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Biomedical subjects

T N Calvey

Publications and source records attributed to T N Calvey.

At least 55 records · Page 3Linked to original sources
PubMed1976

Plasma concentration of edrophonium in man.

The plasma concentration of edrophonium was measured in man after intravenous administration. In 5 patients, the clearance of edrophonium from the circulation during the 1-hr period of sampling was invariably resolved into 2 exponential components. An initial rapid phase of elimination from plasma (T/2 = 0.54 TO 1.92 Min) was followed by a much slower decline (T/2 = 24.23 to 45.00 Min), corresponding to the fall in concentration between 10 and 60 min. In parallel experiments in the rat, the clearance of 14C-edrophonium was resolved into 3 exponential components, although the final component could not be reliably defined until 1 to 3 hr after intravenous injection. It is suggested that the rapid fall in the plasma concentration of edrophonium in both species is not dependent on metabolism or excretion, but is due to the rapid uptake of the drug by the liver and kidneys.

Acetylcholinesterase↗
PubMed1976

The effect of edrophonium on erythrocyte acetylcholinesterase and neuromuscular function in the rat.

1. The relation between the concentration of edrophonium in plasma, inhibition of red cell acetylcholinesterase, and neuromuscular transmission was studied in the rat. 2. In both in vivo and in vitro conditions, red cell acetylcholinesterase activity was predictably related to the concentration of the quaternary amine. 3. After low doses of edrophonium (1.0 mumol/kg) there was a significant correlation between the monophasic potentiation of twitch tension and the plasma concentration of the drug. In contrast, with higher doses of edrophonium (4.0 or 10.0 mumol/kg) a biphasic potentiation of twitch tension was observed; this was only correlated with the plasma concentration of the drug during the secondary decline in neuromuscular facilitation. Subsequent recovery of normal neuromuscular transmission invariably occurred at a constant plasma concentration of edrophonium.

Acetylcholinesterase↗
PubMed1975

The effect of codeine phosphate on the absorption of ethyl alcohol.

The effect of syrup, B.P. and codeine phosphate syrup, B.P.C. on blood alcohol levels was determined in six normal subjects. 2 Treatment with syrup alone had little or no influence on the concentration of ethanol in blood. 3 In contrast, pretreatment with codeine phosphate syrup significantly reduced alcohol absorption, as assessed by the maximum blood levels achieved or the area subtended by the blood concentration-time curve. It is suggested that the diminished absorption of ethanol is related to the pharmacological action of codeine on the stomach. 4 It was considered that the concentration of ethanol in linctuses or syrups containing codeine was unlikely to have any significant effect on the central nervous system.

Codeine↗
PubMed1975

Bioavailability and dissolution of different formulations of oxytetracycline preparations.

1 The concentration of oxytetracycline in plasma was studied by microbiological assay after oral administration of five different preparations of the antibiotic. None of these preparations had been studied previously. 2 There was a statistically significant correlation between the time required for 50% dissolution at pH 2 and biological availability, as assessed by the peak plasma level or the area under the plasma concentration-time curve. 3 The mean bioavailability of oxytetracycline was greatest with preparations of the hydrochloride, and with film-coated tablets of the dihydrate. In contrast, sugar-coated tablets of oxytetracycline dihydrate were associated with poorer dissolution characteristics and reduced biological availability.

Biological Availability↗
PubMed1975

The pharmacokinetics of pyridostigmine and 3-hydroxy-N-methylpyridinium in the rat: dose-dependent effects after portal vein administration.

1 The elimination kinectis of [14C]-pyridostigmine iodine and [14-C-methyl]-3-hydroxypyridinium bromide (3-OH NMP) have been studied in the rat. 2 For pyridostigmine, at a given dose level, the fraction of the dose eliminated unchanged was reduced and the metabolite fraction was increased after portal vein administration when compared to jugular vein administration. This indicates that pyridostigmine is subject to metabolism during the first passage through the liver. 3 When doses of pyridostigmine 1.25 mumol/kg and higher were injected via the portal vein, the proportion excreted in urine as unchanged drug remained constant; in contrast, the percentage of the dose eliminated as the metabolite was significantly reduced. This indicates that a dose-dependent process is involved in the urinary excretion of 3-OH NMP. 4 This conclusion was supported by studies involving the portal and systemic venous injection of 3-OH NMP at different dose levels. After 4 h, approximately85% of the lowest dose was eliminated unchanged in ug this period. The proportion of the dose eliminated in urine was not related to the route of administration. 5 After the injection of pyridostigmine into the jugular vein, the initial rate of drug excretion fell rapidly for approximately 10 min; in contrast, after injection into the portal vein, the rate of excretion of the drug rose to a maximum at 30 minutes. This suggests that the hepatoportal system behaves as a distinct region during the distribution of this drug.

Animals↗
PubMed1974

The pharmacokinetics of (14C)-edrophonium in normal wistar rats and homozygous Gunn rats with ligated renal pedicles.

1 The distribution kinetics of [(14)C]-edrophonium were studied in both normal Wistar and homozygous Gunn rats with ligated renal pedicles.2 After intravenous injection the plasma concentration-time curve of [(14)C]-edrophonium was adequately fitted by a triexponential function in both species of rat and interpreted in terms of a three compartment model.3 The influence of the route of administration (i.e., systemic venous versus hepatic portal) of [(14)C]-edrophonium on its concentration in plasma was studied in normal Wistar rats with ligated renal pedicles. There was a marked difference in the area under the plasma concentration-time curve depending on the route of administration.4 The parameters of the model were determined and compared.5 The value of the metabolism rate constant was approximately the same in both species of rat. This suggests that the rate of conjugation of [(14)C]-edrophonium is unaltered in the homozygous Gunn rat despite the genetic lesion in UDP-glucuronyltransferase.

Animals↗
PubMed1972

The removal of 14 C-edrophonium from the circulation.

The clearance of (14)C-edrophonium from plasma was studied in the rat. Distribution studies showed that 5 min after intravenous injection of the drug, more than half the dose was present in the liver and the kidneys. The concentration in these organs was approximately 20 times the level in other tissues. The plasma concentration of (14)C-edrophonium was invariably expressed as the sum of two exponential terms, suggesting that the drug may return to the circulation from other tissues as the plasma level falls.

Animals↗
PubMed1972

Excretion of 14 C-edrophonium and its metabolites in bile: role of the liver cell and the peribiliary vascular plexus.

1. The metabolism and biliary excretion of (14)C-edrophonium chloride was studied in Wistar rat.2. Approximately 5% of the dose was recovered from bile in 6 hours. Most of the radioactivity was eliminated as (14)C-edrophonium glucuronide. Small amounts of the unchanged drug were also detected in bile, particularly during the first hour after administration of the drug.3. The concentration of (14)C-edrophonium glucuronide in bile was approximately 15-20 times its concentration in plasma.4. In contrast, the concentration of unchanged (14)C-edrophonium was similar in bile and plasma.5. Evidence is presented that unchanged (14)C-edrophonium is transferred from plasma to bile via the peribiliary vascular plexus.

Animals↗