ABSORPTION INTERACTIONS WITH FLUOROQUINOLONES - 1995 UPDATE

The utility of the fluoroquinolone class of antibiotics is rapidly exp anding due to their favourable pharmacokinetic profile and the continu ing development of new compounds. These agents are often used for indi cations not successfully treated with other orally available antimicro bials in the past, or for 'step-down' therapy in patients originally t reated with intravenous agents. As the usage of these agents expands f or serious systemic infections, knowledge of absorptive interactions w ith fluoroquinolones becomes paramount. Fluoroquinolones are often uti lised in dosages and against modestly susceptible pathogens which allo w a narrow margin for acceptable decreases in bioavailability. Chelati on interactions with multivalent cations can result in inactivation of the fluoroquinolone with ramifications in vitro and in vivo. Chelatio n interactions have been reported to occur in between 22 and 76% of pa tients prescribed fluoroquinolones. Concurrent administration of magne sium-aluminium antacids and sucralfate has the greatest effect on the bioavailability of quinolones followed by iron, calcium and zinc. Spac ing doses of fluoroquinolones and interactants has been suggested as a method of ensuring adequate quinolone absorption, but this can make o ptimal administration of the cation interactant difficult, if not impo sible.