Inhibition of cholinesterases by histamine 2 receptor antagonist drugs.

Many studies have demonstrated that histamine 2 receptor antagonists (H2RA) have in vitro anticholinesterase effects, but discrepancies about type and potency of this inhibitory effect exist among published results. Moreover, cholinesterase inhibition has not been shown in patients receiving H2RA. These discrepancies led us to study the in vitro antibutyryl- and in vitro antiacetylcholinesterase activities of ranitidine, cimetidine, nizatidine comparatively to pyridostigmines. Plasma cholinesterase activity (PCEA), erythrocyte cholinesterase activity (ECEA) and plasma ranitidine levels were measured in six patients before and during continuous IV infusion (150 or 200 mg/d) of ranitidine. Our in vitro results confirm the weak anticholinesterase activity of H2RA. Ranitidine is the most potent inhibitor of butyrylcholinesterase (Ki = 61 microM). Ranitidine and nizatidine are the most potent inhibitors of acetylcholinesterase (Ki' = 2.1 microM, Ki' = 5.1 microM, respectively) but one thousand times less effective than pyridostigmine (Ki = 0.003 microM). The results in patients show no statistically significant difference between PCEA and ECEA measured before and during ranitidine infusion (plasma ranitidine levels between 0.31 and 1.25 microM).

Toxicological screening of drugs by microbore high-performance liquid chromatography with photodiode-array detection and ultraviolet spectral library searches.

We use ultraviolet data, acquired with a photodiode-array detector coupled to a reversed-phase liquid-chromatographic system, to identify unknown drugs in plasma samples of acutely poisoned patients. Both retention time and spectra of the peaks obtained with a microbore Hypersil ODS column under gradient elution are compared with a library of approximately 350 compounds. We present our three-year experience with this system, which identifies drugs in less than 1 h, with a high degree of confidence.

Effects of an EDTA infusion on the urinary elimination of several elements in healthy subjects.

Ethylene diamine tetraacetate calcium disodium salt (EDTA Ca Na2), 1 g dissolved in 250 ml of 5% w/v glucose solution, was infused intravenously over 1 h into 10 healthy subjects (eight males and two females). Urines were collected over 24 h, the day before and on the day of the EDTA Ca Na2 infusion test. The elements Al, B, Ba, Cu, Fe, Mn, Si, Sr, Zn, Na, K, Ca, Mg, S and P were measured by inductively coupled plasma optical emission spectrometry. Pb was measured by inductively coupled plasma mass spectrometry. The EDTA Ca Na2 infusion increased the 24 h elimination of Al from 9.8 micrograms to 58 micrograms, of Fe from 66 to 121 micrograms, of Mn from 2.9 to 16.5 micrograms, of Pb from 9.8 to 56 micrograms and of Zn from 623 to 8847 micrograms. The ratio of the increase of urinary elimination induced by EDTA Ca Na2 was about 2 for Fe, 5 for Al, Pb and Mn, and 15 for Zn.

Urinary elimination of molybdenum by healthy subjects as determined by inductively coupled plasma mass spectrometry.

The concentration of molybdenum was measured by inductively coupled plasma mass spectrometry (ICPMS) in the urines of two groups of healthy people living in two areas of France, Brest and Paris, about 500 km away. The concentration of Mo in the 24-hour urines of 10 healthy subjects from the Brest region was 25 +/- 10 micrograms/l, 38 +/- 20 micrograms/24 h and 21 +/- 9 micrograms/g creatinine. The concentration of Mo in the morning urines of 23 healthy men of the Paris region was 41 +/- 34 micrograms/l and 21 +/- 15 micrograms/g creatinine. Thus the mean elimination of Mo per gram of creatinine was the same in the two groups (21 +/- 9 and 21 +/- 15). Since the three main isotopes of Mo m/z = 95, 96 and 98, corresponding to an abundance percentage of 16, 17 and 24.5, respectively, were simultaneously analyzed in each sample and led to similar results, the ICPMS method seems reliable.

Automated fluoroimmunoassay of theophylline and valproic acid by flow-injection analysis with use of HPLC instruments.

For automated determination of theophylline and valproic acid by use of Ames' fluoroimmunoassays we used a high-pressure liquid-chromatographic system consisting of a pump, a robotic unit (Gilson 231/401, to prepare and inject the samples into the flowing carrier), and a fluorometer with a 10-microL flow cell. Results correlated well with those of conventional liquid- and gas-chromatography (r less than 0.96). The between-run CV is about 5%. In comparison with the manual method, the volume of reagents (and thus the cost per analysis) was decreased by eightfold.

Screening for neutral and basic drugs in blood by dual fused-silica column chromatography with nitrogen-phosphorus detection.

We describe a capillary gas-chromatographic method for detection and quantification of basic and neutral drugs in the plasma of patients thought to be poisoned after dangerous overdose. Without further derivatization, the drugs are extracted from 1 mL of plasma, at basic pH, into diethyl ether. The extracts are injected onto two fused-silica capillary columns of different polarity (Ultra 1 and CP Sil 19 CB) coupled to nitrogen-phosphorus detectors. Under these conditions, drug-free plasmas give blank chromatograms, with a peak only for the internal standard (RN 927, an antihistamine not being marketed). Plasma samples from patients who have taken drugs show additional peaks, the relative retention times (RRTs) of which are used to identify the drugs. Here we list the RRTs of about 200 drugs on the two columns. Analyses are routinely performed with an automatic injector; overall analysis time is about 1 h per sample. During the last six years, more than 1000 plasma samples per year have been analyzed. We find this method a powerful tool for toxicological analysis, especially in cases of multi-drug intoxications.

Cyanide and thiocyanate blood levels in patients with renal failure or respiratory disease.

Whole blood cyanide and plasma thiocyanate were measured by a headspace gas chromatographic method and a colorimetric method, respectively, in 16 healthy subjects, in 10 patients with respiratory disease and in 12 patients on chronic dialysis for renal failure. In healthy subjects, whole blood cyanide and plasma thiocyanate concentrations were significantly higher in smokers (1.8 +/- 0.4 mumol/l; 206 +/- 74 mumol/l) than in non-smokers (0.8 +/- 0.4 mumol/l; 74 +/- 19 mumol/l). In renal failure patients on hemodialysis, no difference was noted in cyanide levels (0.6 +/- 0.4 mumol/l), but there was a significant increase in plasma thiocyanate levels during the interdialysis period (62 +/- 24 mumol/l; 91 +/- 24 mumol/l). No difference in cyanide and thiocyanate levels of patients with respiratory disease was seen, in agreement with a weak pulmonary elimination of cyanide.

[Level of urinary phenol and hippuric acid in control subjects and subjects exposed to benzene and toluene]. / Dosage du phénol et de l'acide hippurique urinaires chez des témoins et des sujets exposés au benzène et au toluène.

Two high-performance liquid chromatographic methods are described, one for assay of phenol in urine, the other for assay of hippuric acid. Steam distillation was used to hydrolyse the sample and separate the phenol from the matrix. A dilution was the only pretreatment of urine for assay of hippuric acid. The upper reference limits obtained from 42 non-exposed subjects were 7.09 mmol/mol creatinine for urinary phenol and 1,174 mmol/mol creatinine for hippuric acid. The mean concentration of urinary phenol was higher in 190 exposed workers (7.21 +/- 5.05 mmol/mol creatinine; mean +/- SD) than in control subjects (3.97 +/- 1.56 mmol/mol creatinine).

[Plasma concentration of noradrenaline in essential arterial hypertension]. / Concentration plasmatique de noradrénaline dans l'hypertension artérielle essentielle.

Plasma norepinephrine concentrations after supine rest and after standing were measured by high-pressure liquid chromatography with electrochemical detection in 49 normotensive controls and in 79 patients with essential hypertension. Twenty-nine hypertensive patients were not treated for hypertension. In normotensive subjects--but not in hypertensive patients--supine plasma norepinephrine levels increased significantly with age. No significant difference in supine plasma norepinephrine levels was found between hypertensive patients (NE = 0.28 +/- 0.16 microgram/l, n = 79 and NE = 0.28 +/- 0.14 microgram/l, n = 29) and normotensive subjects (NE = 0.30 +/- 0.13 microgram/l). When expressed as percentage, the rise in norepinephrine levels when standing was greater in hypertensive patients (127.4 +/- 77.4%, n = 79 and 122.6 +/- 65.6%, n = 29) than in normotensive subjects (93.2 +/- 60.3%). When patients and controls aged less than 40 years were compared, similar results were obtained. Supine plasma norepinephrine levels do not support the theory that sympathetic system activity is enhanced in essential hypertension.

[Plasma noradrenaline in hyperthyroidism and hypothyroidism]. / Noradrénaline plasmatique dans l'hyperthyroïdie et l'hypothyroïdie.

Plasma noradrenaline concentrations (NA) were measured in 11 hypothyroid patients, 24 hypothyroid patients and 30 normal subjects after 30 minutes of supine rest and after 5 minutes of standing. Observed noradrenaline levels, after rest as well as after standing, were significantly higher in hypothyroid patients (NA rest = 0.66 +/- 0.35 microgram/l, NA standing = 1.26 +/- 0.70 micrograms/l) and significantly lower in hyperthyroid patients (NA rest = 0.22 +/- 0.13 micrograms/l, NA standing = 0.37 +/- 0.20 microgram/l) than in normal subjects (NA rest = 0.32 +/- 0.13 microgram/l, NA standing = 0.55 +/- 0.20 microgram/l). The increase in noradrenaline with standing, when expressed in percent, was similar for the three groups studied (about 100%). These results suggest that a sympathetic nervous system adaptation occurs in hyperthyroidism and hypothyroidism as a compensatory phenomenon to the direct effect of thyroid hormones on the heart.

Normal reference intervals for free catecholamines and their acid metabolites in 24-h urines from children, as determined by liquid chromatography with amperometric detection.

We used two methods of reversed-phase liquid chromatography with amperometric detection, one for assay of unconjugated norepinephrine, epinephrine, and dopamine in urine, the other for determination of unconjugated vanillylmandelic acid and homovanillic acid. The catecholamines were extracted from urine by passage through a weak-cation exchange resin, then through alumina. Vanillylmandelic acid and homovanillic acid were isolated from urine by a two-step solvent-extraction procedure. The between-day CV was 5% for norepinephrine, 3% for epinephrine, 3% for dopamine, 4.5% for vanillylmandelic acid, and 6.4% for homovanillic acid. Reference ranges for these analytes in 76 children, ages 3-16 years, are reported.

[Pharmacokinetics of thiopental in women and newborn infants]. / Pharmacocinétique du thiopental chez la femme et le nouveau-né.

Plasma thiopentone concentrations after a single intravenous dose were determined by high pressure liquid chromatography in female surgical patients (n = 13), in pregnant women at term (n = 13) and in neonates (n = 13). In pregnant women, the apparent volume of distribution (Vd = 10.02 +/- 3.26 l X kg-1), plasma clearance (Cl = 22.03 +/- 7.55 l X h-1) and elimination half-life (t 1/2 (3) = 21.71 +/- 11.12 h) were significantly greater than in the surgical patients (Vd = 4.22 +/- 1.16 l X kg-1; Cl = 12.49 +/- 3.50 l X h-1; t 1/2 (3) = 13.79 +/- 3.09 h). Elimination half-life in neonates (t 1/2(e) = 17.9 +/- 9.7 h) was not different from half-life in mothers or in the surgical group. At delivery, the simultaneous concentrations were 5.3 +/- 1.3 mg X l-1 in venous blood and 3.8 +/- 1.6 mg X l-1 in cord venous blood. Apgar score was 10 in eleven neonates. For two babies, an Apgar score at 6 was explained by a uterine incision-to-delivery time interval greater than 2 min.

Thiopental pharmacokinetics under conditions of long-term infusion.

Thiopental was used in long-term infusion (3-4.5 mg . kg-1 . h-1 during 4-8 days) to protect the brain from injury following trauma. Thiopental plasma concentrations were measured during infusion (48 patients) and after infusion (14 patients) to determine the kinetics of the drug in continuous infusion. All mean values were mean +/- SD. Steady state concentrations (Css) were 31.8 +/- 10.7 mg/l for an infusion rate of 3.05 +/- 0.37 mg . kg-1 . h-1 and 48.9 +/- 14.6 mg/l for a rate of 4.2 +/- 0.3 mg . kg-1 . h-1. Corresponding steady state clearance decreased when Css increased, indicating possible saturation of the metabolic enzymatic system. Michaelis-Menten kinetics were confirmed by postinfusion data that give, for higher Css, a nonlinear decay of log C versus time. First-order kinetics were only obtained with Css below 30 mg/l. The maximum rate of elimination (Vm) was 1.76 +/- 1.15 mg . l-1 . h-1 (n = 11), and the Michaelis constant (Km) was 26.7 +/- 22.9 mg/l (n = 11). Hepatic enzyme saturation was between 35 and 85%. The volume of distribution at steady state was 4.35 +/- 1.83 l/kg (n = 11). Apparent half-lives of elimination were between 18 and 36 h at the end of infusion, and predicted terminal half-lives were 10.15 +/- 5.43 h (n = 11). Phases of burst-suppression were observed on electroencephalographic traces for concentrations greater than 40 mg/l. The authors' results suggest that a continuous infusion at a dose of 4 mg . kg-1 . h-1 induces EEG changes consistent with a near-maximum reduction in cerebral metabolism. Because of the thiopental Michaelis-Menten kinetics at doses above 4 mg . kg-1 . h-1, the authors suggest that thiopental plasma concentrations be measured and/or the drug effect be measured with the EEG to prevent excessive thiopental overdosage, causing a prolonged recovery time.

[Plasma catecholamine concentrations during exercise in the untrained subject and in the sportsman]. / Concentration plasmatique de catécholamines à l'effort chez le sujet non entraîné et chez le sportif.

Plasma noradrenaline (NA) and adrenaline (A) concentrations were measured by high liquid pressure chromatography in five untrained subjects and in five well-trained rowers during an exercise test on bicycle ergometer. Blood samples were collected, via a venous catheter, at rest, after standing 5 minutes, at maximal work level and at 5, 10, 20 minutes of post-exercise. Plasma NA and A concentrations at rest and after 5 minutes of standing were similar in the two groups. At maximal work load (340 +/- 38 for rowers and 220 +/- 11 W for untrained subjects), for a same pulse rate (178.0 +/- 7.6 for rowers and 176.6 +/- 4.7 beats/minutes-1 for untrained subjects), NA and A concentrations were higher in athletes (NA: 5.57 +/- 1.32 microgram/l; A: 0.95 +/- 0.31 microgram/l) than in untrained subjects (NA: 2.13 +/- 0.80 microgram/l; A: 0.40 +/- 0,34 microgram/l). During recovery, no significant difference was observed between the two groups.

[Determination of plasma noradrenaline by automatic high pressure liquid chromatography with electrochemical detection]. / Détermination de la noradrénaline plasmatique par chromatographie liquide haute pression en mode automatique avec détection électrochimique.

A method for the plasma noradrenaline (NA) analysis by reversed-phase liquid chromatography with electrochemical detection is described. The plasma sample preparation includes two-steps: ion-exchange and alumina adsorption. The use of a data system and an automatic sampler enables the injection of samples in series. Using this technique, determination of plasma NA concentration in 34 healthy subjects (27.4 +/- 7.2 years) gave the following results: 0.28 +/- 0.10 micrograms/l after 30 min of resting in the supine position and 0.52 +/- 0.17 micrograms/l after 5 min of upright position.