Analytical validation for a series of marker compounds used to assess renal drug elimination processes.

Renal drug elimination is determined by glomerular filtration, tubular secretion, and tubular reabsorption. Changes in the integrity of these processes influence renal drug clearance, and these changes may not be detected by conventional measures of renal function such as creatinine clearance. The aim of the current study was to examine the analytic issues needed to develop a cocktail of marker drugs (fluconazole, rac-pindolol, para-aminohippuric acid, sinistrin) to measure simultaneously the mechanisms contributing to renal clearance. High-performance liquid chromatographic methods of analysis for fluconazole, pindolol, para-aminohippuric acid, and creatinine and an enzymatic assay for sinistrin were developed or modified and then validated to allow determination of each of the compounds in both plasma and urine in the presence of all other marker drugs. A pilot clinical study in one volunteer was conducted to ensure that the assays were suitable for quantitating all the marker drugs to the sensitivity and specificity needed to allow accurate determination of individual renal clearances. The performance of all assays (plasma and urine) complied with published validation criteria. All standard curves displayed linearity over the concentration ranges required, with coefficients of correlation greater than 0.99. The precision of the interday and intraday variabilities of quality controls for each marker in plasma and urine were all less than 11.9% for each marker. Recoveries of markers (and internal standards) in plasma and urine were all at least 90%. All markers investigated were shown to be stable when plasma or urine was frozen and thawed. For all the assays developed, there were no interferences from other markers or endogenous substances. In a pilot clinical study, concentrations of all markers could be accurately and reproducibly determined for a sufficient duration of time after administration to calculate accurate renal clearance for each marker. This article presents details of the analytic techniques developed for measuring concentrations of marker drugs for different renal elimination processes administered as a single dose to define the processes contributing to renal drug elimination.

Longiberine and O-methyllongiberine, dimeric protoberberine-benzyl tetrahydroisoquinoline alkaloids from Thalictrum longistylum(1).

Two benzyltetrahydroisoquinoline-protoberberine dimers, longiberine (1) and O-methyllongiberine (2), were isolated from the roots of Thalictrum longistylum and represent a new class of dimeric alkaloids. The structure of longiberine (1) was established by spectral and chemical methods. Reductive cleavage of O-ethyllongiberine (4) with Na/liquid NH(3) yielded (+)-(S)-N-methylcoclaurine (5), which determined one-half of the dimer, and 1D and 2D NMR studies arranged the substituents on the protoberberine nucleus. Chemical conversion of thalidezine (6) to 1 via the O-acetyl N,N-didemethyl derivative 9, which was methylenated in the Mannich reaction and N-methylated by the Eschweiler-Clarke procedure, established the second asymmetric center as S and confirmed the ring size and the order of the substituents for 1. Methylation of 1 with diazomethane formed the O-methyl derivative 2, identical with the natural product.

Evaluation of an immunoassay (EMIT) for mycophenolic acid in plasma from renal transplant recipients compared with a high-performance liquid chromatography assay.

Mycophenolic acid is an immunosuppressant administered as a bioavailable ester, mycophenolate mofetil. The pharmacokinetics of mycophenolic acid have been reported to be variable. Accurate measurement of concentrations of this drug could be important to adjust doses. The aim of this study was to compare the enzyme-multiplied immunoassay technique (EMIT [Dade Behring; San Jose, CA, U.S.A.]) for mycophenolic acid with a high-performance liquid chromatographic (HPLC) assay using samples collected from renal transplant recipients. The HPLC assay used solid phase extraction and a C18 stationary phase with ultraviolet (UV) detection (254 nm). The immunoassay required no manual sample preparation. Plasma samples (n=102) from seven patients, collected at various times after a dose, were analyzed using both methods. Both assays fulfilled quality-control criteria. Higher concentrations were consistently measured in patient samples when using EMIT. The mean (+/-standard deviation [SD]) bias (EMIT-HPLC) was 1.88+/-0.86 mg/L. The differences in concentrations were higher in the middle of a dosage interval, suggesting that a metabolite might have been responsible for overestimation. Measurement of glucuronide concentrations by HPLC demonstrated only a weak correlation between assay differences and glucuronide concentrations. If the crossreacting substance is active, EMIT could provide a superior measure of immunosuppression; if inactive, further work is needed to improve antibody specificity. In conclusion, it was found that EMIT overestimates the concentration of mycophenolic acid in plasma samples from renal transplant recipients compared with HPLC analysis.

Determination of pindolol enantiomers in human plasma and urine by simple liquid-liquid extraction and high-performance liquid chromatography.

A simple method for the measurement of pindolol enantiomers by HPLC is presented. Alkalinized serum or urine is extracted with ethyl acetate and the residue remaining after evaporation of the organic layer is then derivatised with (S)-(-)-alpha-methylbenzyl isocyanate. The diastereoisomers of derivatised pindolol and metoprolol (internal standard) are separated by high-performance liquid chromatography (HPLC) using a C18 silica column and detected using fluorescence (excitation gamma: 215 nm, emission gamma: 320 nm). The assay displays reproducible linearity for pindolol enantiomers with a correlation coefficient of r2> or =0.998 over the concentration range 8-100 ng ml(-1) for plasma and 0.1-2.5 microg ml(-1) for urine. The coefficient of variation for accuracy and precision of the quality control samples for both plasma and urine are consistently <10%. Assay parameters are similar to those of previously published assays for pindolol enantiomers, however this assay is significantly easier and cheaper to run. Clinically relevant concentrations of each pindolol enantiomer can readily be measured.

[Anesthesia in surgery for malformative and degenerative cervical spine]. / Anesthésie pour chirurgie du rachis cervical malformatif et dégénératif.

Anaesthesia in patients with malformative and degenerative abnormalities of cervical spine poses a number of specific problems. A crucial point is the indispensable evaluation and observation before and during anaesthesia. Somatosensory evoked potentials being used to monitor nervous system pathways at risk during surgical procedures the effect of anaesthetic agents on these parameters are to be well known. Some pathologies are liable to per and postoperative specific risks breeding complications.

[Anesthesia for surgery of degenerative and abnormal cervical spine]. / Anesthésie pour chirurgie du rachis cervical dégénératif et malformatif.

A feature common to all congenital or inflammatory abnormalities of the cervical spine is an actual or potential reduction in the lumen of the spinal canal. The spinal cord and nerve roots are at risk. During intubation, and positioning the patient on the table, all untoward movements of the cervical spine may lead to spinal cord compression. Abnormalities of the cervical spine carry the risk of a difficult intubation. If there is much debate as to what constitutes optimum management of the airway, there is no evidence that any one method is the best. Recognizing the possible instability and intubating with care, are probably much more important in preserving neurological function than any particular mode of intubation. During maintenance of anaesthesia, the main goal is to preserve adequate spinal cord perfusion in order to prevent further damage. Spinal cord blood flow seems to be regulated by the same factors as cerebral blood flow. Hypercapnia increases cord blood flow while hypocapnia decreases it. Therefore, normocapnia or mild hypocapnia is recommended. Induced hypotension is frequently used to decrease blood loss. However, in patients with a marginally perfused spinal cord, the reduction in blood flow may cause ischaemia of the spinal cord and may therefore be relatively contraindicated. In addition to standard intraoperative monitoring, spinal cord monitoring is almost mandatory. Monitoring somatosensory evoked potentials is used routinely. However, the major limitation is that this technique only monitors dorsal column function; theoretically, motor paralysis can occur despite a lack of change in recorded signals. Neurogenic motor evoked potentials may now be used to monitor anterior spinal cord integrity.(ABSTRACT TRUNCATED AT 250 WORDS)

Intertester reliability of the hand-held dynamometer for wrist flexion and extension.

This study was conducted to determine the intertester reliability of a hand-held dynamometer for the wrist flexor and extensor muscles. Using the break test on 20 healthy subjects, three testers obtained two measures of strength for each muscle group. The data were analyzed using the Pearson product-moment correlation coefficients, intraclass correlations, and an analysis of variance (ANOVA) for repeated measures. Our Pearson product-moment correlations ranged from 0.89 to 0.95 for the intertester reliability of the wrist extensors and 0.90 to 0.93 for the wrist flexors, whereas the intraclass coefficients were 0.91 and 0.85, respectively. Although these correlations were high, ANOVA tests revealed that significant differences existed between testers for both the wrist flexion and extension data (p less than .05). From these results we concluded that although the correlations between testers were good, ANOVA tests suggested that there was limited reliability between testers.

Consequences of fluid absorption during transurethral resection of the prostate using distilled water or glycine 1.5 per cent.

This prospective and randomized study compared the consequences of two irrigating fluids, distilled water and glycine for transurethral prostatectomy. Forty-nine consecutive unselected patients undergoing transurethral resection of the prostate with spinal anaesthesia were investigated. The irrigating fluid was either distilled water (group A, 24 patients) or glycine 1.5 per cent (group B, 25 patients). The absorption of irrigating fluid was measured, all surgical events and any clinical signs of TURP syndrome during and after surgery were recorded. Early signs of TURP syndrome were observed in one patient in group A and in four in group B without further consequence. From all the biological variables, only plasma protein concentration, haematocrit, free plasma haemoglobin and free bilirubin concentrations were found to have changed. Plasma protein concentration and haematocrit decreased significantly during and after surgery in the two groups. Free plasma haemoglobin increased significantly with time: a significantly higher concentration was observed in group A than group B. Free bilirubin concentration increased with time in the two groups and was statistically greater in group A. With the two irrigating fluids, we observed a significant amount of haemolysis and haemodilution without clinical consequences. A low irrigating fluid pressure, a short resection time, and the use of spinal anaesthesia seems to us to be essential. Close observation of patients following transurethral prostatectomy is needed but the choice of the irrigating fluid does not seem to be important.

[Acute intracranial subdural hematoma of arterial origin after spinal anesthesia]. / Hématome sous-dural aigu intracrânien d'origine artérielle après rachianesthésie.

A case of an acute intracranial subdural haematoma occurring shortly after spinal anaesthesia is reported. A 67 year old poorly controlled hypertensive man, ASA II, underwent removal of a prostatic adenoma under spinal anaesthesia. He complained of postural headache on the third day after surgery. Unresponsive to the usual analgesics, his headache became severe, persistent and non postural on the fifth day. Twenty-four hours later, he suddenly presented with a left hemiplegia and became comatose. Computed axial tomography showed a large left-sided subdural haematoma, lying over the left hemisphere. During the immediate surgical removal, a pulsatile arterial bleeding originating from a small cortical artery was discovered, and stopped. The patient slowly recovered consciousness, but the hemiplegia remained. He finally died six months later of bronchopneumonia. The link between the haematoma and the spinal anaesthetic is not proven; the possible relationship between the two is discussed.

Haemodynamic effects of high plasma concentrations of bupivacaine in the dog.

The threshold concentrations responsible for circulatory collapse were experimentally investigated by intravenously infusing the drug at high rates (0.2 and 0.3 mg kg-1 min-1 over 20 min, and 0.4 mg kg-1 over 10 min) to 11 anaesthetized and ventilated dogs. Bupivacaine plasma concentrations at the time of haemodynamic measurements were, respectively, 4303 +/- 46, 5829 +/- 615, and 8930 +/- 689 ng ml-1 (means +/- SEM). Cardiac output appeared to be the first and the most affected of the haemodynamic variables studied. Its reduction was already significant with the 0.2 mg kg-1 min-1 bupivacaine infusion, whereas mean systolic blood pressure remained unchanged because of the compensatory increase in vascular resistance. The fall of cardiac output was enhanced by the rise in bupivacaine infusion rate, with simultaneous substantial decreases in left ventricular pressure and LV dP/dt max. At this stage, the increase in systemic vascular resistance was less marked than at low infusion rates, and was not sufficient to prevent hypotension. The variations of mean pulmonary blood pressure and pulmonary capillary wedge pressure did not reach statistical significance, and the absence of significant change in mean pulmonary blood pressure at the time cardiac output was reduced reflected the increase in pulmonary vascular resistance. These results suggest that high plasma concentrations of bupivacaine exert a depressant effect on cardiac contractions earlier than on arteriolar tone.

[Systemic toxicity of local anesthetics. Pharmacokinetic and pharmacodynamic factors]. / Toxicité systémique des anesthésiques locaux. Facteurs pharmacocinétiques et pharmacodynamiques.

Local anaesthetics can have systemic adverse effects, mostly affecting the central nervous system and the heart. The physicochemical characteristics of the different local anaesthetics are recalled, for they determine the relationship between structure, activity and toxicity. The pharmacokinetic factors involved in the toxic effects of local anaesthetics, whether the drug is given in a single extravascular dose or, accidentally, within a blood vessel, are discussed. The toxic effects of repeated administrations of local anaesthetics depend on the metabolism of the drug as well as on pharmacokinetic factors. Possible maximal doses and drug interactions are also discussed. The mechanism of action of local anaesthetics, which block the sodium channel, explains their tissue toxicity and, more specifically, their central nervous and cardiovascular toxicities, which are more pronounced for the more potent local anaesthetic agents (bupivacaine, etidocaine). Systemic maternal effects and transplacental passage probably explain their foetal toxicity. Specific toxic effects are seen with some drugs, such as methaemoglobinaemia and allergic reactions (rarely for amide agents). Overall, local anaesthetic accidents are rare, but they must be prevented.

Pharmacokinetics of bupivacaine after axillary brachial plexus block.

Severe cardiovascular complications have been associated with regional anesthesia using bupivacaine. Furthermore, in our practice, axillary brachial plexus block is commonly used for surgical emergencies of the hand in out-patients. The pharmacokinetics parameters: peak height (Cmax), peak time (tmax), half life of plasma elimination (t1/2), total apparent clearance (Cl), mean time of plasma retention (t) were studied in 20 male and female patients (mean age 35 and 32 years) receiving axillary local anesthesia by bupivacaine (BU) only (A group = 100 mg), B group BU = 200 mg, or BU + lidocaine (LI) (C group = BU 100 mg + LI 200 mg), plasmatic BU and LI were simultaneously measured by HPLC method. There were no significant differences in the pharmacokinetic data observed in groups A, B and C; total apparent clearances and half times of plasma elimination of BU after brachial plexus block are similar compared to those observed after i.v. administration. Absorption of BU seems to be total while the value of Cmax are very low compared to usual neurotoxic plasma levels, but near that of plasma concentrations observed in cardiac complications. All the tmax observed were under 2 h and the dose independence of the kinetic of BU is not admissible in this study. The association of LI induce no modification of the kinetic of BU. This work concludes that in this way of administration, the absorption of BU seems to be total. Pharmacokinetics of BU is dose dependent and the association of LI induces no significant modification of BU kinetics.

Electrophysiological study in the dog of the risk of cardiac toxicity of bupivacaine.

The risk of toxic effects on the heart of bupivacaine following several kinds of locoregional anaesthesia has been investigated in the dog in situ heart by determining conduction time and effective refractory period in the various parts of the conduction system and the ventricular muscle, as well as the discharge rate of the sinus node. Bupivacaine, i.v. infused at 3 rates, 0.2, 0.3 and 0.4 mg X kg-1 X min-1, proved to have depressant effects on conduction, automatism and excitability. It slows down conduction in all the parts of the myocardium, considerably at high stimulation frequencies, but always much more in the His-Purkinje system and the ventricular contractile fibres than in the atrioventricular node, because it tends to block the sodium rather than the calcium or potassium channel. Its effect remain more moderate, indeed, on sinus automatism and atrial and mainly ventricular refractoriness. Its danger lies, therefore, in the inhibition of conduction, with atrioventricular or His bundle branch block, but more frequently reentrant arrhythmias, likely to result in ventricular fibrillation. However: these alterations are observed with very high plasma levels (about 4 to 9 micrograms X ml-1), much higher than usual peak concentrations following spinal anaesthesia (0.10 micrograms X ml-1) or even epidural anaesthesia or brachial plexus block (1.20 micrograms X ml-1); reversal of these alterations occurs rapidly (reduction by 50% within 30 min for instance), when they have not led to ventricular fibrillation or they have not been associated with circulatory collapse.