Incidence and resistant strains: The high incidence of acute otitis media and the frequency of resistant organisms involved in acute otitis media, particularly penicillin-resistant pneumococci have led investigators to search for alternative treatments. The choice of a suitable antibiotic therapy is based on antibacterial activities as well as on pharmacokinetic characteristics of the antibiotic to be used: the review deals with properties of ceftriaxone. Pharmacokinetics: Serum pharmacokinetis of this third generation cephalosporin diffen from that of all other cephalosporins: prolonged elimination half-life, dose dependent protein binding which results in progressively increased free drug reaching extravascular space. Kinetics of ceftriaxone in otitis media: in both experimental models of S. pneumoniae otitis media in the gerbil and in data in children and adults, antibiotic concentrations of fluid and mucosa of the middle ear have been high (up to 35 mg/l) and persistant for up to 48 hours after a 19 mg/l dose (in children). Pharmacodynamics of ceftriaxone in otitis media: The interpretation of experimental data is based on the definition of two pharmacodynamic parameters: - time above minimal inhibitory concentration (T > MIC90) which was 24 h in all experiments i.e. 100% between two doses; - inhibitory quotients (IQ) which were, even for the residual concentration at 24 hr, IQ = 35 or IR = 8.75 as a function of the MIC90 of ceftriaxone for S. pneumoniae, 1 mg/l or 4 mg/l respectively. A unique betalactam: Ceftriaxone is unique among betalactams as it offers a time above MICA of 100% for all pathogens involved in acute otitis media. These features confer upon this molecule a therapeutic role in acute otitis media, an indication of which it is already approved in France. (C) 1997, Masson, Paris.
