Use of a compound of formula (I): wherein the symbol cyclodextrin ]n represents a n-valent residue derived from a cyclodextrin compound by removing n of its hydroxyl groups; n is a number greater than 0 and represents the average number of substituents of formula per molecule of said compound; h is 0 or 1; R1 is a di-valent group selected from alkylene, hydroxy alkylene, halogeno alkylene, monocyclic aralkylene, cycloalkylene and phenylene; R2, R3 and R4 are each independently of one another a group selected from alkyl, cycloalkyl, aryl, aralkyl, and cycloheteryl; Xm− is a m-fold negatively charged anion; m is an integer being equal or greater than 1; and k is n/m in the preparation of an anti-infective medicament, as preservative and penetration enhancer.