Related Experiment Videos
Dynamics of clarithromycin and azithromycin efficacies against experimental Haemophilus influenzae pulmonary
J D Alder1, P J Ewing, A M Nilius
1Experimental Therapeutics and Pharmacology, Abbott Laboratories, Abbott Park, Illinois, USA. alderj@bbott.com
Abstract:
The dynamics of clarithromycin and azithromycin efficacy against pulmonary Haemophilus influenzae infection in rats were evaluated. Efficacy was measured by reduction in pulmonary H. influenzae burden on days 3 and 7 postinoculation. Clarithromycin therapy was effective on day 3 or 7 of therapy, while azithromycin was effective on day 7 but not on day 3 of therapy. Both macrolides produced marked efficacy against all six strains of H. influenzae tested, including four strains for which MICs were above the susceptible breakpoint (8 microgram/ml) concentration of clarithromycin. The two macrolides demonstrated markedly different pharmacokinetic characteristics, with clarithromycin present in both blood and tissue, while azithromycin was concentrated primarily in tissue. During pulmonary infection in rats, H. influenzae was found in both intracellular locations and an extracellular location in the lung. Blood concentrations of clarithromycin and azithromycin approximated human pharmacokinetics, and the blood concentrations for either macrolide rarely exceeded MICs for H. influenzae. At dosages producing blood concentrations similar to values achieved clinically, clarithromycin produced efficacy on day 3 of therapy, while both clarithromycin and azithromycin were equally effective on day 7. The different dynamics of clarithromycin and azithromycin suggest that length of therapy should be considered as a key parameter in evaluations of drug efficacy.
Insights
Clarithromycin showed early efficacy against pulmonary Haemophilus influenzae in rats, while azithromycin
Area of Science:
- Pharmacology
- Microbiology
- Infectious Diseases
Background:
- Pulmonary infections caused by Haemophilus influenzae are a significant health concern.
- Macrolide antibiotics like clarithromycin and azithromycin are used to treat bacterial infections.
- Understanding the differential efficacy and pharmacokinetics of these antibiotics is crucial for effective treatment strategies.
Purpose of the Study:
- To evaluate the comparative efficacy of clarithromycin and azithromycin against pulmonary Haemophilus influenzae infection in a rat model.
- To investigate the impact of different therapy durations on the effectiveness of these macrolides.
- To correlate drug pharmacokinetics with observed treatment outcomes.
Main Methods:
- A rat model of pulmonary Haemophilus influenzae infection was established.
- Efficacy was assessed by quantifying the reduction in pulmonary bacterial burden on days 3 and 7 post-inoculation.
- Pharmacokinetic profiles of clarithromycin and azithromycin in blood and lung tissue were analyzed.
Main Results:
- Clarithromycin demonstrated efficacy by day 3 and day 7 of therapy.
- Azithromycin showed efficacy only by day 7, not on day 3.
- Both antibiotics were effective against all tested H. influenzae strains, including those with high minimum inhibitory concentrations (MICs).
- Clarithromycin exhibited distinct pharmacokinetic properties, with presence in both blood and tissue, unlike azithromycin, which concentrated mainly in tissue.
- At clinically relevant dosages, clarithromycin showed efficacy by day 3, while both agents were equally effective by day 7.
Conclusions:
- The duration of therapy is a critical factor in determining the efficacy of clarithromycin and azithromycin against pulmonary H. influenzae.
- Differences in pharmacokinetic profiles contribute to the varied dynamics of their effectiveness.
- These findings highlight the importance of considering both drug properties and treatment length in managing H. influenzae pulmonary infections.