Therapeutic Doses of Eltrombopag do not Inhibit Hepatic BCRP in Healthy Volunteers: Intravenous Ceftriaxone as a Model.

PURPOSE: Ceftriaxone elimination occurs through breast cancer resistance transporter (BCRP) and multidrug resistance-associated protein 2 (MRP-2) which are expressed on the canalicular membrane of hepatocytes. Eltrombopag, a thrombopoetin receptor agonist used in the treatment of immune thrombocytopenic purpura, is reported in in vitro studies as an inhibitor of intestinal BCRP but not an inhibitor of hepatic BCRP. Thus, the present study evaluates the effect of therapeutic doses of eltrombopag on the clinical pharmacokinetics of intravenous ceftriaxone. METHODS: Healthy adult (n=12) were treated with oral doses of eltrombopag (0, 25 or 50 mg) 28 and 4 h prior to intravenous ceftriaxone administration (1g). Serial blood samples were collected up to 48 h after ceftriaxone administration and plasma samples were analysed by LC-MS/MS using 50 µL aliquots (total concentration) and 100 µL (unbound concentration). RESULTS: A method to analyze total and unbound ceftriaxone in plasma using LC-MS/MS was developed and validated with linearity from 1 to 200 µg/mL. Both methods are sensitive, precise and accurate with coefficients of variation less than 15% in the study of inter- and intra-assay precision and accuracy. Ceftriaxone pharmacokinetics in healthy adults were described using a bicompartmental model, with a mean clearance of 0.96 L/h (CI95% 0.71-1.20) and AUC0-∞of 1106 mg.h/mL (CI95% 811-1400) for volunteers that received only ceftriaxone; clearance of 0.95 L/h (CI95% 0.77-1.13) and AUC0-∞ of 1083 mg.h/mL (CI95% 876-1290) for volunteers that received ceftriaxone plus 25 mg of eltrombopag and clearance of 0.96 L/h (CI95% 0.74-1.19) and AUC0-∞ of 1072 mg.h/mL (CI95% 872-1273) for volunteers that received ceftriaxone plus 50 mg of eltrombopag. CONCLUSIONS: The results do not support the existence of a clinical pharmacokinetic drug interaction involving hepatic BCRP in human subjects receiving intravenous ceftriaxone and oral eltrombopag. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Pharmacokinetics of ceftriaxone after intravenous, intramuscular and subcutaneous administration to domestic cats.

The pharmacokinetic properties of ceftriaxone, a third-generation cephalosporin, were investigated in five cats after single intravenous, intramuscular and subcutaneous administration at a dosage of 25 mg/kg. Ceftriaxone MICs for some gram-negative and positive strains isolated from clinical cases were determined. Efficacy predictor (t > MIC) was calculated. Serum ceftriaxone disposition was best fitted by a bicompartmental and a monocompartmental open models with first-order elimination after intravenous and intramuscular and subcutaneous dosing, respectively. After intravenous administration, distribution was fast (t1/2d 0.14 +/- 0.02 h) and moderate as reflected by the volume of distribution (V(d(ss))) of 0.57 +/- 0.22 L/kg. Furthermore, elimination was rapid with a plasma clearance of 0.37 +/- 0.13 L/h.kg and a t1/2 of 1.73 +/- 0.23 h. Peak serum concentration (Cmax), tmax and bioavailability for the intramuscular administration were 54.40 +/- 12.92 microg/mL, 0.33 +/- 0.07 h and 85.72 +/- 14.74%, respectively; and for the subcutaneous route the same parameters were 42.35 +/- 17.62 microg/mL, 1.27 +/- 0.95 h and 118.28 +/- 39.17%. Ceftriaxone MIC for gram-negative bacteria ranged from 0.0039 to >8 microg/mL and for gram-positive bacteria from 0.5 to 4 microg/mL. t > MIC was in the range 83.31-91.66% (10-12 h) of the recommended dosing interval (12 h) for Escherichia coli (MIC90 = 0.2 microg/mL).

Pharmacokinetics of ceftriaxone administered by the intravenous, intramuscular or subcutaneous routes to dogs.

The purpose of this study was to investigate the pharmacokinetics of ceftriaxone after single intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) doses in healthy dogs. Six mongrel dogs received ceftriaxone (50 mg/kg) by each route in a three-way crossover design. Blood samples were collected in predetermined times after drug administration. Results are reported as mean +/- standard deviation (SD). Total body clearance (Cl(t)) and apparent volume of distribution (V(z)) for the i.v. route were 3.61 +/- 0.78 and 0.217 +/- 0.03 mL/kg, respectively. Terminal half-life harmonic mean (t(1/2 lambda)) was 0.88; 1.17 and 01.73 h for the i.v., i.m and s.c. routes, respectively. Mean peak serum concentration (C(max)) was 115.10 +/- 16.96 and 69.28 +/- 14.55 microg/mL for the i.m and s.c. routes, respectively. Time to reach C(max) (t(max)) was 0.54 +/- 0.24 and 1.29 +/- 00.64 h for the i.m and s.c. routes, respectively. Mean absorption time (MAT) was 1.02 +/- 0.64 and 2.23 +/- 00.73 h for the i.m and s.c. routes, respectively. Bioavailability was 102 +/- 27 and 106 +/- 14% for the i.m and s.c. routes, respectively. Statistically significant differences were determined in C(max), t(max), MAT and t(1/2 lambda) of s.c. administered ceftriaxone when compared with the i.v and i.m. routes. These findings suggest that once or twice s.c. or i.m. daily administered ceftriaxone should be adequate to treat most susceptible infections in dogs.

Ceftriaxone is an efficient component of antimicrobial regimens in the prevention and initial management of infections in end-stage renal disease.

BACKGROUND: Infection is a frequent complication in patients with end-stage renal disease. The most common organisms isolated are gram-positive cocci and gram-negative bacilli. Therefore, the usual initial therapeutic approach in these situations is the simultaneous intravenous administration of vancomycin plus an aminoglycoside. This treatment's adverse effects include ototoxicity, nephrotoxicity, and less than ideal tissue penetrance. METHODS: We assessed the efficacy of intravenous ceftriaxone in the prevention and in the initial empirical treatment of infections in end-stage renal disease patients, and tested the stability of blood levels of this antibiotic in this population. We studied 104 patients, 65 of them falling into the prevention group (1 g of ceftriaxone i.v. for 5 days) and 39 into the treatment group (1 g of ceftriaxone i.v. or intraperitoneally for 10-14 days). RESULTS: Peak serum ceftriaxone concentrations were well above the minimal inhibitory concentration for 90% of strains. Trough serum concentrations of the drug prior to the next dose were also considerably in excess of the minimal inhibitory concentration. In the prevention group, 8 of 65 developed an infection, which was sensitive to ceftriaxone, whereas in 22 of the 39 patients from the treatment group, cultures showed organisms sensitive to ceftriaxone and in the remaining 17 patients sensitivity was not done. CONCLUSIONS: The present study demonstrates the efficacy of a simplified dosing schedule in achieving blood levels of the antibiotic well in excess of minimal inhibitory concentration of any of the organisms encountered. It also shows the usefulness of ceftriaxone in the prevention and/or treatment of bacterial infections and the lack of the side effects vancomycin and/or aminoglycosides possess.

Intrapartum prophylaxis with ceftriaxone decreases rates of bacterial colonization and early-onset infection in newborns.

Because of high rates of neonatal gram-negative sepsis in many Latin American countries, we prospectively enrolled 784 high-risk pregnant women in a study designed to evaluate the effect of a single 1-g dose of ceftriaxone (n = 390) vs. that of no antibiotic prophylaxis (n = 394) on oral, rectal, and umbilical colonization and fatality rates among newborn infants. The mean ceftriaxone concentration in cord blood samples was 26 microgram/mL (range, 9-40 microgram/mL). Compared with infants of untreated mothers, children born to women who were given ceftriaxone were colonized at a lesser rate by gram-negative bacilli (54% vs. 35%; P < .001) and by group B streptococci (54% vs. 21%; P = .03) and endured significantly fewer sepsis-like illnesses in the first 5 days of life (8.1% vs. 3.1%; P = .004). There was also a tendency for them to have fewer episodes of culture-proven early-onset sepsis (2.8% vs. 0.5%; P = .06). Sepsis-related case-fatality rates (0.8% and 0.3%, respectively) were not significantly different. Although intrapartum administration of a single dose of ceftriaxone to high-risk mothers could be a safe and potentially useful strategy for reducing early-onset neonatal infections, additional information is required before this approach can be recommended for routine prophylaxis.

Single-dose pharmacokinetics of ceftriaxone in patients with end-stage renal disease and hemodialysis.

We report the pharmacokinetic parameters of ceftriaxone in 11 patients on hemodialysis with end-stage renal disease (ESRD; creatinine clearance less than 5 ml/min/1.73 m2). The patients were studied during the interdialysis period and during 4 h of hemodialysis. The mean age was 53.4 years. After the administration of 1 g of ceftriaxone during a constant intravenous infusion over a 30-min period, t 1/2 was 16.6 h, beta was 0.0418 +/- 0.0106 h-1, VD was 14.5 +/- 3.0 liters/1.73 m2 and Clp was 0.40 +/- 0.05 liters/h for the interdialysis period. Hemodialysis started 24 h after the infusion. The initial plasma ceftriaxone concentration was 68.6 +/- 10.8 micrograms/ml. This value dropped to 40.4 +/- 4.7 micrograms/ml at the end of the 4th hour, indicating a significant 41% decay in blood levels during hemodialysis (p less than 0.001). The t 1/2 decreased to 4.88 h, kel rose to 0.142 +/- 0.0250 h-1 and Clp increased to 1.73 +/- 0.44 liters/h. All values were highly significantly different (p less than 0.001) from those during the interdialysis period. The plasma ceftriaxone concentration of 40.4 +/- 4.7 micrograms/ml at the end of hemodialysis was well within the therapeutic range of the drug. We conclude that ceftriaxone has a moderated increase in t 1/2 in patients with ESRD. Ceftriaxone is significantly dialyzable, however, the plasma concentrations are in the therapeutic range by the end of a 4-hour hemodialysis, 28 h after the administration of the drug. We propose that 1 g given intravenously before each hemodialysis will be sufficient to keep the patient's plasma concentrations within the therapeutic range until the next hemodialysis.(ABSTRACT TRUNCATED AT 250 WORDS)