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Biomedical subjects

A R Beaubien

Publications and source records attributed to A R Beaubien.

10 recordsLinked to original sources
PubMed1991

Evidence that amikacin ototoxicity is related to total perilymph area under the concentration-time curve regardless of concentration.

Previous studies have failed to fully establish whether ototoxicity is related in any way to the levels of an aminoglycoside antibiotic in the perilymph. To study this we exposed guinea pigs to continuously infused amikacin at four different dosing rates under conditions parallel to those used in our previous study which related ototoxicity to total plasma area under the concentration-time curve regardless of the level in plasma. It was found that at all dosing rates, levels in the perilymph and ratios of levels in perilymph/plasma remained constant as the dosing duration increased from nonototoxic to strongly ototoxic. Plasma and perilymph amikacin levels were found to be linear functions of the dosing rate even at ototoxic dosing exposures, and ratios of levels in perilymph/plasma did not differ between dosing rates. The total perilymph area under the concentration-time curve was not different between dosing rates either for a total dose associated with threshold ototoxicity or for one associated with severe ototoxicity. The results suggest that amikacin ototoxicity is related to the integral of the concentration in the perilymph over the total time of amikacin exposure regardless of the level in the perilymph.

Amikacin↗
PubMed1977

Effect of subacute dosing and phenobarbital and 3-methylcholanthrene pretreatment on the metabolism of acetaminophen in rats.

The metabolism of 14C-ring-labelled acetaminophen was studied in male Wistar rats. Pretreatment with phenobarbital increased the initial rate of elimination of 14C from the blood and increased the amount of acetaminophen glucuronide excreted in the urine. Pretreatment with 3-methylcholanthrene did not significantly affect the rate of elimination from the blood and decreased the amount of acetaminophen glucuronide in the urine. Daily dosing with acetaminophen for up to 3 weeks increased the rate of elimination of 14C from the blood after 4 h, and increased the urinary excretion of both total 14C and the glucuronide and sulfate conjugates. Subacute dosing with acetaminophen had a diuretic effect but this did not correlate with the increased excretion of the drug. It is concluded that acetaminophen elimination is increased by phenobarbital pretreatment and by subacute dosing with acetaminophen, but by different mechanisms.

Acetaminophen↗
PubMed1977

Subacute imipramine: changes in single dose pharmacokinetics in rats.

Imipramine (10 mg/kg, p.o.) administered to male Wistar rats (133-178 g) twice daily for 3 weeks more than halved the control rate of body weight gain. A bile fistula was inserted after this period and 14C-imipramine (10 mg/kg, p.o.) was administered 14-18 hr after the final scheduled dose. Biliary excretion of radioactivity during the subsequent 50 min was decreased to 16% of control. Higher levels of gastrointestinal radioactivity (mainly in the stomach lumen) indicated a slower imipramine absorption rate in the subacute group. Liver metabolite ratios revealed that the treatment group had decreased rates of 2-hydroxylation and 10-hydroxylation, but not demethylation, of imipramine. After incubation of the 25-50 min bile sample with glusulase, bile-to-liver ratios of metabolites indicated a lower entry rate of imipramine, desmethylimipramine and 2-hydroxydesmethylimipramine, but not of 2-hydroxyimipramine or 10-hydroxyimipramine, into bile of the subacute imipramine group.

Administration, Oral↗
PubMed1977

Effects of phenobarbital and diazepam on imipramine-induced changes in blood pressure, heart rate and rectal temperature of rats.

To investigate the safety of anticonvulsants in doses found equipotent in suppressing imipramine induced convulsions, the effects of diazepam (1.8 mg/kg) or phenobarbital (40 mg/kg) following a toxic dose of imipramine (50 mg/kg) on heart rate, blood pressure and body temperature were examined in male Wistar rats. Administration of imipramine alone resulted in significant decreases in blood pressure, heart rate and rectal temperature. Phenobarbital or diazepam alone failed to significantly affect any of these parameters apart from a slight reduction in rectal temperature seen with phenobarbital. Diazepam given after imipramine antagonized the imipramine-induced decrease in heart rate but increased the hypotensive and hypothermic effects. Phenobarbital failed to significantly affect the imipramine-induced changes in any of the physiological parameters studied. The present data suggests that phenobarbital may be preferable to diazepam in treatment of imipramine-induced convulsions.

Animals↗
PubMed1976

Imipramine enhancement of pentobarbital toxicity in rats.

The toxicity of pentobarbital was examined in male Wistar rats pretreated with a non-toxic dose of imipramine (10 mg/kg, po). Pentobarbital (70 mg/kg, ip) lethality was enhanced up to 6 hr after imipramine administration, and pentobarbital (45 mg/kg, ip) sleeping time was prolonged up to 12 hr after imipramine. Physiological measurements showed that imipramine pretreatment 2 hr prior to pentobarbital (70 mg/kg, ip) enhanced barbiturate depression in mean blood pressure, oxygen consumption and respiration rate, but not in heart rate or back skin temperature. Analysis of brain radioactivity after [14C] pentobarbital indicated that these effects of imipramine were not solely the result of inhibition of liver metabolism.

Animals↗
PubMed1975

Effects of thioridazine and diazepam on the pharmacokinetics of [14C]imipramine in rat: acute study.

The pharmacokinetics of [14C]imipramine (10 mg kg minus 1) were tested in male Wistar rats for interaction with thioridazine (16 mg kg minus 1) or diazepam (10 mg kg- minus 1). All drugs were administered orally with the test substances being given 40 min before [14C]imipramine dosing. Bile and urine were collected for 90 min after the radioactive drug was given. The animals were then killed and the tissues removed. Thioridazine reduced the excretion of radioactivity into the bile and urine, and increased the weight of the contents within the gastrointestinal tract. These effects were interpreted as being mainly due to a reduction in gastrointestinal motility resulting in a slower stomach emptying of [14C]imipramine. No effect on metabolism was detected. Diazepam pretreatment reduced the concentration ratio of radioactivity in the small intestinal contents to that of plasma, but did not alter the tissue distribution, metabolism or excretion of [14C]imipramine.

Animals↗