Pharmacokinetics of cefotaxime in patients after liver transplantation

Cefotaxime. A reappraisal of its antibacterial activity and pharmacokinetic properties, and a review of its therapeutic efficacy when administered twice daily for the treatment of mild to moderate infections

Cefotaxime is well established as an effective and well tolerated antibacterial drug for 3 times daily parenteral treatment of a variety of moderate to severe infections in hospitalised patients. Its frequency of administration has recently been reassessed with a 12-hourly regimen. Comparative studies in hospitalised patients with nosocomial or community-acquired lower respiratory tract infections, demonstrate the similar clinical and bacteriological efficacy of twice daily cefotaxime 1 or 2 g and the same daily dose of ceftriaxone, usually administered once daily. Cefotaxime 2 g twice daily was also similar in efficacy to ceftriaxone 2 g once daily. Retrospective and post-marketing studies also reveal the similar efficacy of cefotaxime administered twice and 3 times daily, and pharmacoeconomic studies suggest that total direct costs of treatment with cefotaxime compared is similar to that with other third generation cephalosporins in currently used dosage regimens. When administered twice daily, cefotaxime is, thus, an effective antibacterial agent for the treatment of hospitalised patients outside the intensive care unit with a variety of mild to moderate non-CNS infections caused by susceptible organisms. When appropriately administered twice daily there is potential to lower the cost of antibacterial treatment without compromising efficacy.

Anti-infective agents and hepatic disease

Numerous factors such as changes in plasma protein binding, tissue binding, hepatic blood flow, hepatic metabolism, and distribution may occur in hepatic disease. The impact of these physiologic changes on pharmacokinetic and pharmacodynamic parameters of anti-infective agents is likely to be clinically significant. Unfortunately, these issues have not been thoroughly investigated. Even within the same type of liver disease, there is considerable interpatient variability in pharmacokinetic variables, rendering it difficult to predict drug disposition accurately. Pharmacokinetics of selected anti-infective agents are altered in hepatic disease, necessitating careful monitoring and dosage titration to avoid enhanced drug concentrations and risk of toxicity.

Plasma levels of piperacillin and vancomycin used as prophylaxis in liver transplant patients

The pharmacokinetics of piperacillin and vancomycin used intravenously as antibioprophylaxis were measured in the plasma and bile during orthotopic liver transplantation. Piperacillin (4 g and then 2 g every 4 h) and vancomycin (1 g and then 0.5 g every 6 h) were infused in 10 patients. During vascular clamping without venovenous bypass, clearance of both antibiotics decreased in relation to renal insufficiency. During the surgical procedure, volume of distribution of both drugs increased because of fluid redistribution. The peaks of piperacillin after first, second and third administrations were respectively 314, 265 and 210 mg.l-1, while trough levels were 46.5, 55.2 and 54.5 mg.l-1. The peaks of vancomycin were 54.4, 49.6 and 40.9 mg.l-1, while first and second trough levels were 9.5 and 12 mg.l-1. These plasma concentrations were quite similar to levels reported in healthy subjects despite large blood loss and fluid replacement. However, piperacillin trough concentrations (< 64 mg/l) were too low in relation to its concentration-dependent antibacterial activity and vancomycin peak concentrations (> or = 40 mg/l) were slightly too high in relation to its toxicity.

Beta-Lactam antibiotic-induced leukopenia in severe hepatic dysfunction: risk factors and implications for dosing in patients with liver disease

PURPOSE

To determine if an association could be established for leukopenia and administration of beta-lactam antibiotic therapy in patients with hepatic dysfunction. If such an association could be found, to determine the incidence, timing, and risk factors for beta-lactam antibiotic-induced leukopenia.

PATIENTS AND METHODS

Patients with hepatic dysfunction, i.e., liver transplant recipients as well as patients with end-stage liver disease awaiting liver transplantation, seen at our institution between October 1989 and October 1991, who received 7 or more days of antibiotics, were studied in a prospective observational fashion. Complete blood count was determined at baseline and followed until the completion of the antibiotic course or until the resolution of leukopenia in leukopenic patients.

RESULTS

Leukopenia occurred after a mean of 6 days with 23% of the beta-lactam antibiotic courses as compared with 0% with the non-beta-lactam antibiotic courses (p = 0.046). Development of leukopenia correlated with the severity of liver disease. Patients developing leukopenia had worse synthetic hepatic function as evidenced by a lower serum albumin level (p < 0.01), a lower serum cholesterol level (p < 0.05), and a higher prothrombin time (p < 0.01) as compared with the patients without leukopenia. Leukopenic patients had a lower baseline white blood cell count (p < 0.051) and a lower baseline platelet count (p < 0.01) indicative of a greater degree of hypersplenism. Leukopenic patients received a higher mean daily dosage of cephalosporins as compared with nonleukopenic patients.

CONCLUSION

beta-Lactam antibiotics when administered in usually recommended dosages can induce leukopenia in patients with hepatic dysfunction. The probable mechanism is impaired hepatic metabolism of the beta-lactam antibiotics resulting in bone marrow suppression of white cell precursors from excessive antibiotic concentrations. The more severe the hepatic dysfunction, the greater the risk. We propose a reduction in dosages of beta-lactam antibiotics when used in patients with hepatic dysfunction. Finally, we raise the possibility that this adverse drug effect is more common than currently recognized by physicians.