Production of an antibiotic coating on a porous body comprises impregnation with a solution of gentamicin dodecyl sulfate or sulfonate (I) and evaporation of the solvent where (I) has 1-5 dodecyl sulfate or sulfonate groups per gentamicin molecule. Independent claims are also included for (1) a process for producing an antibiotic coating on a porous body comprising impregnation with a solution of ciprofloxacin or moxifloxacin dodecylbenzyl sulfonate ciprofloxacin or moxifloxacin dodecyl sulfate ...