In vitro antibacterial activity of the combination of clindamycin and ceftazidime

[Biological bases for the use of ceftazidime in anti-infection therapy]

The author presents the main in vitro and pharmacokinetic characteristics of ceftazidime, a third generation cephalosporin. Ceftazidime has been shown to be highly stable to most plasmid--or chromosome--mediated beta-lactamases. Several studies have demonstrated that its spectrum includes Gram-positive cocci as well as most Gram-negative bacilli, including beta-lactamase producers. Moreover, it has good in vitro activity against Gram-negative aerobic bacteria (Pseudomonas spp., Acinetobacter spp.) and frequently exerts a synergistic bactericidal action when combined with an aminoglycoside. As a result, ceftazidime displays a high intrinsic in vitro activity against most of the "difficult" strains. Pharmacokinetic studies indicate that ceftazidime exhibits metabolic stability in vivo; its elimination halflife is 1.8 hours, and about 88 to 92 p. 100 of the dose is recovered in the 24-h urine. Its extravascular distribution is excellent, with high levels being achieved in most tissues and body fluids in man. These in vitro and in vivo properties of ceftazidime suggest that this new cephalosporin should be considered a promising antibiotic for the treatment of severe infections.

Ceftazidime. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Ceftazidime is a new 'third generation' cephalosporin administered intravenously or intramuscularly. Similarly to other third generation cephalosporins it has a broad spectrum of in vitro activity against Gram-positive and Gram-negative aerobic bacteria, is particularly active against Enterobacteriaceae (including beta-lactamase-positive strains) and is resistant to hydrolysis by most beta-lactamases. Importantly, in vitro ceftazidime is presently the most active cephalosporin available against Pseudomonas aeruginosa, but it is less active against Staphylococcus aureus than first and second generation cephalosporins. Only larger comparative trials are likely to discern any statistically significant differences in clinical efficacy which may exist between ceftazidime and other antibiotics, but ceftazidime appears to be similar in efficacy to 'standard' comparative drugs in lower respiratory tract infections and complicated and/or chronic urinary tract infections among debilitated or hospitalised patients. Thus, in patients having Gram-negative infections at these sites and in whom the potential toxicity of the aminoglycosides is a concern, ceftazidime may be a valuable alternative in that it apparently lacks serious side effects and does not require routine drug plasma concentration monitoring. In fibrocystic patients having acute respiratory tract infections, ceftazidime is highly effective at both reducing symptoms of infection and temporarily reducing the sputum counts of Pseudomonas species. However, in these patients resistance to ceftazidime may develop, as seen with other beta-lactam antibiotics. In the treatment of fever of unknown origin or documented infections in immunocompromised adults and children, ceftazidime appears to be similar in efficacy to various 2- or 3-drug combinations. Nevertheless, the coadministration of an antibiotic having greater efficacy against Gram-positive bacteria should be considered in immunocompromised patients. Results from a small number of comparative trials suggest that ceftazidime may be as effective as the aminoglycosides in intra-abdominal, obstetric and gynaecological, and skin and soft tissue infections. However, further clinical experience, particularly a few well designed comparative studies, is needed to clarify the comparative efficacy in these conditions as well as in septicaemia/bacteraemia, meningitis, and bone and joint infections.