Intestinal and hepatic contributions to the pharmacokinetic interaction between gamithromycin and rifampicin after single-dose and multiple-dose administration in healthy foals.

BACKGROUND: Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative. OBJECTIVES: To evaluate the pharmacokinetic interactions and pulmonary distribution of rifampicin and gamithromycin in healthy foals, and to investigate the cellular uptake of gamithromycin in vitro. STUDY DESIGN: Controlled, four-period, consecutive, single-dose and multiple-dose study. METHODS: Pharmacokinetics and lung distribution of rifampicin (10 mg/kg) and gamithromycin (6 mg/kg) were measured in nine healthy foals using LC-MS/MS. Enzyme induction was confirmed using the 4ß-OH-cholesterol/cholesterol ratio. Affinity of gamithromycin to drug transport proteins was evaluated in vitro using equine hepatocytes and MDCKII-cells stably transfected with human OATP1B1, OATP1B3 and OATP2B1. RESULTS: Rifampicin significantly (P<0.05) increased the plasma exposure of gamithromycin (16.2 ± 4.77 vs. 8.57 ± 3.10 µg × h/mL) by decreasing the total body clearance. Otherwise, gamithromycin significantly lowered plasma exposure of single- and multiple-dose rifampicin (83.8 ± 35.3 and 112 ± 43.1 vs. 164 ± 96.7 µg × h/mL) without a change in metabolic ratio and half-life. Gamithromycin was identified as an inhibitor of human OATP1B1, OATP1B3 and OATP2B1 and as a substrate of OATP2B1. In addition, it was extracted by equine hepatocytes via a mechanism which could be inhibited by rifampicin. MAIN LIMITATIONS: Influence of gamithromycin on pulmonary distribution of rifampicin was not evaluated. CONCLUSION: The plasma exposure of gamithromycin is significantly increased by co-administration of rifampicin which is most likely caused by inhibition of hepatic elimination.

Pharmacokinetics and pulmonary distribution of gamithromycin after intravenous administration in foals.

The long-acting azalide antibiotic gamithromycin is marketed for intramuscular treatment of bovine and swine infections. Off-label use in foals leads to severe local lesions likely caused by hyperosmolality of the injected solution. We provide evidence from a pharmacokinetic study in 10 warm-blooded healthy foals for intravenous bolus injection of gamithromycin diluted in distilled water to be a safe and well tolerated alternative. By intravenous dosing, markedly higher plasma exposure and better penetration into bronchoalveolar lavage cells but lower distribution into epithelial lining fluid are achieved as after intramuscular or subcutaneous administration. Intravenously injected gamithromycin was tolerated without any adverse drug reactions. The protocols for treatment of equine pulmonary infections caused by Rhodococcus equi should be revised accordingly.

Pharmacological indices and pulmonary distribution of rifampicin after repeated oral administration in healthy foals.

BACKGROUND: The treatment of equine lung infections by Rhodococcus equi with rifampicin is empirically based because pharmacokinetic/pharmacodynamic (PK/PD) indices and pivotal clinical outcome data are not available. OBJECTIVES: To evaluate the pharmacokinetics and pulmonary distribution of rifampicin into epithelial lining fluid (ELF) and bronchoalveolar lavage cells (BALC) to predict antimicrobial activity in the lung using PK/PD indices. STUDY DESIGN: Controlled, randomised, two-period, crossover, repeated-dose study with an initial arm to measure disposition after i.v. administration of rifampicin. METHODS: Pharmacokinetics and lung distribution were evaluated in six healthy foals treated with 10 mg/kg bwt rifampicin i.v. (initial arm) and with repeated oral doses of rifampicin at 10 mg/kg bwt and 20 mg/kg bwt once per day for 10 days (crossover arms). ELF and BALC were sampled by bronchoalveolar lavage 24 h after the last oral dosing. Rifampicin and 25-O-desacetyl rifampicin were quantified using liquid chromatography tandem-mass spectrometry. Enzyme induction by rifampicin was confirmed by evaluation of plasma 4ß-OH-cholesterol:cholesterol ratios. RESULTS: The distribution volume of rifampicin administered i.v. was ~0.85 L/kg. Terminal elimination half-life was ~11 h. Orally given rifampicin was slowly absorbed (Tmax , range: 2.5-8.0 h) and eliminated with apparent half-lives of ~6-8 h. Trough concentrations in ELF and BALC were 1.01 ± 0.20 µg/mL and 1.25 ± 0.29 µg/mL, respectively, after 10 mg/kg bwt rifampicin and 2.71 ± 1.25 µg/mL and 3.09 ± 1.63 µg/mL, respectively, after 20 mg/kg bwt rifampicin. The average ratios of area under the plasma concentration time curve during an administration interval of 24 h (AUC0-24 h ) to minimum inhibitory concentration (MIC) were 145 and 322 h, respectively, for less susceptible strains of R. equi (MIC90 : 0.5 µg/mL). MAIN LIMITATIONS: The clearance and bioavailability of rifampicin after repeated oral dosing were not evaluated. CONCLUSIONS: Treatment with rifampicin at 10 mg/kg bwt administered once per day is suitable to generate drug concentrations above the MIC90 in the ELF and BALC of foals. Future clinical studies with rifampicin in combination with macrolide antibiotics with low drug interaction potential are required to translate the PK/PD indices into protocols for the treatment of R. equi lung infections.

Phase I study of safety and pharmacokinetics of the anti-MUC16 antibody-drug conjugate DMUC5754A in patients with platinum-resistant ovarian cancer or unresectable pancreatic cancer.

BACKGROUND: MUC16 is a tumor-specific antigen overexpressed in ovarian (OC) and pancreatic (PC) cancers. The antibody-drug conjugate (ADC), DMUC5754A, contains the humanized anti-MUC16 monoclonal antibody conjugated to the microtubule-disrupting agent, monomethyl auristatin E (MMAE). PATIENTS AND METHODS: This phase I study evaluated safety, pharmacokinetics (PK), and pharmacodynamics of DMUC5754A given every 3 weeks (Q3W, 0.3-3.2 mg/kg) or weekly (Q1W, 0.8-1.6 mg/kg) to patients with advanced recurrent platinum-resistant OC or unresectable PC. Biomarker studies were also undertaken. RESULTS: Patients (66 OC, 11 PC) were treated with DMUC5754A (54 Q3W, 23 Q1W). Common related adverse events (AEs) in >20% of patients (all grades) over all dose levels were fatigue, peripheral neuropathy, nausea, decreased appetite, vomiting, diarrhea, alopecia, and pyrexia in Q3W patents, and nausea, vomiting, anemia, fatigue, neutropenia, alopecia, decreased appetite, diarrhea, and hypomagnesemia in Q1W patients. Grade ≥3-related AE in ≥5% of patients included neutropenia (9%) and fatigue (7%) in Q3W patients, and neutropenia (17%), diarrhea (9%), and hyponatremia (9%) in Q1W patients. Plasma antibody-conjugated MMAE (acMMAE) and serum total antibody exhibited non-linear PK across tested doses. Minimal accumulation of acMMAE, total antibody, or unconjugated MMAE was observed. Confirmed responses (1 CR, 6 PRs) occurred in OC patients whose tumors were MUC16-positive by IHC (2+ or 3+). Two OC patients had unconfirmed PRs; six OC patients had stable disease lasting >6 months. For CA125, a cut-off of ≥70% reduction was more suitable for monitoring treatment response due to the binding and clearance of serum CA125 by MUC16 ADC. We identified circulating HE4 as a potential novel surrogate biomarker for monitoring treatment response of MUC16 ADC and other anti-MUC16 therapies in OC. CONCLUSIONS: DMUC5754A has an acceptable safety profile and evidence of anti-tumor activity in patients with MUC16-expressing tumors. Objective responses were only observed in MUC16-high patients, although prospective validation is required. CLINICAL TRIAL NUMBER: NCT01335958.

Single locus sex determination and female heterogamety in the basket willow (Salix viminalis L.).

Most eukaryotes reproduce sexually and a wealth of different sex determination mechanisms have evolved in this lineage. Dioecy or separate sexes are rare among flowering plants but have repeatedly evolved from hermaphroditic ancestors possibly involving male or female sterility mutations. Willows (Salix spp.) and poplars (Populus spp.) are predominantly dioecious and are members of the Salicaceae family. All studied poplars have sex determination loci on chromosome XIX, however, the position differs among species and both male and female heterogametic system exists. In contrast to the situation in poplars, knowledge of sex determination mechanisms in willows is sparse. In the present study, we have for the first time positioned the sex determination locus on chromosome XV in S. viminalis using quantitative trait locus mapping. All female offspring carried a maternally inherited haplotype, suggesting a system of female heterogamety or ZW. We used a comparative mapping approach and compared the positions of the markers between the S. viminalis linkage map and the physical maps of S. purpurea, S. suchowensis and P. trichocarpa. As we found no evidence for chromosomal rearrangements between chromosome XV and XIX between S. viminalis and P. trichocarpa, it shows that the sex determination loci in the willow and the poplar most likely do not share a common origin and has thus evolved separately. This demonstrates that sex determination mechanisms in the Salicaceae family have a high turnover rate and as such it is excellent for studies of evolutionary processes involved in sex chromosome turnover.

Percutaneous cholecystostomy in critically ill patients with acute cholecystitis: complications and late outcome.

AIM: To evaluate the outcome of percutaneous cholecystostomy in critically ill patients with acute cholecystitis. MATERIALS AND METHODS: The study group included critically ill patients who underwent percutaneous cholecystostomy for acute cholecystitis at a tertiary medical centre in 2007-2011. Data on complications, morbidities, surgical outcome, and imaging findings were collected from the medical files and radiology information system. RESULTS: There were 48 women (59.3%) and 33 men (40.7%), with a median age of 82 years (range 47-99 years). Seventy-one (88%) had calculous cholecystitis and 10 (12%), acalculous cholecystitis. The drain was successfully inserted in all cases with no immediate major procedural complications. Fifteen patients (18.5%) died in-hospital within 30 days, mainly (93%) due to septic shock (14/15), another 20 patients (24.7%) died during the study period of unrelated co-morbidities. Of the remaining 46 patients, 36 (78.2%) had surgical cholecystectomies. In patients with acalculous cholecystitis, the drain was removed after cessation of symptoms. Transcystic cholangiography identified five patients with additional stones in the common bile duct. They were managed by pushing the stones into the duodenum via the cystostomy access, sparing them the need for surgical exploration. CONCLUSIONS: Early percutaneous gallbladder drainage is safe and effective in critically ill patients in the acute phase of cholecystitis, with a high technical success rate. Surgical results in survivors are better than reported in patients treated surgically without drainage. Bile duct stones can be eliminated without creating an additional access.

Low mitochondrial variability in birds may indicate Hill-Robertson effects on the W chromosome.

Interference among loci subject to selection (the Hill-Robertson effect) may considerably reduce levels of adaptation and variability in genomic regions that lack recombination. Y- or W chromosomes are particularly vulnerable to such effects, since they represent large, non-recombining blocks of genetic material. In birds, the W chromosome and mitochondrial genomes are both maternally transmitted, and hence fail to recombine with each other, whereas in mammals the Y chromosome is paternally transmitted. We show here that mitochondrial DNA sequence diversity is reduced in non-ratite birds compared with mammals. After considering possible confounding factors, such as differences in generation times, mutation rates and demography, we conclude that Hill-Robertson effects associated with the W chromosome provide the most likely explanation for this difference.

Evolutionary genetics. Clonal inheritance of avian mitochondrial DNA.

We have taken a new approach to test the commonly accepted, but recently questioned, principle of clonal inheritance of vertebrate mitochondrial DNA (mtDNA) by relating its inheritance to a female-specific marker of nuclear DNA. Whereas this is impossible in organisms with male heterogamy (such as mammals), we show here that genealogies of mtDNA and the female-specific W chromosome of a bird species are completely concordant. Our results indicate that inheritance of mtDNA is free of detectable recombination effects over an evolutionary timescale.

Imaging evaluation of suspected appendicitis in a pediatric population: effectiveness of sonography versus CT.

OBJECTIVE: The purpose of this study was to compare the diagnostic accuracy of graded compression sonography with that of helical CT for the diagnosis of appendicitis in a pediatric and young adult population. SUBJECTS AND METHODS: Between June 1996 and April 1999, 386 pediatric and young adult patients with suspected appendicitis were examined using sonography, CT, or both: 233 underwent sonography only, 71 underwent CT only, and 82 underwent sonography and CT. All sonograms and CT scans were prospectively interpreted as showing positive or negative findings for appendicitis by one of six pediatric radiologists. CT and sonographic findings were correlated with surgical and histopathologic findings or findings at clinical follow-up. RESULTS: Helical CT had a significantly higher sensitivity (95% versus 78%, p = 0.009) and accuracy (94% versus 89%, p = 0.05) than graded compression sonography for the diagnosis of appendicitis in children, adolescents, and young adults. The specificity of both techniques was 93%. Twenty of 82 patients who underwent both sonography and CT had discordance between the findings of the two examinations. The CT results were correct in a significantly greater number of patients with discordant examinations (17/20 patients [85%]). CONCLUSION: Helical CT has a significantly higher sensitivity and accuracy than graded compression sonography for the diagnosis of appendicitis in a pediatric and young adult population, particularly in children more than 10 years old.

Evaluation of suspected appendicitis in children and young adults: helical CT.

PURPOSE: To evaluate the accuracy of helical computed tomography (CT) for the diagnosis of appendicitis in children and to assess the utility of CT in establishing alternative diagnoses. MATERIALS AND METHODS: The medical records of 154 children (median age, 12 years; age range, 1-20 years) who were suspected to have appendicitis and who underwent CT were reviewed. The gastrointestinal tract was opacified in 151 of 154 patients: Only orally administered contrast material was used in 126 patients; only rectally administered contrast material, in 21 patients; and both oral and rectal contrast material, in four patients. CT findings were correlated with surgical and histopathologic findings or with clinical follow-up findings. RESULTS: Sixty-four CT scans were interpreted as positive for appendicitis and included 58 true-positive and six false-positive scans. Ninety scans were interpreted as negative and included 87 true-negative and three false-negative scans. CT had a sensitivity of 95% and a specificity of 94% for the diagnosis of appendicitis. In addition, in 32 (34%) of 93 patients without appendicitis, an alternative diagnosis was established on the basis of CT findings. CONCLUSION: Helical CT is useful in a pediatric population to diagnose or exclude appendicitis and to establish an alternative diagnosis.

Pulmonary hemorrhage: clinical course and outcomes among very low-birth-weight infants.

OBJECTIVE: To describe the clinical course, neonatal morbidity, and neurodevelopmental outcomes of very low-birth-weight (<1500 g) children who develop pulmonary hemorrhage. DESIGN: A retrospective case-control study in which 58 very low-birth-weight infants who developed pulmonary hemorrhage during 1990 through 1994, of whom 29 survived, were each matched to the next admitted infant who required mechanical ventilation for respiratory distress syndrome and was of the same sex, race, and birth weight (within 250 g). SETTING: A regional tertiary neonatal intensive care unit and follow-up clinic for high-risk infants at University Hospitals of Cleveland, Cleveland, Ohio. MAIN OUTCOME MEASURES: Survival, neonatal morbidity, and neurodevelopmental outcome at 20 months' corrected age. RESULTS: Pulmonary hemorrhage occurred in 5.7% of the total population of very low-birth-weight infants. Despite similar severity of lung disease, significantly more infants who developed pulmonary hemorrhage received surfactant therapy compared with controls (91% vs 69%, P = .005). Infants with pulmonary hemorrhage who died had a lower birth weight and gestational age compared with those who survived (766 g vs 1023 g; 25 weeks vs 28 weeks, P<.001) and more received surfactant therapy (100% vs 83%, P = .05). Survivors with pulmonary hemorrhage did not differ significantly from controls in rates of oxygen dependence at 36 weeks corrected age (52% vs 38%), grade 3 to 4 periventricular hemorrhage (28% vs 17%), or necrotizing enterocolitis (3% vs 7%), but tended to have more seizures (24% vs 3%, P = .05), periventricular leucomalacia (17% vs 0%, P = .06), and patent ductus arteriosus (79% vs 55%, P =.09). There were no significant differences in neurodevelopmental outcomes at 20 months' corrected age, (cerebral palsy, 16% vs 14%; subnormal [<70] Bayley Mental Developmental Index, 59% vs 43%; and deafness, 13% vs 10%). CONCLUSION: Although mortality is high, pulmonary hemorrhage does not significantly increase the risk of later pulmonary or neurodevelopmental disabilities among those who survive.

Small bowel obstruction in rats: diagnostic accuracy of sonography versus radiography.

Our purposes were to determine whether sonography can distinguish between obstructed and nonobstructed rats and to compare the diagnostic accuracy of sonography and radiography in the diagnosis of small bowel obstruction. Nonstrangulating small bowel obstruction was created in 19 rats; sham laparotomies were performed in 18 controls. Serial radiographs and sonograms, including duplex Doppler sonography, were obtained. Bowel diameter and bowel wall thickness were evaluated retrospectively. Bowel diameter, bowel wall thickness, and resistive indices increased in the animals with obstruction; controls remained unchanged (P = 0.002). Sonography demonstrated a significantly higher diagnostic accuracy than radiography at 24 hours and beyond (P = 0.023). Ultrasonography is sensitive and more accurate than radiography in diagnosing small bowel obstruction using objective criteria in the animal model.

Magnetic resonance imaging of the cardiovascular system and airway.

Cardiovascular MR imaging is unique in its ability to combine anatomic, physiologic, and functional information in a single examination. Established applications in the pediatric population include the evaluation of the child with a suspected thoracic aortic arch anomaly, vascular compression of the airway, coarctation of the aorta, pulmonary arterial and venous abnormalities, and cardiac or paracardiac masses. The increasing availability of radiologists with the knowledge and commitment to cardiac imaging will allow this exciting technique to thrive in the future, to the benefit of our patients.