Pharmacologic particularities of antibiotics in cystic fibrosis

Antibiotherapy is one of the main treatment in cystic fibrosis. Antibiotic administration schedules are different from normal patients because of phar macokinetic and pharmacodynamic particularities. In moderate disease, the d igestive resorption of antibiotics is delayed and their half-life is reduce d due to an increase in total clearance. In severe disease, the volume of d istribution of antibiotics is increased due to the higher proportion of lea n mass in these malnourished patients. Other particularities limit the acti on of antibiotics such as thick sputum, which limits drug penetration; the property of Pseudomonas aeruginosa to be surrounded by a biofilm; alteratio n of local antibacterial defense; and inhibition of antibiotics by local fa ctors, Systematic prescription of a bitherapy beta-lactam-aminoglycosid and obtaining high antibiotic concentration in situ might limit this antagonis m. In spite of particular therapeutic schedules such as single daily dose f or aminoglycosid and continuous infusion for beta-lactams, the intervals be tween administrations must be narrowed for time-dependent antibiotics and t he total daily dose increased by 20 to 30% for concentration-dependent anti biotics. (C) 2000 Editions scientifiques et medicales Elsevier SAS.