Biomedical subjects

E R Barnes

Publications and source records attributed to E R Barnes.

3 recordsLinked to original sources

PubMed1995

Balance/excretion of 3H- and 14C-tyloxapol in the male rabbit after intratracheal administration.

1. Tyloxapol, trace-labelled (50-100 microCi/animal) with 3H or 14C, was administered intratracheally in a surfactant formulation (EXOSURF Neonatal) to the male rabbit in a total tyloxapol dose of 5 mg/kg. Urine, faeces, expired air, and blood were collected for up to 10 days following tyloxapol administration. 2. Over 5 days, 3H-tyloxapol-related radioactivity in the urine (13.4%) and faeces (27.4%) accounted for a major fraction of the labelled dose. However, urine also contained an additional 13% of the dose as tritiated water. Expired air accounted for only 4.2% of the dose. At the end of the study, an additional 35.6% of the radioactive dose was found in tissues and the carcass, mainly in the lung (27.4%) and to a lesser extent in the liver (2.8%) and kidney (0.4%). Levels of radioactivity in other tissues, including whole blood, were low. 3. Over a separate 10-day study, faecal (30.4%) and renal (9.7%) elimination of 14C-tyloxapol accounted for 40% of the radioactive dose, with expired air accounting for much less (2.7%). At the end of the study, additional radioactivity was recovered from the lung (43.9%) and to a lesser extent from the liver (3.8%) and kidney (0.3%). The half-life for the elimination of total radioactivity from the lung was estimated to be 10-12 days. 4. These data indicate that, following intratracheal administration, tyloxapol and metabolites were retained by the lung, released slowly into the systemic circulation, and eliminated through faecal and renal excretion.

Animals↗

PubMed1993

Antenatal phenobarbital to prevent or minimize intraventricular hemorrhage in the low-birthweight neonate.

OBJECTIVE: To review the evidence that antenatal phenobarbital can reduce the incidence or severity of periventricular-intraventricular hemorrhage (PIVH) in low-birthweight neonates. DATA SOURCES: MEDLINE searches were conducted with fan searches of all papers. STUDY SELECTION: Emphasis was placed on human data supplemented by relevant animal data. DATA SYNTHESIS: The barbiturates have been used to reduce hypoxic-ischemic cerebral events. Giving phenobarbital to high-risk pregnant women allows the drug to be in therapeutic concentrations during the critical period when PIVH occurs in low-birthweight infants. Current data suggest that antenatal phenobarbital can decrease the severity of PIVH; fewer data are available stating that it can decrease the incidence of PIVH. CONCLUSIONS: Evidence supports the hypothesis that antenatal phenobarbital is effective in decreasing the severity of PIVH in low-birthweight neonates. Further data are necessary regarding the incidence of low Apgar scores and respiratory depression in neonates given antenatal phenobarbital.

Cerebral Hemorrhage↗

PubMedDate not supplied

Codeine toxicokinetics in rats during a two-year dosed feed study.

Codeine toxicokinetics in F344 rats of both sexes were determined during a 2-year chronic toxicology study using dosed feed as the exposure route with a 12-hr light/dark cycle starting at 7:00 a.m. Rats were allowed to access to dosed feed formulations ad libitum with codeine concentrations at 0, 400, 800, and 1600 ppm. Blood samples were collected from individual rat on days 7, 21, and 90 at 7:00 p.m., 11:00 p.m., 3:00 a.m., and 7:00 a.m. Additional samples were collected at 16 and 24 months between 6:00-8:00 a.m. Plasma concentrations of codeine and morphine were determined directly by radioimmunoassay. Concentrations of their conjugates were determined indirectly by measuring the total amount of free codeine and morphine released after samples were treated with beta-glucuronidase. Results indicated that plasma concentrations of both codeine and morphine steadily decreased from day 7 to 16 months and then rebounded at 24 months. Results also indicated that plasma concentrations of both codeine and morphine correlated well with the amounts of codeine added to the feed. Bioavailability of codeine using the dosed feed route increased with dose, varying from 10% to 25%, which was somewhat higher than the previously reported approximately 8% bioavailability using the gavage route. Concentrations of conjugated codeine were very low, whereas concentrations of conjugated morphine were very high. These results suggested that demethylation of codeine to morphine in rats is the main metabolic pathway and was maintained over the course of the study.

Animals↗