Antibiotic penetration in abdominal infection: a case of tobramycin failure responsive to moxalactam

Behavior of antibiotics during human necrotizing pancreatitis

The aim of the study was to verify whether antibiotics excreted by the normal pancreas are also excreted in human necrotizing pancreatitis, reaching the tissue sites of the infection. Twelve patients suffering from acute necrotizing pancreatitis were treated with imipenem-cilastatin (0.5 g), mezlocillin (2 g), gentamicin (0.08 g), amikacin (0.5 g), pefloxacin (0.4 g), and metronidazole (0.5 g). Serum and necrotic samples were collected simultaneously at different time intervals after parenteral drug administration by computed tomography-guided needle aspiration, intraoperatively, and from surgical drainages placed during surgery. Drug concentrations were determined by microbiological and high-performance liquid chromatography assays. All antibiotics reached the necrotic tissues, but with varying degrees of penetration, this being low for aminoglycosides (13%) and high in the case of pefloxacin (89%) and metronidazole (99%). The concentrations of pefloxacin (13.0 to 23 micrograms/g) and metronidazole (8.4 micrograms/g) in the necrotic samples were distinctly higher than the MICs for the organisms most commonly isolated in this disease; the concentrations in tissue of imipenem (3.35 micrograms/g) and mezlocillin (8.0 and 15.0 micrograms/g) did not always exceed the MICs for 90% of strains tested, whereas the aminoglycoside concentrations in necrotic tissue (0.5 microgram/g) were inadequate. Repeated administration of drugs (for 3, 7, 17, and 20 days) seems to enhance penetration of pefloxacin, imipenem, and metronidazole into necrotic pancreatic tissue. The choice of antibiotics in preventing infected necrosis during necrotizing pancreatitis should be based on their antimicrobial activity, penetration rate, persistence, and therapeutic concentrations in the necrotic pancreatic area. These requisites are provided by pefloxacin and metronidazole and to a variable extent by imipenem and mezlocillin.

Mathematical examination of dual individualization principles (I): Relationships between AUC above MIC and area under the inhibitory curve for cefmenoxime, ciprofloxacin, and tobramycin

Traditional antibiotic dosage adjustments target predetermined serum concentrations, whereas a host of in vitro studies and recent clinical trials establish that bacteria vary in their susceptibility. Dual individualization, which considers the variance in both antibiotic pharmacokinetics and bacterial susceptibility, has been employed to describe different rates of bacterial eradication in relation to varying serum concentrations. In patients with nosocomial pneumonia, one of the model compounds studied was cefmenoxime, where a target six-hour area under the serum concentration-time curve (AUC) of 140 micrograms.h/mL above minimum inhibitory concentration (MIC) was previously associated with bacterial eradication in an average of four days. The target AUC value of 140 micrograms.h/mL above MIC is unique to cefmenoxime. Ideally, there should be a dual individualized target useful to adjust the dose of any antibiotic. Computer simulations performed to evaluate this hypothesis suggested that each antibiotic had a unique value for target AUC above MIC. These simulations indicated that an optimal AUC above MIC was about 80 percent of the total AUC above the MIC. Predictable rates of bacterial eradication would presumably result from maintaining these relationships across the range of bacterial susceptibility and the range of serum concentration profiles. Each antibiotic has a unique and different 24-hour AUC over MIC value associated with bacterial eradication in 4 days. For cefmenoxime, the target was 540 area units over MIC per 24 hours, tobramycin with 34 area units, and ciprofloxacin with 23 area units per 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefmenoxime efficacy, safety, and pharmacokinetics in critical care patients with nosocomial pneumonia

Nephrotoxicity frequently complicates the use of aminoglycosides in severely compromised acute care patients. Therefore, an open clinical trial was initiated to determine if cefmenoxime alone is useful in serious nosocomial pneumonias. Thirty consecutive patients were entered in the trial, and 28 patients with an average age of 66 years were evaluable. Most were malnourished at entry, with serum albumin averaging 2.8 g/dl and prognostic nutritional index values over 70 percent (normal less than 40 percent). One-half the patients had severe chronic obstructive pulmonary disease and 68 percent required ventilators. Fifty-seven percent had concomitant cardiac disease, and 79 percent had previously been treated with antibiotics. Pneumonia was proven to be present by new infiltrate on chest x-ray, new fever, elevated white blood cell count, and gram-negative rods on gram stain and in cultures of tracheal aspirates or sputum. Patients were given cefmenoxime 1 to 2 g every six hours an average of 12 days. Cefmenoxime peak (one hour) and trough concentrations were measured by high pressure liquid chromatography and averaged 58 and 7 micrograms ml, respectively. Pharmacokinetic data in 18 patients were determined from serum profiles. Gram-positive organisms, Escherichia coli, Klebsiella, and Hemophilus influenzae were usually eradicated. Persistence was noted for some Enterobacter, Pseudomonas, Serratia, and Acinetobacter. Persistence in patients with good clinical response was considered colonization rather than superinfection. Overall, a satisfactory clinical response rate was noted in 78.6 percent of evaluable patients, whereas four patients responded satisfactorily with recurrence and two treatments had an unsatisfactory response. No serious adverse effects were observed. Cefmenoxime is a promising agent in the treatment of susceptible pneumonias in critical care patients.

Moxalactam penetration into normal heart valve, cardiac vegetations, and myocardium in relation to protein binding and physiological distribution spaces

Rabbits with catheters implanted in the left ventricle were given a single dose of moxalactam and sacrificed at various times thereafter for measurement of the concentration of this antimicrobial agent in serum, heart muscle, and various heart valves. Penetration into both extravascular sites was rapid; steady state was achieved within 5 min after the dose. Moxalactam showed essentially complete penetration into valve lesions, whereas concentrations in heart muscle were only 20% of those in serum. The physiological distribution of moxalactam in heart muscle was beyond the inulin space, but substantially lower than total body water. This myocardial distribution ratio was not predicted by the serum-free fraction or blood trapped in tissues alone, but was in good agreement with that of extracellular fluid plus blood trapped in tissues. The moxalactam distribution profile was most compatible with that of drugs which are excluded from cells but readily distributed throughout extracellular fluids. This explains its nearly complete penetration into heart valves as well as its incomplete penetration into heart muscle, since the two sites differ in their relative proportions of cells and extracellular fluid spaces.