline form, in which the macrolide antibiotic, a water-swellable polymer and a proton donor are blended in an extruder in the presence of water and forced through a die, the ratio by weight of the sum of macrolide antibiotic, water-swellable polymer and proton donor to water being at least 1:1. The macrolide antibiotic is preferably clarithromycin and the water-swellable polymer is preferably chosen from crosslinked polyvinylpyrrolidone, crosslinked sodium carboxymethylcellulose and crosslinked polyacrylic acid.
