New oral macrolide and fluoroquinolone antibiotics: an overview of pharmacokinetics, interactions, and safety.

During the past decade, there has been a resurgence of interest in the development of oral macrolide and fluoroquinolone antimicrobial agents. Azithromycin and clarithromycin are two new oral macrolides whose pharmacokinetics (compared with those of erythromycin) are characterized by improved oral bioavailability, increased tissue penetration and persistence, and longer elimination half-lives. A limited number of interactions with other drugs have been reported for azithromycin and clarithromycin. The most common adverse reactions to the new macrolide agents include nausea, diarrhea, and abdominal pain. Norfloxacin, ciprofloxacin, ofloxacin, temafloxacin, and lomefloxacin are the oral fluoroquinolones that have been marketed in the United States thus far. In comparison to nalidixic acid, the newer fluoroquinolones have improved pharmacokinetic properties, including greater oral absorption, increased peak serum concentrations and areas under the curve, higher tissue concentrations, and longer elimination half-lives. Divalent or trivalent cations can alter the absorption of all fluoroquinolones. Some of the fluoroquinolones (norfloxacin, ciprofloxacin, and ofloxacin) can inhibit the cytochrome P-450 enzyme system and thereby cause increased serum concentrations of drugs like theophylline and caffeine. Adverse reactions to the fluoroquinolones primarily involve the gastrointestinal system, skin, and central nervous system.