Cross-polarization/magic-angle-spinning nuclear magnetic resonance in selectively 13C-labeled synthetic eumelanins

We report a solid-state NMR study of synthetic eumelanins prepared by oxidation of 5,6-dihydroxyindole (DHI) selectively 13C-labeled at positions 2 or 3 of the indole ring. The 13C-1H couplings have been used to quantify the carbons by selecting the non-protonated and protonated carbon resonances. By comparing the data of non-labeled melanin to that obtained using [2-(13)C]- and [3-(13)C]-enriched DHI, it was possible to clearly demonstrate the high chemical reactivity of position 2 and, to a lesser extent, position 3 of the DHI unit. These two sites together are responsible for three-quarters of the proton loss during polymerization. The cross-polarization/magic-angle-spinning spectra likewise point to a partial oxidation of positions 2 and 3 to the carboxyl and carbonyl oxidation states during the formation of melanin. Furthermore, it is shown that 13C-13C dipolar interactions in [2-(13)C]-enriched DHI melanins can be observed using radiofrequency-driven dipolar recoupling (RFDR) 2D experiments. An upper limit of about 4 A for the distance between the C-2 carbons is deduced from the RFDR experiments. This result is in agreement with the basic arrangement of the different atoms expected in the DHI melanins.

Levels of cadmium in kidney and liver tissues among a Canadian population (province of Québec)

In an exploratory study, levels of cadmium in whole-kidney and liver tissues of 314 subjects from the general population of the province of Quebec (Canada) were measured postmortem. Frequency distributions of cadmium concentrations were lognormal. As reported in similar studies, age and especially smoking habits were the main variables affecting cadmium concentrations. The geometric mean of whole kidney concentrations (wet weight) was 17.62 microg/g, with a minimum concentration of 2.25 microg/g and a maximum of 100.61 microg/g. Mean concentrations of cadmium in kidneys increased with age, reaching a plateau in the group 50 to 59 yr (29.49 microg/g), and falling slowly thereafter.

Antioxidant activity in bronchoalveolar lavage fluid from patients with lung cancer

Glutathione (GSH) is one of the key components of the lung antioxidant defenses. Chronic smokers have higher GSH concentrations in their epithelial lining fluid than do nonsmokers. The aim of this study was to compare antioxidant concentrations in epithelial lining fluid (ELF) from nonsmokers, smokers with, and smokers without non-small-cell lung cancer. The study found that GSH in ELF from patients with lung cancer was significantly greater than in ELF from smokers and nonsmokers, at 1,485.5 +/- 208, 544 +/- 97.6 microM, and 339.3 +/- 112 microM, respectively (p < 0.05). In contrast, superoxide dismutase (SOD) was lower in ELF from patients with lung cancer than in that from smokers and nonsmokers, at 3.52 +/- 0.99, 30.82 +/- 8.2, and 43.91 +/- 10.1 U/ml, respectively (p < 0.05). Spontaneous superoxide anion release by adherent alveolar macrophages (AM) showed no difference between smokers with and without lung cancer. These data indicate that patients with lung cancer have marked modifications in their ELF antioxidant defenses by comparison with those of smokers. It is difficult to distinguish whether changed antioxidant status is a primary disturbance involved in the cancer process or whether it is a consequence of the neoplastic changes in malignancy.

High-performance liquid chromatographic evaluation of 2-(alpha-thenoylthio)propionylglycine and its two metabolites in biological fluids

A high-performance liquid chromatographic (HPLC) method for determining 2-(alpha-thenoylthio)propionylglycine (TTPG) and its two main metabolites, thiophenecarboxylic acid and thiopronine, in biological samples was developed. TTPG and its metabolites were extracted by solvent partition and then determined by reversed-phase HPLC with UV detection at 245, 295 and 360 nm. This procedure was validated in order to allow the assay of these compounds in plasma and urine samples with sufficiently low detection limits (50 ng/ml for TTPG and TCA and 100 ng/ml for thiopronine) and with good linearity within the concentration range investigated. It was applied to a comprehensive pharmacokinetic investigation of TTPG in healthy volunteers.

[Pharmacokinetics of sulindac in aged patients presenting with inflammatory joint disease]

The kinetic of sulindac and its two metabolites (sulfide and sulfone) was investigated in twelve elderly patients, following multiple oral dose administration of 400 mg/d. Data were compared to those obtained previously in ten healthy volunteers who received the same dosage regimen. Following multiple dose administration, accumulation ratios indicate that sulindac do not accumulate either in elderly patients (R = 1.35; R = AUC0-24 J8/AUC0-24 J1) or in healthy young subjects (R = 1.38; R = U0-24 J1). No significant modification of sulindac and sulfide kinetic parameters was observed. The apparent bioavailability of the inactive metabolite, sulfone, was found to be doubled in elderly patients (p less than 0.05). We conclude that there is no need to modify the dosage regimen of Arthrocine (400 mg once a day) in elderly patients.

Mechanisms of chronotropic cardiac effects of alinidine and plasma concentration-response relationships in the conscious dog with chronic atrioventricular block

The chronotropic cardiac effects of alinidine were studied in the conscious dog with chronic atrioventricular block. Alinidine at 0.5 - 4 mg/kg, i.e., at plasma concentrations between 42 +/- 2 and 1625 +/- 371 ng/ml, initially increased atrial rate dose-dependently. This effect fell off rapidly, but atrial bradycardia was never observed. After atropine and pindolol, which raised basal atrial rate, alinidine (2 mg/kg) decreased atrial rate, whereas after phenoxy-benzamine, yohimbine or phentolamine, it produced atrial effects identical to those observed under basal conditions, i.e., initial tachycardia and no bradycardia. Alinidine dose-relatedly decreased ventricular rate. None of the pretreatments modified the maximal ventricular bradycardia, but interestingly after pindolol or yohimbine this effect developed more rapidly (maximal bradycardia between 3 and 5 against 30 min) and then declined progressively. Alinidine did not modify mean blood pressure at any dose. After atropine, phenoxybenzamine or phentolamine, alinidine remained without effect on mean blood pressure, but after pindolol or yohimbine, a hypotensive effect appeared concomitantly with the reduction of the ventricular bradycardia. These results show that the initial atrial cardioacceleration due to alinidine results from a direct vagolytic action of this drug and that the absence of atrial bradycardia results from buffering by the vagolytic effect and/or a relatively low basal atrial rate. They also suggest that the ventricular bradycardia does not involve either the muscarinic cholinoceptors or the alpha- or beta-adrenoceptors, though the results obtained after pindolol or yohimbine suggest possible involvement of a fall in sympathetic tone by stimulation of presynaptic or central alpha2-adrenoceptors, particularly in the persistence of the bradycardic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetics of cefatrizine administered in repeated doses]

Twelve healthy volunteers received cefatrizine orally at doses equal to 500 mg every 12 h for 5 days. Cefatrizine was assayed by high performance liquid chromatography in plasma and urines collected after the first and/or the last administration. Cefatrizine absorption was rapid; its peak plasma level was reached at time 1.79 +/- 0.07 h following the first dose, it was equal to 7.37 +/- 0.31 micrograms.ml-1. Its apparent elimination half-life was equal to 1.50 +/- 0.05 h, it explains the lack of accumulation with time during multiple administrations every 12 hours. Comparisons between peak plasma concentration and area under curves following the first and last dosing showed significant (p less than 0.01) but weak (close to 15%) reduction of these 2 parameters with time which could be explained by a slight reduction of cefatrizine absorption with time. In conclusion, cefatrizine does not accumulate when administered repeatedly at a dose equal to 500 mg every 12 h in young adult, and its pharmacokinetics is virtually linear with time.

A study of the interaction of roxithromycin with theophylline and carbamazepine

There have been reports of an interaction when theophylline and macrolides are given together, and also when carbamazepine is given with macrolides. We compared the kinetics of theophylline and carbamazepine, given alone and then in combination with roxithromycin. Roxithromycin had little effect on the pharmacokinetics of theophylline and none on carbamazepine, and roxithromycin can be given with either of the drugs without any need to alter the dose.

Quantitative analysis of S3341 in human plasma and urine by combined gas chromatography-negative ion chemical ionization mass spectrometry: 15 month inter-day precision and accuracy validation

A new quantitative assay for the determination of S3341, an alpha-2 agonist antihypertensive drug, has been developed using combined gas chromatography-negative ion chemical ionization mass spectrometry. The [M]-. ions from TFA derivatives of S3341 (m/z 276) and the internal standard (2H4)S3341 (m/z 280) are monitored simultaneously by selected ion monitoring. For S3341 concentrations ranging from the limit of detection (0.2 ng ml-1 using 1 ml of plasma) to 5 ng ml-1, the average assay precision (CV) is approximately 7% while the average assay accuracy (percentage of error) is 4%. Validation of the day-to-day precision and accuracy was realized after analysing control plasma samples (n = 295) concurrently with the biological samples collected during the pharmacokinetic studies conducted over 15 months. The average day-to-day precision (CV) and accuracy (percentage of error) are 10% and 6% respectively, thus indicating that this assay procedure routinely provides reliable analytical data.

[Comparative pharmacokinetics of piperacillin in young and elderly subjects]

One single 4 g dose of piperacillin was administered by intravenous infusion over 30 min to 15 patients aged from 66 to 90 years (mean +/- s.e.m.: 79.8 +/- 2.0 years); the patients mean weight was 53 +/- 4 kg. Fifteen samples of blood were withdrawn from each subject. Plasma piperacillin levels were measured by high performance liquid chromatography with detection in ultraviolet light at 214 nm. Mean plasma piperacillin concentrations in elderly subjects, measured 0.5, 2 and 12 h after dosing, were 168.5 +/- 15.7, 79.9 +/- 11.5 and 1.72 +/- 0.69 microgram.ml-1, as against 146.8 +/- 10.6, 35.5 +/- 3.9 and 0.212 +/- 0.040 microgram.ml-1 in healthy young adults. Plasma piperacillin concentrations versus time curves obtained after the infusion was discontinued were bi-exponential, with half-lives T1/2 (lambda 1) and T1/2 (lambda 2) of 0.65 +/- 0.11 and 1.72 +/- 0.09 h respectively; the corresponding figures in young adults were 0.59 +/- 0.03 and 1.81 +/- 0.13 h respectively). In elderly subjects the mean total clearance of piperacillin (ClT = 2.90 +/- 0.25 ml.min-1.kg-1) was reduced by 15% (NS) and the volume of distribution during steady state (Vdss = 0.337 +/- 0.027 L.kg-1) was increased by 43% (P less than 0.001). As a result, the mean time of piperacillin stay in the body (MRS = Vdss/Cl) was practically doubled in elderly subjects (2.09 +/- 0.15 h as against 1.15 +/- 0.04 h in young adults (P less than 0.01).

[Pharmacokinetics of ofloxacin in the elderly (65-85 years) with normal renal function after a single oral dose of 200 mg]

Ofloxacin is a fluoroquinolone that is mainly eliminated through the kidneys. We studied ofloxacin pharmacokinetics following administration of a single oral 200 mg dose to each of 16 elderly patients (77 +/- 2.4 years). Serum and urine concentrations were assayed using high performance liquid chromatography. Peak serum ofloxacin concentrations were 3.60 (+/- 0.36) micrograms/ml; residual concentrations were 1.33 (+/- 0.15) and 0.62 (+/- 0.10) micrograms/ml at 12 and 24 hours respectively. Urine concentrations approximating 100 micrograms/ml were found up to the 12th hour. As compared to healthy adults, in elderly subjects ofloxacin distribution volume (85.3 +/- 6.3 l) was decreased by 34%, apparent clearance (4.97 +/- 0.53 l/h) was divided by 2.6 and elimination half life (13.3 +/- 1.2 h) was almost doubled. A linear correlation was found between individual apparent ofloxacin clearances and creatinine clearances. In view of these significant changes in ofloxacin pharmacokinetics found in elderly subjects, we advocate reducing the usual dosage by half.

[Treatment of typhoid fever using ofloxacin. Clinical experience and determination of antibiotic diffusion into the mesenteric lymph nodes]

Nine patients with typhoid fever were given ofloxacin in a daily dosage of 400 mg for ten days. All patients recovered with no relapses. No case of Salmonella typhi carriage was recorded. Diffusion of ofloxacin into mesenteric lymph nodes was studied in four patients. Mean concentration was 1.46 micrograms/g after four 200 mg doses. According to our results, ofloxacin could be considered as one of the alternatives for treating typhoid fever.

Pharmacokinetics of pefloxacin after repeated intravenous and oral administration (400 mg bid) in young healthy volunteers

Multiple-dose kinetics of pefloxacin was determined in 12 normal male subjects given 400 mg pefloxacin by iv 1 h-infusion every 12 h for 16 doses. Twelve other subjects (6 men and 6 women) were given 400 mg pefloxacin by mouth every 12 h for 18 doses. Plasma and urine concentrations of pefloxacin and its main metabolites (N-desmethyl pefloxacin or norfloxacin and pefloxacin N-oxide) were measured by high performance liquid chromatography. The bioavailability of pefloxacin was complete and plasma concentrations after iv or oral administration were similar. Pefloxacin was rapidly absorbed from the gastrointestinal tract and reached maximum plasma concentrations about 1 h after dosing. Pefloxacin elimination (T 1/2 beta) increased from 11.00 +/- 2.64 h after the first iv dose to 13.93 +/- 3.58 h after the last iv dose (P less than 0.01). Apparent total body clearance decreased from 148.5 +/- 47.6 to 106.9 +/- 39.2 ml/min (P less than 0.01) because of decreased non-renal clearance (apparent volume of distribution did not significantly change over the repeated pefloxacin administration). Similar results were obtained after repeated oral dosing. Renal clearance of pefloxacin was low (7.47 +/- 2.28 ml/min) indicating that non-renal clearance represents the major route of elimination of this quinolone. Urinary excretion of pefloxacin and N-desmethyl and N-oxide metabolites was approximately 31% of the pefloxacin dose and beta-elimination half-lives of these metabolites were very close to that of pefloxacin (13.34 +/- 2.72 h and 11.95 +/- 2.64 h respectively). Due to a possible saturable process in the metabolic pathway, some accumulation occurred during repeated iv or oral treatment (accumulation ratio = 1.37 +/- 0.20). These results show that concentrations of pefloxacin in excess of the minimum inhibitory concentrations for many important pathogens can be rapidly achieved in plasma and urine with the 400 mg bid regimen with both iv and oral routes.

Cross-over study of the pharmacokinetics of cefonicid administered intravenously or intramuscularly to healthy adult humans

The pharmacokinetics of cefonicid were investigated in eight healthy adults. A one-gram dose was administered either intramuscularly or intravenously in a cross-over design study. Mean peak cefonicid plasma concentrations of 186 to 204 mcg/ml and 88 to 123 mcg/ml were achieved after intravenous and intramuscular injection, respectively, with elimination half-lives of 4.9 h and 5.3 h. Cefonicid concentrations were measured by both microbiological (M.A.) and high-performance liquid chromatography (HPLC) assays. Results were quite similar with the two techniques, except for the urinary recovery of cefonicid in the first 24 hours (83% of the dose with MA - vs 53% with HPLC method). The apparent volume of distribution (Vd area) was 0.18 1/kg; the total body clearance (CT) and the renal clearance (CR) were 24-26 ml/min and 15-19 ml/min, respectively. The kinetic data of cefonicid were not significantly different for the two routes of administration. A one-gram i.v. or i.m. cefonicid dose produced high and prolonged plasma concentrations with a longer half-life than obtained with commonly used cephalosporins.

Pharmacokinetics and bioavailability of viqualine, a new antidepressant

A high performance liquid chromatographic assay was developed for plasma and urine levels measurement of viqualine. The assay was used to study the disposition of 25 mg intravenous and oral single doses in five healthy subjects. Two exponential terms were required to describe the disposition of the drug after intravenous and oral administration. The bioavailability of oral viqualine averaged 80%. The mean apparent half-life was 12.1 +/- 1.9 and 11.9 +/- 1.4 h (mean +/- s.e.m., n = 5) after 25 mg I.V. and oral dose respectively. The apparent volume of distribution (Vdss) were 1578 +/- 132 1 (after I.V. administration) and 1572 +/- 201 1 (after oral administration). The body and renal clearances were respectively 1.56 +/- 0.31 1.h-1. kg-1 and 1.57 +/- 0.31 1.h-1. kg-1, after 25 mg bolus I.V.

[Pharmacokinetic behavior of cefsulodin and cefotiam alone or in combination after intravenous injection of 1 gram]

Simultaneous administration by the intravenous route of 1 g of cefotiam and 1 g of cefsulodin does not alter the pharmacokinetic parameters of either compound.

Pharmacokinetics of a fixed combination of sotalol and hydrochlorothiazide in hypertensive patients with moderate renal insufficiency

Decreased elimination of a combined formulation of Sotalol (160 mg) and hydrochlorothiazide (25 mg) was found in patients with moderate renal insufficiency. Very slight accumulation of sotalol and hydrochlorothiazide was observed, so it appears unnecessary to reduce the dosage in patients with a creatinine clearance of 30 ml/min or more.

Mass fragmentographic determination of timolol in human plasma and urine

A mass fragmentographic procedure was developed for measuring quantities of less than 1.0 ng of timolol/ml of plasma or urine. The lower limit of sensitivity was 0.5 ng of timolol maleate/ml of plasma. The unchanged drug was extracted into heptane--4% isopentyl alcohol from alkalinized plasma or urine, together with propranolol hydrochloride as the internal standard. The compounds were subsequently back-extracted into 0.1 N HCl and then into chloroform following adjustment of the acidic phase to an alkaline pH. The chloroform layer was evaporated to dryness, and the compounds were derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide-acetonitrile to form the trimethylsilyl derivatives; these derivatives were quantitated by mass fragmentography. Recovery of timolol added to normal plasma and urine was quantitative and reproducible, and no interfering substances were observed in normal biological samples. After a 20-mg oral dose of timolol maleate, plasma levels of approximately 3.0 ng/ml were observed at 12 hr.

Pharmacokinetics of oral timolol studied by mass fragmentography

The pharmacokinetics of timolol, after oral administration of single 20 mg doses to healthy subjects, has been studied using an original electron beam ionization GLC-mass spectrometry technique with computer -- controlled multiple ion detection. This method of mass fragmentography, tested with propranolol as an internal standard, permitted the measurement of timolol concentrations as low as 1 ng/ml with good precision and accuracy. It enabled the plasma level to be followed up to the twelfth hour after treatment. Individual variation was observed in bioavailability; the peaks plasma concentration (Cmax) of 50 to 103 ng/ml being achieved at different times(0.5--3h). The residual level after 12 h differed greatly between the subjects (0.8 to 7.2 ng/ml). The mean half-life of the terminal elimination phase was 2.62 +/- 0.17 h. Extra-renal elimination (metabolic and biliary) represented the main route of elimination, with a renal to body clearance ratio of 0.123. This level paralleled the percentage of unaltered timolol excreted in urine 24 h after its administration.

Fluorometric high-performance liquid chromatographic determination of sotalol in biological fluids

A high-performance liquid chromatographic (HPLC) method for sotalol in biological fluids is presented. Sample preparation involves a simple acid-base double-extraction procedure, and analysis is carried out on a reversed-phase chromatographic system using a muBondapak C18 column. Procainamide was used as the internal standard. As little as 20 ng of sotalol/ml can be detected with good precision by a fluorometric detector. HPLC, which allows more rapid analysis of plasma sotalol levels than does GLC, appears suitable for pharmacokinetic studies as well as for therapeutic drug monitoring.