Tranexamic acid through intravenous,intramuscular and oral routes: an individual participant data meta‐analysis of pharmacokinetic studies in healthy volunteers

Tranexamic acid (TXA) is an antifibrinolytic drug that reduces surgical blood loss and death due to bleeding after trauma and post‐partum haemorrhage. One key issue for treatment success is early administration. While usually given intravenously, oral and intramuscular use would be useful in specific circumstances. Therefore, an understanding of TXA pharmacokinetics when given via different routes is valuable. The aim of this study was to perform an individual participant data meta‐analysis of pharmacokinetic studies with TXA given to healthy volunteers via different routes. We searched the following databases: PubMed, Web of Science, Wiley Online Library, Elsevier Science Direct and J‐STAGE. Individual subject data were extracted when available, otherwise arithmetic means were used. A population pharmacokinetic model was developed using nonlinear mixed effect modelling. Seven studies were included in the analysis with data from 10 patients for the IV route, six patients for the IM route and 114 patients for the oral route. The pharmacokinetics was ascribed to a two‐compartment model, and the main covariate was allometrically scaled bodyweight. Oral and IM bioavailabilities were 46 and 105%, respectively. For a 70 kg bodyweight, the population estimates were 7.6 L/h for clearance, 17.9 L for the volume of the central compartment, 2.5 L/h for the diffusional clearance and 16.6 L for the peripheral volume of distribution. Larger well‐designed studies are needed to describe the pharmacokinetics of TXA when given IM or as an oral solution before these can be recommended as alternatives to IV.     

Variation in serum binding of tertatolol mediated by disease-induced modification of alpha-acid glycoprotein concentration

Summary The serum concentrations of ₁-acid glycoprotein (AAG), albumin (HSA) and non-esterified fatty acids, and the serum binding of tertatolol were measured in four groups of individuals: healthy control subjects (n=24), and patients with inflammation (n=28), and hepatic (n=20) and renal (n=27) insufficiency.Serum binding of tertatolol was increased in patients with inflammation (94.6%), decreased in patients with hepatic insufficiency (88.8%) and it was unchanged in patients with renal insufficiency (92.8%) as compared to controls (92.7%).Multivariate analysis indicated that the changes were mainly related to concomitant changes in AAG concentration, which could account for 57% of intersubject variability in the bound/free ratio, and to a lesser extent in HSA, which accounted for only 4% of the variability in the binding.The data show that the free fraction of the basic drug tertatolol in serum is affected by pathological conditions that cause changes in AAG concentration.     

Ciliated protozoa in the colonic wall of horses

Ciliated protozoa of several morphological types were found in the colonic tissue of 8 horses, mostly immature Standardbreds. Most of the protozoa observed appeared similar to those normally found as commensals in the equine large intestinal lumen. In all cases, organisms were located in the lamina propria; organisms were also found in the submucosa of 2 horses. The association of colonic disease with the presence of intramural ciliates was unclear.     

A limited-sampling method for evaluation of the area under the curve of ultrafilterable carboplatin in children

Carboplatin is a widely used cytotoxic agent in numerous solid tumors of children. Since there is a large degree of interpatient variability in the area under the curve of free carboplatin for a given dose of the drug, the current tendency is to adjust the carboplatin dose so as to reach a target area under the curve rather than to determine a carboplatin dose on the basis of the body surface area. A limited-sampling method was developed for estimation of the ultrafilterable carboplatin area under the curve and for adjustment of the carboplatin dose on subsequent treatments. Population parameters were obtained from 16 children (reference group). We used the maximum a posteriori (MAP) Bayesian approach on 15 children with complete carboplatin pharmacokinetic data (test group). Two blood samples were sufficient to obtain reliable prediction of the area under the curve. The best sampling times were: (a) 30 min after the end of the infusion and (b) 5 h after the end of the infusion. On the basis of these data it is possible to prescribe prospectively a target area under the curve for free carboplatin given in a fractionated daily infusion and to adapt the carboplatin dose directly to ultrafilterable carboplatin measurements. Received: 8 June 1997 / Accepted: 9 January 1998     

Effect of recombinant interleukin-2 pretreatment on oral and intravenous digoxin pharmacokinetics and P-glycoprotein activity in mice.

P-glycoprotein (P-gp) is an ATP-dependent efflux membrane transporter involved in many drug pharmacokinetics in humans. Decreasing its expression could enhance the bioavailability of substrates as digoxin. We have recently found that human recombinant interleukin-2 (rIL2) in vivo decreases P-gp expression in intestine and brain of mice and modifies oral digoxin pharmacokinetics. The aim of the study was to evaluate the involvement of bioavailability in the rIL2 pretreatment effect on digoxin pharmacokinetics by comparing oral and i.v. digoxin pharmacokinetics before and after rIL2 pretreatment (10 microg/kg). We also tried to show the possible effect of a low rIL2 dose (1 microg/kg) pretreatment on oral digoxin pharmacokinetics. First, adult Swiss mice received a single oral or i.v. dose of digoxin (0.03 mg/kg). Two weeks later, the same animals were treated by rIL2 i.p. twice a day (10 microg/kg) for 4 days and received digoxin again at day 5. As well, another group received oral digoxin (0.03 mg/kg) with a 1 microg/kg rIL2 pretreatment. Blood was collected after digoxin administration with and without rIL2 pretreatment. Digoxin pharmacokinetics were described by a one-compartment model. The 10 microg/kg rIL2 pretreatment did not modify i.v. digoxin pharmacokinetics, whereas oral digoxin pharmacokinetics were significantly modified by the 10 microg/kg rIL2 pretreatment and not by the 1 microg/kg rIL2 pretreatment. The decrease of P-gp activity, caused by rIL2 (10 microg/kg), increased digoxin bioavailability. An increase in exposure and intracellular level of drugs is expected from rIL2 pretreatment.     

Recombinant interleukin-2 treatment decreases P-glycoprotein activity and paclitaxel metabolism in mice

Recombinant rIL-2 was reported to be able to decrease P-glycoprotein (P-gp) expression in cultured cells from human colon carcinoma. P-gp is considered an important factor in the control of Taxol efflux from tumor cells. Based on the premise that Taxol pharmacokinetic parameters could be modified as a result of diminished P-gp expression induced by recombinant interleukin (rIL)-2 and that this might elicit an interaction between the two drugs, we evaluated the pharmacokinetics of a novel strategy combining i.p. immunotherapy with rIL-2 and a cytotoxic agent, Taxol. Mice were allocated to two groups treated with rIL-2 (15 microg x 2/day from day 1 to 4) then Taxol (10 mg/kg i.p. day 5) or Taxol (10 mg/kg i.p.) alone (control group). The Taxol + rIL-2 combination provoked the development of ascites, presumably due to the presence of Cremophor EL in the Taxol preparation. Paclitaxel was measured in plasma and ascites by HPLC with UV detection. Paclitaxel pharmacokinetics were strongly modified by rIL-2 pretreatment. Compared to that observed in control mice, the apparent volume of distribution increased dramatically (Vd/F = 18.2 versus 4.1 l/kg) and the apparent plasma clearance decreased (Cl/F = 1.12 versus 1.66 l/h/kg). P-gp expression was determined in the liver, lung, intestine, brain and kidney in the two groups by immunodetection with the C219 anti-P-gp monoclonal antibody. A significant decrease in P-gp expression was observed in the intestine and in the brain in the rIL-2-pretreated mice as compared to controls. To study the functionality of P-gp, we compared digoxin (a model P-gp substrate) pharmacokinetics before and after pretreatment with rIL-2 (10 microg x 2/day from day 1 to 4), after a single 1 microg oral dose of digoxin used to quantify P-gp activity. Results showed a decrease in oral digoxin clearance after rIL-2 pretreatment indicating modified P-gp activity. We conclude that rIL-2 pretreatment is able to decrease P-gp activity and paclitaxel metabolism in vivo. This is the first study to demonstrate a decrease in P-gp activity and expression in organs such as the brain in vivo. A novel strategy combining immunotherapy with rIL-2 and a cytotoxic agent could potentially improve clinical results, particularly in brain cancer.     

Neurosyphilis in newly admitted psychiatric patients: three case reports

BACKGROUND: Neurosyphilis, also known as "general paresis of the insane," at one time accounted for a large portion of admissions to state psychiatric facilities. With the introduction of antibiotics, neurosyphilis is now considered very rare. METHOD: Chart review was performed on patients diagnosed with neurosyphilis who were admitted to a state psychiatric hospital in Raleigh, N.C., during 2002. RESULTS: We identified 3 cases of confirmed neurosyphilis, representing 0.1% of adult admissions, diagnosed in newly admitted psychiatric patients. None of the patients were immunocompromised. Response to antibiotic treatment was poor. CONCLUSIONS: Given the increase in primary and secondary syphilis reported in the 1980s and early 1990s, routine screening of psychiatric patients for the presence of syphilis should be considered.     

Modelling of ftorafur and 5-fluorouracil pharmacokinetics following oral UFT administration. A population study in 30 patients with advanced breast cancer

PURPOSE: The pharmacokinetics of ftorafur, 5-fluorouracil (5FU) and uracil were investigated in order to built a population pharmacokinetic model for the anticancer drug UFT, administered with leucovorin and vinorelbine. METHODS: A total of 31 patients with metastatic breast cancer were treated with escalating oral doses of UFT (300 to 500 mg per day) plus leucovorin (90 mg per day) in combination with intravenous vinorelbine (15 to 25 mg/m(2)). Concentration-time data were obtained on days 1, 8, 15 and 21 of cycle 1. RESULTS: Of the 31 patients treated, 30 were available for the pharmacokinetic analysis. Ftorafur, 5FU and uracil appeared rapidly in plasma and showed large interpatient variations. Ftorafur concentrations were higher than those of 5FU and uracil. AUC significantly increased between day 1, and days 8, 15 and 21. Ftorafur C(max) and AUC values were proportional to UFT dose, whereas C(max) and AUC values of 5FU and uracil were not linearly related to UFT dose. The pharmacokinetics of ftorafur were ascribed to a two-compartment open model in which 5FU was produced from the central compartment. The absorption and exponential distribution rate constants were assumed equal. The effect of uracil on 5FU elimination was straightforward, since no reasonable curve-fitting could be obtained for 5FU data when this covariate was not taken into account. The uracil concentration inducing a 50% reduction in 5FU elimination was 2.67 micro mol.l(-1). This result confirms the important role played by uracil as a competitive inhibitor of 5FU catabolism. CONCLUSION: A pharmacokinetic model for ftorafur and 5FU was developed and should be useful to further study drug interactions and establish dosing guidelines.     

In Vitro Binding and Partitioning of Irinotecan (CPT-11) and its Metabolite, SN-38, in Human Blood

The binding of CPT-11 and SN-38 to human plasma proteinswas studied by ultrafiltration at 37°C and pH 7.4. In plasma,CPT-11 was 66–60% bound in the range 100–4000ng/ml and SN-38 was 94–96% bound in the range50–200 ng/ml. At these concentrations the plasma bindingof CPT-11 was slightly saturable, but the plasma binding of SN-38was concentration-independent. Albumin was the main carrier ofCPT-11 and SN-38 in plasma. In blood, the binding of CPT-11 wasmoderate (80%), mainly to plasma proteins (47%) anderythrocytes (33%). The binding of SN-38 was high(99%) and most of SN-38 in blood was located in bloodcells (approximately 66%) The simulation of a grade 3hematotoxicity (according to National Cancer Institute's CommonToxicity Criteria grading) on the SN-38 blood distributionyielded an increase in fu (free fraction of drug in plasma) from1.05 to 2.08 and a decrease in C_Bl/C_P from1.66 to 1.14 (both resulting from a decreased cellbinding).