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Biomedical subjects

R F Palmer

Publications and source records attributed to R F Palmer.

At least 37 records · Page 2Linked to original sources
PubMed1981

The metabolism of canrenone in vitro by rat liver preparations.

1. The metabolism of [1-3H]canrenone, a primary metabolite of spironolactone and potassium canrenoate, by rat liver preparations in vitro has been investigated. 2. Canrenone was metabolized by 3-oxo-delta 4-reduction to give 3 alpha-hydroxy-5 beta-spirolactones, and also by a number of O2 and NADPH-dependent microsomal hydroxylation reactions. 3. A major metabolic route requiring the presence of a microsomal fraction, but apparently independent of oxygen and NADPH, led to the formation of a number of compounds tentatively identified as trihydroxy-spirolactones.

Animals↗
PubMed1980

The effects of amrinone on contractility, Ca2+ uptake and cAMP in smooth muscle.

Amrinone, a known positive inotropic agent in the heart, was found to cause a dose-dependent (10--100 micrograms/ml) inhibition of norepinephrine (NE) or high-K+-induced contractions of rabbit aorta. Amrinone also inhibited carbachol or high-K+-induced contractions of guinea-pig taenia coli. Neither total tissue 45Ca uptake nor the rate of 45Ca uptake induced by 80 mM K+ in rabbit aorta was altered by pretreatment with amrinone. On the other hand, a similar pretreatment with amrinone inhibited NE (10(-6) or 10(-5) M) induced tissue 45Ca uptake. Amrinone (100 micrograms/ml) caused about a 70% increase in cAMP concentration over resting levels. It is concluded that amrinone causes a nonspecific inhibition of smooth muscle contractility by acting probably at multiple sites to decrease the availability of Ca2+ required for activation. One or more of these mechanisms may involve cAMP.

Aminopyridines↗
PubMed1980

A stable isotope dilution assay for disopyramide and its [13C, 15N]labelled analogue in biological fluids.

The mass spectra of disopyramide phosphate and two stable isotopically labelled analogues have been obtained using electron impact and chemical ionization. The low isotopic purity of [13C, 15N)disopyramide phosphate was shown to be due to the low isotopic purity of the 15N label. A stable isotope dilution assay for disopyramide and [13C, 15N]disopyramide in biological fluids has been developed using [2H14]disopyramide phosphate as the internal standard. This assay will be used to analyse samples obtained after the co-administration of disopyramide phosphate intravenously and [13C, 15N]disopyramide phosphate orally to several animal species.

Animals↗
PubMed1980

The absorption of disopyramide in animals determined using a stable isotope co-administration technique.

The stable isotope co-administration technique for estimating the bioavailability of drugs has been investigated in a series of experiments using rhesus monkeys. The compound chosen for study was disopyramide phosphate. A cross-over study was designed whereby the animals received disopyramide phosphate (administered intravenously at 5 mg kg-1) and [13C, 15N]disopyramide phosphate (administered orally at 5 mg kg-1), with a wash-out period between doses. A co-administration study was carried out whereby both the oral and intravenous doses were administered together. The co-administration study was repeated. The results from the cross-over study showed [13C, 15N]disopyramide to have an oral availability of 4.9 +/- 0.9% (by comparing areas under the plasma concentration versus time curves). The bioavailability was estimated to be 5.7 +/- 0.3% comparing totals excreted in urine over 48 h. The bioavailability of the oral dose was calculated as 8.2 +/- 2.5% (comparing areas under plasma concentration versus time curves) and 9.3 +/- 3.0% (comparing totals excreted in urine) after co-administration. The differences between these results and the cross-over results were examined in a further study, using oral administration only. The animals were dosed orally with a solution containing both disopyramide phosphate (5 mg kg-1) and [13C, 15N]disopyramide phosphate (5 mg kg-1). No differences were observed between the plasma concentration versus time curves or urinary excretion for either isotope. It is unlikely that the discrepancy in bioavailability is due to absorption, metabolism or exretion of the oral dose. It is probable that the high concentration of disopyramide obtained after the intravenous dosage affects the disposition of the oral dose, and this gives the higher figure.

Administration, Oral↗
PubMed1980

Plasma levels and urinary excretion of orally administered propantheline bromide in man.

After a single oral dose of 30 or 60 mg of propantheline bromide peak plasma levels of the drug were reached within 2 h in six healthy men. Mean peak plasma concentrations were 20.6 and 53.1 ng/ml after 30 mg and 60 mg respectively. The mean apparent absorption and elimination half-lives after 30 mg dose were 0.22 and 1.57 h respectively, and similar half-lives were found at the higher dose level. There was a dose related change in plasma levels and AUCinfinity of the drug, and some 3% to 4% of the administered dose of propantheline bromide was excreted unchanged in urine at each dose level. Comparison of the plasma levels and urinary excretion of the drug with those seen after i.v. administration in an earlier study indicated an apparently low systemic availability of orally administered propantheline bromide. There was tentative evidence of a qualitative relationship between the oral dose administered, plasma concentrations and the effects of propantheline bromide on salivary excretion.

Administration, Oral↗
PubMed1980

Disposition of pranolium chloride in small mammals.

The disposition of [14C]pranolium chloride, a dimethyl quaternary derivative of propranolol, has been studied in rats, mice and hamsters after oral parenteral dosage. 2. Elimination of 14C occurred largely via the kidneys after parenteral dosage, but biliary excretion was significant. Pranolium chloride was excreted unchanged and as a conjugate, and was also metabolized to 1-naphthol which was conjugated. 3. The radiolabel was localized in the liver, kidneys, heart, lungs and gastro-intestinal tract of the rat, but did not pass the placental or blood-brain barriers to any appreciable extent. Unchanged pranolium chloride was localized in rat cardiac tissue for at least 6 h after i.v. dosage. 4. Pranolium chloride was poorly and variably absorbed from the gastro-intestinal tract of animals. Peak plasma levels occurred between 10 min and 1 h. The absorption of the pranolium cation was marginally increased after prolonged fasting, but was not affected by the presence of alternative anions.

Animals↗
PubMed1980

Metabolism of ethynodiol diacetate in the rhesus monkey before and after administration of rifampicin.

1. On administration of a single oral dose of [4-(14)C]ethynodiol diacetate (0.15 mg/kg) to rhesus monkey, plasma concn. of total 14C peaked after about 4 h. About 60% of the plasma radioactivity was present as glucuronide conjugates and no unchanged drug was detected. 2. Some 67 +/- 6% (mean +/- S.D.) of the dose of 14C was excreted in 4 days, 50 +/- 6% in urine and 18 +/- 2% in faeces. Most of the urinary excretion occurred within 24 h of dosage. 3. Glucuronide conjugates accounted for 60% of the urinary 14C, and 46% of the faecal 14C was free steroids. 4. Norethisterone and its tetrahydro metabolites were identified in the free, glucuronide and sulphate fractions of plasma and urine. Keto-4,5-dihydronorethisterones and trihydroxy metabolites were identified in the conjugated fractions of urine, and a complex mixture of polar metabolites was detected in faeces. 5. Rifampicin treatment (7.5 mg/kg/day, orally) for 8 days decreased the half-life of total 14C in plasma following a single oral dose of 4-[14C]ethynodiol diacetate (0.15 mg/kg) from 44 +/- to 24 +/- 2 h. 6. Faecal elimination of total 14C was significantly increased to 29 +/- 5% of the dose following rifampicin treatment, but urinary excretion was unchanged. 7. Rifampicin treatment increased the amount of polar metabolites and decreased the amount of norethisterone in the free and conjugated fractions of plasma and urine. The amounts of sulphate and non-hydrolysed conjugates in faeces were increased after rifampicin treatment.

Animals↗
PubMed1979

Bioavailability and pharmacokinetics of norethisterone in women after oral doses of ethynodiol diacetate.

Measurement by radioimmunoassay of plasma norethisterone (NE) has been used to compare the bioavailability of tablets containing ethynodiol diacetate (EDA) with that of a standard oral solution of this progestogen in 12 normal women. The tablets investigated were from three batches which showed different in vitro dissolution rates. There were no significant differences in the bioavailability of the tablet formulations, which were essentially bioequivalent to the solution. Peak blood levels of NE were reached within 4h of EDA administration in solution or tablets. After the peak, NE plasma levels declined in two phases, with a mean terminal elimination half lives of 4 to 6.9h. The pharmacokinetics of NE after EDA administration showed some similarity to those observed by other workers after oral doses of NE itself.

Adult↗
PubMed1979

The use of 22Na as a tracer for long-term bone mineral turnover studies.

Sodium-22 has been studied as a tracer for bone mineral metabolism in rats and dogs. When incorporated into bone during growth from birth to adulthood, the bone becomes uniformly tagged with 22Na, which is released through the metabolic turnover of the bone. The 22Na not incorporated in the bone matrix is rapidly excreted within a few days when animals are fed high, but nontoxic levels of NaCl. The 22Na tracer can be used to measure bone mineral loss in animals during space flight and in research on bone disease.

Adult↗
PubMed1978

Application of ion-exchange and lipophilic-gel chromatography to the purification and group fractionation of steroidal spirolactones, isolated from biological fluids.

Chromatography of steroidal spirolactones on DEAE-Sephadex A-25 under selected pH conditions allowed efficient separation of these compounds from other steroids and many of the endogenous components of human urine. The spirolactones were recovered in high yield, mostly over 90%. Lipophilic-gel chromatography provided a useful method for group fractionation of mixtures of these spirolactones with high recoveries (generally over 90%), unaffected by the presence of endogenous material from normal human urine.

Canrenoic Acid↗
PubMed1978

Electron impact and chemical ionization mass spectrometry of steroidal spirolactones.

Electron impact and chemical ionization mass spectra are reported for several steroidal spirolactones and their TMS ethers. The electron impact spectra were characterized generally by low abundance molecular ions and large numbers of fragment ions. Methane chemical ionization spectra exhibited high intensity [M+H]+ and/or [M+H-H2O]+ or [M+H-TMSOH]+ ions with few other fragment ions. Ammonia chemical ionization spectra had intense [M+H]+ and/or [M+NH4]+ ions with a few fragment ions generally formed by loss of H2O or TMSOH from these parent ions. Ammonia chemical ionization gave intense parent ions even for polyhydroxy compounds and their TMS ethers in contrast to methane chemical ionization. The results of this study suggest that a combination of electron impact with ammonia chemical ionization mass spectrometry would offer the best techniques for detection and identification of these compounds in biological fluids.

Ammonia↗
PubMed1978

Endocrine effects of spironolactone in man.

A double blind, controlled study was carried out in order to investigate the effects of administering spironolactone, 200 mg daily, to five healthy male volunteers. The patterns of change in plasma testosterone (T) and luteinizing hormone (LH) after spironolactone were significantly different from placebo and there were significant increases in the urinary excretion of androsterone (A), aetiocholanolone (EC) and total oestrogen. Urinary dehydroepiandrosterone (DHA) excretion, after an initial rise, declined progressively during the treatment period relative to controls. The results are discussed in the light of previous observations. It is concluded that treatment with spironolactone for 2--4 days will lead to a transient rise in plasma T and urinary DHA. Continued treatment (4--10 days) is thought to cause increased LH secretion, with normalization of plasma T and DHA excretion. These changes are accompanied by increased androgen catabolism and a slightly increased conversion of androgens to oestrogens. Healthy men may therefore show alterations in sex steroid metabolism if treated for several days with high doses of spironolactone.

17-Ketosteroids↗
PubMed1978

Identification of some urinary metabolites of propantheline bromide in man.

The peak plasma concn. of total radioactivity occurred 6 h after a single oral dose of [carboxyl-14C; methyl-2H3] propantheline bromide was administered to a healthy man. At this time 10% of the dose was present in the total plasma volume. 2. A total of 71% dose of radioactivity was excreted in urine in 96 h after dosage, 59% dose being excreted in the first 24 h. About 5.3% of the orally administered propantheline bromide was excreted unchanged. 3. T.l.c. analysis and g.l.c.-mass spectrometry showed xanthanoic acid, hydroxyxanthanoic acid(s), and propantheline as urinary metabolites of the drug. 4. A glucuronide of xanthanoic acid, a hydroxylated propantheline and the (2-hydroxyethyl)diisopropylammonium ion were tentatively identified as urinary metabolites. Hydrolysis of propantheline and conjugation of the resulting xanthanoic acid appear to be the major routes of metabolism of this compound. 5. A mean elimination half-life of 9.2 h was obtained for the total radioactivity by pharmacokinetic analysis of plasma and urine levels of 14C.

Adult↗