Penetration of antimicrobial agents into bronchial secretions

The Pharmacology of Aminoglycosides—I. Considered as a Group

This review of aminoglycoside pharmacology will appear in two parts. The first segment summarizes general information applicable to all agents, such as aspects of absorption, distribution, and clearance. The subsequent article will focus on specific agents currently in use in clinical practice: gentamicin, tobramycin, netilmicin, amikacin, streptomycin, and kanamycin, highlighting toxicities and pharmacokinetic-based dosing strategies.

Embedded in the history of antimicrobial agents with the discovery of streptomycin in 1944, the aminoglycosides remain a mainstay of contemporary antibiotic therapy. Noteworthy features include rapid bactericidal activity against aerobic gram-negative organisms as well as additive or synergistic activity when coadministered with beta-lactam agents. These positive attributes are offset by limited penetration into various body fluids and tissues, and dose (concentration) related renal and ototoxicity. Despite the proliferation of safer beta-lactam compounds with expanded antimicrobial spectrums, the aminoglycosides are still initial drugs of choice for most life-threatening, aerobic, gram-negative infections. Used in combination with anti-pseudomonal penicillins, the aminoglycosides are the agents of choice for empiric therapy of fever in the neutropenic host or documented tissue infection with Pseudomonas aeruginosa.

Advanced Techniques in the Diagnosis and Management of Infectious Pulmonary Diseases in Horses

Techniques for novel approaches to the diagnosis and management of equine pulmonary disease continue to be developed and used in clinical practice. Diagnostic techniques involving immunoassays and nucleic acid-based tests not only decrease the time in which results become available but increase the sensitivity and specificity of test results. These assays do not substitute for careful clinical evaluation but can shorten the time to a confirmed accurate diagnosis, and thus allow for early initiation of therapeutic strategies and prevention protocols. With further understanding of the molecular biology and immunology of equine pulmonary disease, diagnostic and management techniques should become further refined.

Antibiotic use in Cystic Fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the β-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Concentrations of gentamicin in serum and bronchial lavage fluid after once-daily aerosol administration to horses for seven days

OBJECTIVE

To assess gentamicin concentrations in serum and bronchial lavage fluid (BLF) of horses during a 24-hour period after once-daily aerosol administration of gentamicin (GAER) for 7 days and the pattern and degree of bronchial tree inflammation associated with repeated GAER.

ANIMALS

13 healthy adult horses (9 geldings and 4 mares).

PROCEDURE

The treatment group comprised 8 horses, and 5 horses were untreated control animals. Gentamicin (20 mL of gentamicin [50 mg/mL]) was administered via aerosol once daily for 7 days. Samples of serum and BLF were obtained from all horses before GAER and 0.5, 4, 8, and 24 hours after the final day of GAER. Gentamicin concentrations were determined for all samples from treated horses, and cytologic examinations were performed on all BLF samples.

RESULTS

Peak median BLF gentamicin concentration detected at 0.5 hours was 2.50 microg/mL. Median serum gentamicin concentration was < 0.50 microg/mL at all time points. Significant differences were not observed in total nucleated cell counts or differential cell counts in BLF between groups at any time point. Neutrophil count in BLF for all horses was increased over baseline at 4 and 24 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

We did not detect evidence of gentamicin accumulation or respiratory inflammation after once-daily GAER for 7 days. This protocol appears unlikely to result in local or systemic toxicosis. Repeated daily GAER to horses appears to be a safe procedure and may have clinical use in the treatment of horses with bacterial infections of the airways.

Morphostructural damage and the inhibition of bacterial adhesiveness of Staphylococcus aureus and Moraxella catarrhalis induced by moxifloxacin

The aim of this study was to investigate the ability of moxifloxacin to interfere with the mechanism of bacterial adhesion and disrupt the morphological and structural integrity of bacteria. Three Staphylococcus aureus and three Moraxella catarrhalis strains were grown in the presence of 1/2-1/128 minimum inhibitory concentration (MIC) serial dilutions and incubated with human epithelial cells. A significant decrease in adhesion was observed from 1/2 MIC to 1/64 MIC for S. aureus, and from 1/2 MIC to 1/16 MIC for M. catarrhalis. The use of atomic force microscopy, a new technique capable of revealing surface structures in three-dimensional detail and at very high resolution, showed the rapid onset and time course of the sequence of disruptive morphostructural events following the incubation of both S. aureus and M. catarrhalis with sub-MICs of moxifloxacin. Our findings suggest that less than conventional MIC moxifloxacin concentrations may be effective in reducing bacterial adhesiveness and structural integrity on which the maintenance of bacterial activity depends.

Concentrations of gentamicin in serum and bronchial lavage fluid after intravenous and aerosol administration of gentamicin to horses

OBJECTIVE

To compare concentrations of gentamicin in serum and bronchial lavage fluid after IV and aerosol administration of gentamicin to horses.

ANIMALS

9 healthy adult horses.

PROCEDURE

Gentamicin was administered by aerosolization (20 ml of gentamicin solution [50 mg/ml]) and IV injection (6.6 mg of gentamicin/kg of body weight) to each horse, with a minimum of 2 weeks between treatments. Samples of pulmonary epithelial lining fluid were collected by small volume (30 ml) bronchial lavage 0.5, 4, 8, and 24 hours after gentamicin administration. Serum samples were obtained at the same times. All samples were analyzed for gentamicin concentration, and cytologic examinations were performed on aliquots of bronchial lavage fluid collected at 0.5, 8, and 24 hours.

RESULTS

Gentamicin concentrations in bronchial lavage fluid were significantly greater 0.5, 4, and 8 hours after aerosol administration, whereas serum concentrations were significantly less at all times after aerosol administration, compared with IV administration. Neutrophil counts in bronchial lavage fluid increased from 0.5 to 24 hours, regardless of route of gentamicin administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Aerosol administration of gentamicin to healthy horses resulted in gentamicin concentrations in bronchial fluid that were significantly greater than those obtained after IV administration. A mild inflammatory cell response was associated with aerosol delivery of gentamicin and repeated bronchial lavage. Aerosol administration of gentamicin may have clinical use in the treatment of bacterial bronchopneumonia in horses.

Antimicrobial susceptibility of Bordetella bronchiseptica isolates from cats and a comparison of the agar dilution and E-test methods

One hundred and fifty-two predominantly feline isolates of Bordetella bronchiseptica were tested for their susceptibility to seven antimicrobial agents using an agar dilution method. The majority of isolates tested by the agar dilution method were resistant to trimethoprim (MIC90 500 micrograms/ml) and ampicillin (MIC90 > 32 micrograms/ml) but sensitive to tetracycline, doxycycline and enrofloxacin (MIC90 2 micrograms/ml for all three agents). The isolates showed a spectrum of susceptibility to sulphadiazine and clavulanate potentiated amoxycillin. The MIC's of twenty-nine of the 152 isolates were then compared for five of the antimicrobial agents using the E-test (AB Biodisk, Sweden), a recently introduced method for measuring the MIC's of antimicrobial agents based on the diffusion of a pre-defined antibiotic gradient from a plastic strip. Comparisons with the E-test demonstrated an overall agreement (+/- 1 log2 dilution) with the agar dilution method of 79.4% and an agreement within +/- 2 log2 dilutions of 96.2%.

Pharmacokinetics of antimicrobial agents in the respiratory tract

The ability of antibiotics to penetrate into the respiratory tract has been investigated at several sites, namely, sputum and bronchial secretions, tissue homogenates, pleural fluid and, more recently, epithelial lining fluid and alveolar macrophages. The major reason for such investigations is that these data may be helpful to a more thorough understanding of drug distribution in the lung tissue and fluids and to a more accurate prediction of clinical outcome. However, the study of drug concentration at each of these sites presents problems in terms of methodology and data interpretation. The advantages and disadvantages of each of these methods are considered, and the data on penetration of betalactams, aminoglycosides, macrolides, fluoroquinolones and other antimicrobial agents (including antifungal and antiprotozoan drugs) are reviewed.

Drug monitoring in nonconventional biological fluids and matrices

Determination of the concentration of drugs and metabolites in biological fluids or matrices other than blood or urine (most commonly used in laboratory testing) may be of interest in certain areas of drug concentration monitoring. Saliva is the only fluid which can be used successfully as a substitute for blood in therapeutic drug monitoring, while an individual's past history of medication, compliance and drug abuse, can be obtained from drug analysis of the hair or nails. Drug concentrations in the bile and faeces can account for excretion of drugs and metabolites other than by the renal route. Furthermore, it is important that certain matrices (tears, nails, cerebrospinal fluid, bronchial secretions, peritoneal fluid and interstitial fluid) are analysed, as these may reveal the presence of a drug at the site of action; others (fetal blood, amniotic fluid and breast milk) are useful for determining fetal and perinatal exposure to drugs. Finally, drug monitoring in fluids such as cervical mucus and seminal fluid can be associated with morpho-physiological modifications and genotoxic effects. Drug concentration measurement in nonconventional matrices and fluids, although sometimes expensive and difficult to carry out, should therefore be considered for inclusion in studies of the pharmacokinetics and pharmacodynamics of new drugs.

Effect of bromhexeine on sputum amoxycillin levels in lower respiratory infections

Bromhexeine has been widely used as an adjunct in the management of lower respiratory infections and is useful in altering the physical characteristics of sputum. Its effect on the sputum penetration of an antibiotic has been sparsely studied. The present study highlights the improvement in sputum amoxycillin (amoxy) levels when a combination tablet, amoxy 500 mg plus bromhexeine 8 mg, is administered as compared to plain amoxy 500 mg. Sputum amoxy levels were significantly higher in the combination group (0.674 +/- 0.588 micrograms ml-1) as compared to 0.272 +/- 0.19 micrograms ml-1 in the amoxy group (P = 0.028). The clinical responses assessed by the physician as well as the patient were significantly better in the amoxy plus bromhexeine group as compared to the amoxy group. The radiological and bacteriological responses were similar in both groups. There was no increase in the side-effects due to bromhexeine and, overall, its use can be recommended in the treatment of acute lower respiratory infections.

Drug treatment of pneumonia in the hospital. What are the choices?

Mortality and morbidity of nosocomial pneumonia remain high. Successful treatment of pulmonary infections depends on several factors including type of infection, offending pathogen, status of host defences, and adequate choice of antibiotic therapy. The physician's decision should aim at achieving antibiotic concentrations beyond the MIC at the site of infection. Gram-negative bacilli, notably Pseudomonos aeruginosa, Klebsiella pneumoniae and Escherichia coli, remain the most frequent agents in nosocomial pneumonia. Staphylococcus aureus and Streptococcus pneumoniae predominate among the Gram-positive cocci. Pneumocystis carinii predominates in immunocompromised patients. Protected sample bronchoscopy associated with quantitative cultures of samples, and quantification of intracellular microorganisms in cells recovered by broncho-alveolar lavage are two promising procedures which might replace previous, more aggressive methods. Penetration of antibiotics into lung tissue depends on physicochemical properties of the drug and the degree of inflammation of lung tissue. Quinolones, macrolides, tetracyclines and trimethoprim penetrate well into bronchial secretions. Penetration is moderate to low for aminoglycosides and beta-lactams. Fluoroquinolones and new beta-lactam agents, including third-generation cephalosporins imipenem, aztreonam and ticarcillin-clavulanate, showed comparative clinical efficacy in treatment of nosocomial pneumonia, with an efficacy rate close to 80%. Aminoglycosides should not be used alone. Combination therapy reduces but does not eliminate the risk of selection of Gram-negative resistant mutants. It should not be used routinely except for P. aeruginosa, Enterobacter cloacae and Serratia marcescens infections.

Penetration of ampicillin and sulbactam in the lower airways during respiratory infections

We studied the penetration of ampicillin-sulbactam in the alveolar lining fluid (ALF) of eight patients after intravenous administration of 2,000 mg of ampicillin and 1,000 mg of sulbactam three times daily over 30 min. Bronchoalveolar lavage was performed on day 3, 30 min after the end of the morning drug administration. The mean penetration ratios (i.e., the ratios of the concentrations in ALF versus those in serum) were 53% (standard error, 12%) and 61% (standard error 31%) for ampicillin and sulbactam, respectively. The concentration ratio of ampicillin versus sulbactam in serum was not significantly different from that in ALF. From a pharmacokinetic point of view, ampicillin-sulbactam is a good choice for treatment of infectious exacerbation of chronic obstructive pulmonary disease and community-acquired bacterial pneumonia, since the concentrations of both drugs in ALF exceed the MICs for the respiratory pathogens responsible.

Endotracheal tobramycin in gram-negative pneumonitis

This report describes the treatment of resistant gram-negative pneumonitis in a compromised host by the combined use of intravenous and endotracheal tobramycin. The endotracheal administration appeared to have an effect on the serum concentration and elimination rate, necessitating a reduction in the amount of drug given intravenously. The only apparent clinical complication of endotracheal drug administration was transient coughing. The addition of endotracheal aminoglycosides to intravenous antibiotics may be useful in pediatric patients with unresponsive (or other difficult-to-treat) pneumonitis caused by resistant microorganisms. The potential contribution of endotracheal aminoglycosides to the serum level and/or disposition profile must be recognized, and therapeutic drug monitoring guided accordingly when this route of administration is used.

Aminoglycoside antibiotics in clinical use

Aminoglycosides are among the most used antibiotics despite competitive pressure from newer beta-lactam agents. The activity profile, pharmacology, toxicity potential, and methods of toxicity prevention of aminoglycosides are well appreciated after three decades. Nephrotoxicity, ototoxicity, and the added costs of drug level monitoring limit wider usage, but great activity against highly antibiotic resistant gram negative bacteria often outweigh these disadvantages and will likely keep aminoglycosides available for the foreseeable future.

Vancomycin entry into lung lymph in sheep

The distribution of antibiotics into target tissues is a crucial factor in therapeutic efficacy. To estimate the availability of systemically administered vancomycin to the interstitial fluid in the lung, we have used a sheep model with a chronic pulmonary lymph fistula to collect simultaneously series of plasma and pulmonary lymph specimens during a 6-h period after an intravenous dose of vancomycin (7 mg/kg). After a minor delay in transit from blood to lymph, vancomycin was completely distributed to pulmonary lymph with a ratio of free drug in lymph to free drug in plasma of 0.9. This suggests that vancomycin is an excellent choice for treating pulmonary infections by susceptible organisms.

Susceptibility of Bordetella pertussis to five quinolone antimicrobic drugs

Five quinolone antimicrobic agents were tested to determine the mean inhibitory concentration (MIC) of each of 17 clinical strains of Bordetella pertussis by the agar dilution method. Ciprofloxacin demonstrated the best in vitro activity with an MIC90 of 0.06 microgram/ml. Norfloxacin, ofloxacin and enoxacin were also highly active with MIC90s of 0.25, 0.25, and 0.5, respectively. Cinoxacin was only moderately active (MIC90 4.0 microgram/ml).

Local treatment of respiratory infections with antibiotics

Local administration of antibiotics for the treatment of respiratory infections has the potential advantage of reduced systemic toxicity and increased drug concentration at the site of infection. This article reviews the basic principles of pulmonary drug delivery using aerosols and the clinical efficacy of local antibiotic therapy of respiratory infections. Clinical studies have been conducted with locally administered aminoglycosides, penicillins, cephalosporins, and polypeptides. The results of these investigations and the pharmacokinetic aspects of pulmonary antibiotic delivery are summarized.

Treatment of respiratory tract infections with cephalosporin antibiotics

Infections of the respiratory tract are among the most common causes for antibiotic prescribing. Their diagnosis within the community is generally limited to clinical criteria, and microbiological information is frequently lacking. Hospitalised patients with respiratory tract infections are more likely to undergo diagnostic sampling, but difficulties remain in reliably defining a microbial aetiology, thereby providing a confident basis for antibiotic selection. In considering the role of the cephalosporins in the treatment of respiratory tract infections, over 500 published articles have been reviewed. The pharmacokinetic considerations are discussed and the limitations of existing methodology are emphasised. Individual agents are reviewed by site of sepsis and conclusions are drawn from both comparative and non-comparative studies and in relation to currently recommended regimens. Although oral cephalosporins are widely used to treat upper respiratory tract infections, none is considered ideal, especially where Haemophilus influenzae is pathogenic. In the case of lower respiratory tract infections the beta-lactamase stable parenteral cephalosporins have become widely used to treat pneumonia in hospitalised patients, especially where Gram-negative enteric bacilli are of aetiological importance. However, the lack of activity of these drugs against Legionella spp., Mycoplasma pneumoniae and Coxiella burnetii must be emphasised. Another area of increasing use is in the treatment of infective exacerbations in patients suffering from cystic fibrosis of the lungs where Pseudomonas aeruginosa is pathogenic; ceftazidime in particular has proved a useful alternative to earlier antipseudomonal penicillin antibiotics.

Penetration and concentration of cefadroxil in sputum, lung and pleural fluid

The penetrability of cefadroxil in sputum, pleural fluid and lung tissue was examined in patients with acute respiratory infections, or who were undergoing thoracic surgery. The concentration of antibiotic in these tissues after single doses of 500 mg or 1 g was approximately half of that seen in serum, but persisted longer. In all biological matter studied, the concentration of cefadroxil was sufficient to inhibit pathogens such as S. aureus, S. pneumoniae and S. pyogenes, shown to be common causes of respiratory illnesses. Thus, cefadroxil should be a useful agent in the treatment of such infections.

Penetration of aztreonam into human bronchial secretions

Nine intubated patients were given a single, 2-g intravenous dose of aztreonam over 5 min. Samples of serum and bronchial secretion were obtained 2, 4, and 8 h after administration and assayed for aztreonam content. The mean concentrations in bronchial secretion ranged from 1.9 to 5.2 micrograms/ml and tended to be highest at 4 h. The concentrations in bronchial secretion varied from patient to patient, but each patient had one or more bronchial secretion samples that contained at least 2.7 micrograms of drug per ml.

Antibiotic use in cystic fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the beta-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Association of aminoglycoside plasma levels with therapeutic outcome in gram-negative pneumonia

To determine the association of aminoglycoside plasma levels with therapeutic outcome in gram-negative pneumonia, the case reports of 37 patients from four prospective, randomized, controlled trials of gentamicin, tobramycin, and amikacin were analyzed. Twenty (54 percent) of these patients had a favorable outcome. Patients with maximal one-hour postinfusion (peak) levels of 7 micrograms/ml or greater for gentamicin and tobramycin or 28 micrograms/ml or greater for amikacin more often had successful outcomes (14 of 20, 70 percent) than those with levels less than this (six of 19, 32 percent) (p less than 0.006). Patients with overall mean peak levels of 6 micrograms/ml or greater for gentamicin and tobramycin or 24 micrograms/ml or greater for amikacin more often had successful outcomes than those with levels less than this (six of 17, 35 percent) (p less than 0.04). The initial patient temperature, serum urea nitrogen/creatinine ratio, initial polymorphonuclear leukocyte count, and age were also associated with outcome; but by multivariate analysis, achieving an adequate peak concentration was the most important discriminating factor. These results suggest the potential importance of achieving adequate aminoglycoside levels in patients with gram-negative pneumonia.

Combination antimicrobial therapy

In spite of a large volume of data regarding the in vitro activity of single and combined antimicrobial activity, the clinical relevance of these studies is unclear. Few comparative trials of combined and single antibiotic therapy of human infection have been performed. Synergistic combination therapy has been shown to be beneficial in a few specific circumstances. Antagonistic combinations should be avoided in the treatment of meningitis, endocarditis, and infections of immunocompromised patients. The bactericidal titer of serum or spinal fluid should reflect adequacy of therapy of meningitis, endocarditis, and osteomyelitis, and adjustments can be made accordingly.

A review of the therapeutic efficacy of aerosolized and endotracheally instilled antibiotics

Achievement of sufficient concentrations of aerosolized antibiotic at the site of infection is limited by technical problems in antibiotic delivery and by drug inactivation. Antibiotic delivery by aerosolization is generally associated with minimal systemic absorption, whereas systemic absorption may be significant after endotracheal instillation. Methodologic problems make correlations between clinical response and sputum antibiotic concentrations difficult. Studies suggest that aerosolized antibiotics are of little value in the treatment of chronic bronchopulmonary infections. Endotracheal instillation appears to be associated with favorable clinical responses, possibly due to enhanced antibiotic delivery to the site of infection. Prophylactic aerosolized antibiotics are effective in altering sputum flora; reduction in mortality from acquired pneumonia has not been demonstrated. The development of resistant organisms may occur as a result of prophylactic treatment.

Comparative trial of cefonicid and cefamandole in the therapy of community-acquired pneumonia

Cefonicid (Smith Kline & French Laboratories; D-75073) is a new parenteral cephalosporin with a markedly long half-life, high serum levels, and good in vitro activity against Haemophilus influenzae. Patients with community-acquired pneumonia were randomized 2:1 to receive cefonicid, 1 g daily (21 cases) or cefamandole, 1 g every 6 h (12 cases). The two groups were similar, except that the cefonicid patients were older (mean 42 versus 31 years). Peak serum levels of cefonicid averaged 133 microgram/ml after intravenous and 83 microgram/ml after intramuscular administration compared with 55 microgram/ml with intravenous cefamandole. All 9 patients on intramuscular cefonicid and 8 or 12 patients on intravenous cefonicid had trough serum levels of greater than 2.0 microgram/ml at 24 h. Sputum levels of cefonicid were usually between 2.0 and 4.0 microgram/ml and did not correlate with serum levels. Cefonicid was well tolerated, and all cefonicid patients responded clinically. Sputum cultures for H. influenzae or Streptococcus pneumoniae became negative in 6 of 7 cefamandole patients and 13 or 15 cefonicid patients. In in vitro studies, cefonicid inhibited 90% of beta-lactamase-negative h. influenzae at 0.5 microgram/ml and beta-lactamase-positive strains at 2.0 microgram/ml. Cefonicid inhibited 50% of S. pneumoniae at 1.6 microgram/ml, but required 6.4 microgram/ml to inhibit 90%. Cefonicid once a day appears to be as safe and as effective as cefamandole four times a day for therapy of community-acquired pneumonia.

The aminoglycosides

Aminoglycosides remain the cornerstone of prophylaxis and therapy against the majority of aerobic gram-negative organisms responsible for serious sepsis in the hospital. Gentamicin, tobramycin, amikacin are all equally efficacious against susceptible organisms and differ only in their patterns of resistance and pharmacokinetic profiles. The ototoxic and nephrotoxic potential of gentamicin, tobramycin, and amikacin is comparable. Amikacin appears to be preferred for general use at present because of its low resistance potential and superior pharmacokinetic profile (high and predictable serum peaks, wide toxic-therapeutic ratio, high "kill ratio," and q 12 h dosing). In spite of the introduction of the third generation cephalosporins, which are highly active against a variety of aerobic gram-negative organisms, the aminoglycosides will continue to play an important role in the treatment of gram-negative infections. Indeed, the expected usefulness of aminoglycosides may be prolonged by the introduction of the third generation cephalosporins since these drugs will probably be used in combination with aminoglycosides to extend spectrum and to take advantage of possible synergy.

First and second generation cephalosporins

Data on tissue levels of drugs are important, for they provide us with information on concentrations that can be achieved at the site of an infection. Yet many questions remain unanswered in this area such as whether it is better to achieve high levels in tissue rapidly as with bolus administration of a drug, or whether it is preferable to maintain levels of drug at lower but more prolonged levels, as with constant infusion administration of a drug. The goal in the future will be to correlate pharmacologic principles with the efficiency of various dosing programs and tissue levels in the clinical setting.

Ceforanide and cefazolin therapy of pneumonia: comparative clinical trial

Ceforanide is a new (parenteral) long-acting cephalosporin with antimicrobial activity comparable to those of other second-generation cephalosporins. In a randomized prospective study, patients with community-acquired bacterial pneumonia were treated with ceforanide at 0.5 g every 12 h (28 cases) or with cefazolin at 1.0 g every 8 h (26 cases). The study groups were comparable in clinical and laboratory findings, including etiological diagnosis. Streptococcus pneumoniae was isolated from the sputum of 38 patients, of whom 8 (21%) were bacteremic. Mean peak and trough serum levels of ceforanide drawn 1 and 11.5 h after the 0.5-g intravenous dose were 39.6 and 2.5 microgram/ml, respectively. Of the 50 patients evaluable for efficacy, all responded clinically with no serious adverse reactions. In spite of clinical improvement and in vitro susceptibility, Haemophilus influenzae persisted in the sputum of five of the eight cefazolin-treated patients and four of the five patients treated with ceforanide. Ceforanide appears to be as safe and effective as cefazolin for the therapy of pneumonia caused by S. pneumoniae or H. influenzae, but neither drug was effective in clearing H. influenzae from the sputum.

Anti-Pseudomonas activity in bronchial secretions of patients receiving amikacin or tobramycin as a continuous infusion

The penetration of amikacin and tobramycin into bronchial secretions and the resulting anti-Pseudomonas activity were assessed in two groups of tracheostomized or intubated patients with tracheobronchial infection and purulent bronchial secretions. The aminoglycosides were administered as continuous, high-dose intravenous infusions. The mean drug concentrations in serum and bronchial secretions were 12.8 and 2.0 microgram/ml for amikacin and 3.6 and 0.7 microgram/ml for tobramycin. The bronchial secretion/serum ratios varied over a wide range: from 9.6 to 22.8% (average, 14.9%) for amikacin and from 3 to 39.3% (average, 17.5%) for tobramycin. Sustained anti-Pseudomonas activities in bronchial secretions were achieved only in patients with very high aminoglycoside levels in serum. In most patients, however, no anti-Pseudomonas activity could be detected within bronchial secretions despite therapeutic levels of amikacin and tobramycin and adequate bactericidal activities in serum.

Therapeutic effects of cefotiam and cefazolin on experimental pneumonia caused by Klebsiella pneumoniae DT-S in mice

The efficacies of several dosage schedules, productive of plasma levels of cefotiam and cefazolin of short and long duration and starting at three levels of cefotiam and cefazolin of short and long duration and starting at three different times (3, 18, and 30h) after infection, were examined in experimental pneumonia caused by Klebsiella pneumoniae DT-S in mice. With each of the multiday regimens there was a large segment of the day when plasma levels fell below assayable concentrations. In all cases, cefotiam proved about eight times as active as cefazolin, indicating that the potent in vitro antibacterial activity of cefotiam was well reflected in the therapeutic effect in this model infection. As judged by the total dose administered, the regimen of cefotiam producing a low but sustained plasma level gave better therapeutic effects than that exhibiting a high but transient plasma level. The cefotiam levels in the plasma of mice that received the regimen effective when initiated at 18 h after infection were less than the expected levels in humans after intravenous infusion of the usual clinical dose.

Optimal antibiotic therapy in bronchopulmonary infections

Therapy of bronchopulmonary infections has evolved in the past 30 years. Only in the therapy of pneumococcal infections have, precise dosage programs been developed. Therapy of pneumococcal infection is optimal with penicillin G in low dosage. None of the newer agents has altered morbidity or mortality. The best agent for the treatment of pneumonia due to Staphylococcus aureus or members of the Enterobacteriaceae has not been established. Use of combination therapy consisting of an anti-Pseudomonas penicillin and an aminoglycoside has been shown to offer the greatest success in the treatment of Pseudomonas pulmonary infections. The optimal antibiotic and dosage program for the treatment of acute bacterial exacerbations of chronic bronchitis has yet to be defined. Further comparative studies of the chemotherapy of pulmonary infections are necessary.

Ceforanide (BL-S786) in the treatment of community-acquired bacterial pneumonia

Ceforanide (BL-S 786) is a new long-acting parenteral cephalosporin which has the major pharmacologic advantage of requiring only twice a day dosage. We treated 28 adult patients with community-acquired bacterial pneumonia using doses of 500 or 1000 mg every 12 hours. Twenty-four of 28 infections were due to Streptococcus pneumoniae and/or Hemophilus influenzae, and all pathogens were susceptible in vitro to both cephalothin and ceforanide. Patients were treated for a mean of 7.5 days, and all showed a good clinical and radiographic response with no mortality. Of the 13 patients with H. influenzae, the organism could still be recovered during therapy in 9/12 and post therapy in 3/8. One clinical superinfection (sepsis due to Pseudomonas aeruginosa) occurred during therapy. Side effects with therapy included thrombocytosis (15), asymptomatic eosinophilia (5), and mild elevation of the serum transaminases (3). These studies suggest that ceforanide is a safe and effective agent for the treatment of adult patients with bacterial pneumonia due to S. pneumoniae; further experience in therapy of H. influenzae is needed because of frequent failure of ceforanide to eradicate this organism from the sputum.

The concentration of tobramycin in bronchial secretions

Fifteen noninfected patients received three consecutive doses of tobramycin (1.7 mg/kg intramuscularly). Serum and bronchial secretions were obtained during bronchoscopy. Microbiologic assay demonstrated that bronchial secretions containing tobramycin produced inappropriately small zone sizes when compared with serum. Also, it was shown that bronchial secretions frequently do achieve therapeutic concentrations of tobramycin at this dosage level and route of administration.