Tissue-directed pharmacokinetics
Article Abstract:
A review is presented of the pharmacokinetics of azithromycin, the first of a new class of antibiotics called azalides. The drug is active against many Gram-positive and Gram-negative microorganisms and penetrates cells better than macrolides (such as erythromycin), beta-lactams (penicillin) and quinolone antibiotics. Azithromycin also distributes over a larger area and has a longer half-life than these drugs. Because it enters tissues very well, a good measure of its activity is to use tissue levels, rather than the traditionally used blood levels. Azithromycin is quickly concentrated in several types of cells, including polymorphonuclear leukocytes, monocytes, alveolar macrophages, and fibroblasts. The kinetics of uptake into and release from these cells are explained. It is stable at low pH levels (acidic environments) and is 300 times more stable in the stomach than erythromycin. After a single oral dose, azithromycin has a bioavailability of 37 percent, compared with erythromycin's availability of 25 percent. It concentrates in tissues as much as 100 times more than it does in blood, and its particularly high concentrations in alveolar macrophages (in the lung) suggest that it could be important in this component of the body's defenses against infection. Based on pharmacokinetic parameters, a five-day, once-daily dosing should be adequate to treat many common infections. Azithromycin can be considered a 'tissue active' antibiotic whose efficacy is enhanced by delivery to tissues by phagocytes (scavenger cells). It is because of this property that azalide drugs have been said to create a new paradigm in antibiotic delivery. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1991
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The influence of age on the pharmacokinetics of temafloxacin
Article Abstract:
The effect of age on various parameters of how the antibiotic temafloxacin works in the body was analyzed in 12 elderly individuals, aged 73 to 89 years, and 12 younger individuals, aged 21 to 37 years. When orally administered, temafloxacin was rapidly absorbed into the blood in both age groups. The average blood level of the drug was 45 percent higher in the elderly compared with the young. The time that temafloxacin remained in the blood was also longer in the elderly, possibly indicating that the drug was slower in reaching the tissues. Essentially no difference was observed in the total time before the drug was eliminated from the body. Thus, the elderly do not need to be given a lower dose of temafloxacin. However, if the elderly have decreased functioning of the kidneys, a lower dose would be necessary, as the antibiotic would not be readily removed from the body and could cause adverse effects. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1991
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