A brief technical communication: detection of fentanyl in urine

A reliable and sensitive method to analyze fentanyl in urine was developed using radioimmunoassay (RIA). Fentanyl, a highly lipophilic drug (pKa 7.7), has become a common drug of abuse. We evaluated three analytical techniques to detect fentanyl in urine. This paper reports the best of the three - a modified solvent extraction combined with a fentanyl RIA.

Influence of gestational age on pharmacokinetics of alfentanil in neonates

Alfentanil's small volume of distribution and short elimination half-life, coupled with its preservation of hemodynamic stability, make it a potentially useful drug for analgesia and anesthesia in neonates. The pharmacokinetics of alfentanil were studied in 5 infants born at 26-35 weeks' gestation and in 5 infants of greater than 36 weeks. All infants were studied in the first 3 days of life. After injection of 25 micrograms/kg alfentanil, there was no significant change in blood pressure or heart rate. No significant difference was observed in volume of distribution (0.84 +/- 0.48 l/kg vs. 0.82 +/- 0.30 l/kg), clearance (1.35 +/- 0.69 ml.kg-1.min-1 vs. 1.7 +/- 0.47 ml.kg-1.min-1), or effective half-life (455 +/- 111 min vs. 328 +/- 48 min) between the two groups. The pharmacokinetic values reported here for both preterm and full-term infants are significantly different from data reported for older children.

Microbial models of mammalian metabolism: stereoselective metabolism of warfarin in the fungus Cunninghamella elegans

Biotransformation stereoselectivity of warfarin was studied in the fungus Cunninghamella elegans (ATCC 36112) as a model of mammalian metabolism. This organism was previously shown to produce all known phenolic mammalian metabolites of warfarin, including 6-, 7-, 8-, and 4'-hydroxywarfarin, and the previously unreported 3'-hydroxywarfarin, as well as the diastereomeric warfarin alcohols, warfarin diketone, and aliphatic hydroxywarfarins. Using S-warfarin and R-warfarin as substrates, and an HPLC assay with fluorescence detection to analyze metabolite profiles, the biotransformation of warfarin was found to be highly substrate and product stereoselective. Both aromatic hydroxylation and ketone reduction were found to be stereoselective for R-warfarin. Ketone reduction with the warfarin enantiomers exhibited a high level of product stereoselectivity in that R-warfarin was predominantly reduced to its S-alcohol, while S-warfarin was reduced primarily to the corresponding R-alcohol.

Interaction of amiodarone and its analogs with calmodulin

Benzofurans have important actions on the electrical properties of myocardium; the biochemical basis of those actions is not known. Crystallographic examination of these compounds has revealed that benzofurans share structural homologies with the traditional calmodulin antagonists N-(6-aminohexyl)-5-chloro-1-naphthalene and trifluoperazine. In the present study, the ability of amiodarone, desethylamiodarone, and benziodarone to displace the fluorescent ligand 8-anilino-1-naphthalene sulfonic acid (ANS) from calmodulin, to modulate the fluorescence emission of dansylcalmodulin, and to inhibit the activation by calmodulin of bovine brain cyclic nucleotide phosphodiesterase and human erythrocyte membrane Ca2+-ATPase were investigated at concentrations ranging from 10(-8) to 10(-6) M. These benzofurans displaced ANS from calmodulin with nearly equal efficiency upon forming a 1:1 complex with that protein. Each of these compounds also produced a decreased fluorescence emission of dansylcalmodulin, but with relative efficiencies being desethylamiodarone greater than amiodarone greater than benziodarone. Amiodarone and desethylamiodarone inhibited calmodulin-stimulable phosphodiesterase activity with similar potencies. Amiodarone and benziodarone inhibited calmodulin-stimulable Ca2+-ATPase activity equally, but desethylamiodarone had no effect. The observed differential effects of the amiodarone analogs suggest that calmodulin may possess multiple benzofuran-binding sites that are recognized by specific targets and ligands of this Ca2+-binding protein and that the cellular action of amiodarone and its analogs may reflect calmodulin antagonism.

Furosemide and cerebrospinal fluid ions during acute respiratory acidosis

The purpose of this study was to investigate the effects of furosemide, an inhibitor of NaCl cotransport, on cisternal cerebrospinal fluid (CSF) acid-base balance during acute respiratory acidosis (ARA). We measured blood and CSF acid-base variables in two groups (n = 7 in each) of anesthetized, paralyzed, and mechanically ventilated dogs with bilateral ligation of renal pedicles (to eliminate saluresis). After base-line samples were obtained (-1 h), furosemide (50 mg/kg) was administered intravenously within 15 min (group II); group I received an equal volume of half-normal saline. ARA was induced 1 h later (0 h) and arterial CO2 tension was maintained between 55 and 60 Torr for 5 h. Mean cisternal CSF PCO2 was 42.8 +/- 2.6 and 39.5 +/- 1.7 Torr, respectively in groups I and II and rose approximately 20 Torr during ARA. In group I, CSF [HCO3-] was 22.0 +/- 1.0, 24.8 +/- 0.6, and 25.4 +/- 1.6 meq/l, respectively at 0, 2.5, and 5 h. Respective values for group II were 22.2 +/- 1.3, 24.3 +/- 1.8, and 24.6 +/- 1.0 meq/l. These values were not significantly different from each other. In each group, CSF [Na+-Cl-] increased significantly during ARA, but the changes were not significantly different when the two groups were compared. We conclude that furosemide at the dose used in the present study does not change ionic composition and acid-base balance of cisternal CSF compared with control. Because changes in CSF [Na+-Cl-] during ARA were similar in both groups, any inhibition of Cl- influx into CSF by furosemide should have been proportional to that of Na+.

Analysis of warfarin and its metabolites by reversed-phase ion-pair liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method was developed for the determination of warfarin and its metabolites (diastereomeric warfarin alcohols and 6-, 7-, 8-, 4'- and 3'-hydroxywarfarin) in microbial cultures. Ion-pair chromatography with tetrabutylammonium ion as the counter ion allowed for the complete resolution of all compounds at pH 7.5 on a reversed-phase (C18) column, thus permitting direct fluorescence detection without the use of post-column pH switching techniques. Analysis of cell suspension cultures of the fungus Cunninghamella elegans (ATCC 36112) indicated that this organism metabolizes warfarin to all known mammalian metabolites, plus the previously unreported 3'-hydroxywarfarin. Detection limits for all compounds were in the low nanogram range.

Effects of cholestatic hepatic disease and chronic renal failure on alfentanil pharmacokinetics in children

The role of the liver and the kidney in alfentanil metabolism has not been defined. The effects of cholestatic hepatic disease and chronic renal failure on the pharmacokinetics of alfentanil were evaluated in 9 children undergoing liver transplantation and 10 children undergoing kidney transplantation. These findings were compared with data from 10 children with normal hepatic and renal function undergoing other surgical procedures. There was no statistical difference among the 3 groups with respect to apparent volume of distribution, half-life, or clearance. In a subgroup of 3 patients undergoing liver transplantation alfentanil kinetics were determined both before and after the allograft was incorporated into the recipient's circulation. Though both volume of distribution and elimination half-life increased in the posttransplantation period, only the decrease in clearance was statistically significant. Thus, it appears that alfentanil may be a useful anesthetic agent in pediatric patients with cholestatic hepatic disease or chronic renal failure. The dose of alfentanil in these patients need not be altered except in the period immediately after liver transplantation.

Stimulation in vitro of rabbit erythrocyte cytosol phospholipid-dependent protein kinase activity. A novel action of thyroid hormone

L-Thyroxine (T4) and 3,3',5-L-triiodothyronine (T3) at 10(-10) M stimulated phospholipid- and Ca2+-dependent protein kinase activity in rabbit red cell cytosol in vitro by 151 and 176%, respectively. Kinase of 30-fold greater specific activity, developed with 0.4 mM NaCl from cytosol applied to DEAE-cellulose, was also stimulated up to 2-fold by thyroid hormone. Hormone enhancement of kinase activity occurred after 60 min of incubation at 37 degrees C prior to enzyme assay. Thyroid hormone analogues triiodothyroacetic acid, 3,5-dimethyl-3'-isopropyl-L-thyronine, D-T3, D-T4, and 3,3',5'-L-triiodothyronine (reverse T3) were inactive. These results support a role for thyroid hormone endogenously in regulation of phospholipid-dependent protein kinase activity.

Microbial models of mammalian metabolism: conversion of warfarin to 4'-hydroxywarfarin using Cunninghamella bainieri

Warfarin, an anticoagulant and "metabolic probe" for cytochrome P-450 isozyme multiplicity, is metabolized to 4'-hydroxywarfarin, a principle mammalian metabolite, using the fungus Cunninghamella bainieri (UI-3065). The metabolite was isolated from cell suspension cultures and characterized by analytical (TLC, HPLC, GC-MS) and spectral (HRMS, EI-MS, PMR) comparisons with authentic 4'-hydroxywarfarin. The mechanism of aromatic hydroxylation was examined in C. bainieri using 4'-deuterowarfarin. The absence of a primary isotope effect (KH/KD = 1.13), migration and retention of deuterium in the phenolic product [80% migration and retention (M&R)], and inhibition of the hydroxylation by carbon monoxide (93% inhibition in a 50:50 CO:O2 atmosphere) are consistent with a cytochrome P-450-mediated hydroxylation involving the classic NIH shift (arene oxide) pathway.

Enzyme replacement therapy in fibroblasts from a patient with cholesteryl ester storage disease

Enzyme replacement has long been considered only a remote possibility in the treatment of a wide range of genetic disorders, many manifested as lysosomal storage diseases. The complexity of having a particular enzyme gain access to the lysosomal compartment in a specific cell seemed insurmountable. We report here on an attempt to introduce the enzyme cholesteryl esterase into fibroblasts from a patient with cholesteryl ester storage disease (CESD). The enzyme gains access to the lysosomal compartment and the accumulating cholesteryl ester by virtue of being carried into the cell conjugated to a ligand (insulin or apoprotein B [apoB]) that binds to its own specific receptor and is internalized by the well-described process of receptor-mediated endocytosis. Regardless of whether the enzyme enters the cell via the insulin receptor or via the low-density lipoprotein (ApoB) receptor, it can be found associated with a lysosomal fraction and is effective in lowering levels of accumulated substrate, cholesteryl ester. The time course of the substrate degradation and the dependence on the receptor density and receptor density and receptor-ligand interaction indicate that the enzyme is simply being carried to the site of substrate accumulation by virtue of the fact that that is the destination of the ligand (along with its conjugated enzyme) following internalization.

Retinoic acid is a modulator of thyroid hormone activation of Ca2+-ATPase in the human erythrocyte membrane

The thyroid hormones thyroxine (T4) and 3,3',5-L-triiodothyronine (T3) stimulate plasma membrane Ca2+-ATPase (EC 3.6.1.3) activity in human erythrocytes by a mechanism independent of the cell nucleus. The current studies were conducted to determine the effect of retinoic acid on the extranuclear activation by T4 and T3 of Ca2+-ATPase in the human red cell. The retinoid inhibited basal and T4-stimulatable activity of that enzyme in a dose-dependent manner. At the highest tested concentration (10(-6) M), retinoic acid inhibited basal enzyme activity by 25% and T4-stimulated activity by 72%. A concentration as low as 5 x 10(-10) M retinoic acid shifted the dose-response curve of both T4 and T3 so that the concentration of each associated with maximal enzyme stimulation was 10(-9) M instead of 10(-10) M. Retinoic acid displaced [125I]T4 binding to red cell membranes as effectively as unlabeled T4. Retinol failed to influence either basal or T4-stimulated enzyme activity or to displace T4 binding. These results indicate that retinoic acid can partially block the T4 and T3 stimulation of Ca2+-ATPase in human red cell membranes and suggest a physiologic role for the retinoid as a modulator of this peripheral action of thyroid hormone. They suggest that the red cell membrane is an important site of action for this active retinoid.

Thyroid hormone regulation of membrane Ca2(+)-ATPase activity

The Ca2(+)-ATPase of plasma membranes from a variety of tissues is subject to stimulation in vitro, and apparently in vivo, by physiological concentrations of iodothyronines regarded as biologically active in other bioassay systems. This calmodulin-dependent action of thyroid hormone is nongenomic, that is, directly on the cell membrane and independent of the cell nucleus. In the case of human erythrocyte Ca2(+)-ATPase, this assay of thyroid hormone bioactivity is attractive as an in vitro, readily-studied model of hormone action in a human cell. Enzyme activity is paralleled, as expected, by changes in calcium pump activity. Thyroid hormone action in this system is subject to modulation by glucose and by a variety of compounds which, like iodothyronines, are hydrophobic. The mechanism of thyroid hormone action on membrane Ca2(+)-ATPase involves, at least in part, membrane lipids, including components of the phosphatidylinositol cycle. The physiologic role of thyroid hormone action on cell membrane Ca2(+)-ATPase is speculative. In plasma membranes of nonexcitable and excitable tissues, ambient thyroid hormone may set basal activity of Ca2(+)-ATPase or magnitude of the enzymatic response to calmodulin Ca2+.

A method to increase recovery of fentanyl from urine

Fentanyl, a highly lipophilic drug (pk(a) 7.7), is a common drug of abuse. The current standard techniques to detect fentanyl in urine have low recovery rates and poor sensitivity. We report a modified solvent extraction technique that can recover between 63 and 86% of the drug with a detection limit of 0.2 ng/10 ml of urine. In addition, we report the duration of urinary fentanyl excretion in 11 adolescent patients administered either low (less than 10 mg/kg) or high (20-40 mg/kg) doses of fentanyl as part of anesthesia. The mean duration of urinary fentanyl excretion was similar in the two groups, with duration ranging from 1 to 5 days, and urine fentanyl concentration ranging from 0.1 ng to 10.3 ng/10 ml of urine.

Pharmacokinetics of alfentanil in newborn premature infants and older children

Because developmental pharmacokinetics appear to be closely associated with anatomic and physiologic changes that occur with growth, we were interested in determining the disposition and elimination of alfentanil in premature infants and older children. The pharmacokinetic profile of alfentanil was determined in 6 premature infants requiring sedation for medical management or analgesia for stressful intensive-care procedures. These pharmacokinetic profiles were compared with pharmacokinetic profiles determined in 9 older infants and children undergoing operative procedures that required invasive monitoring. In both groups the plasma decay curves best fit a 2-compartment model. Compared with older children, premature infants demonstrated a significantly larger apparent volume of distribution (1.0 +/- 0.39 vs. 0.48 +/- 0.19 l/kg), a smaller clearance (2.2 +/- 2.4 vs. 5.6 +/- 2.4 ml/kg/min) and a markedly prolonged elimination half-life (525 +/- 305 vs. 60 +/- 11 min).

Microbial models of mammalian metabolism: production of novel alpha-diketone metabolites of warfarin and phenprocoumon using Aspergillus niger

1. The coumarin anticoagulants warfarin and phenprocoumon were metabolized by Aspergillus niger via oxidative ring cleavage to yield the corresponding alpha-diketone metabolites. 2. Structural identification was based upon physical, spectral, and chromatographic comparisons of isolated metabolites and synthetic standards generated by the oxidative cleavage of warfarin or phenprocoumon with pyridinium chlorochromate. 3. This pathway of metabolism has been previously observed for coumarin anticoagulants in mammalian systems.

Analogue-specific action in vitro of atrial natriuretic factor on human red blood cell Ca2+-ATPase activity

Specific atrial natriuretic factor (ANF) analogues have been found to have inhibitory activity in vitro in a calmodulin-dependent, human red blood cell membrane Ca2+-adenosine triphosphatase (ATPase) model. Studied at 10(-8) to 10(-6) M concentrations, atriopeptin I (residues 127-147 of rat prepro-ANF sequence) and atriopeptin III (residues 127-150) progressively inhibited Ca2+-ATPase activity by up to 20% (p less than 0.001). This degree of inhibition was consistent with activities of other (calmodulin-independent) enzyme inhibitors in this model. Therefore, the C-terminal Phe-Arg-Tyr sequence (residues 148-150) is unnecessary for atriopeptin action on Ca2+-ATPase. Human and rat atrial peptides with amino acids 123-150 were inactive, indicating that the 123-126 sequence (Ser-Leu-Arg-Arg) must be cleaved to activate atriopeptins in this system. Human ANF fragment 129-150 also had no effect on Ca2+-ATPase, defining the importance of residues 127-128 (Ser-Ser) proximal to the disulfide bridge (joining 129 to 145). The addition of purified calmodulin to red blood cell membranes in the presence of inhibitory ANF did not restore Ca2+-ATPase activity to normal levels, indicating that the ANF effect on this enzyme is calmodulin-independent. Atriopeptin I and atriopeptin III had no effect on red blood cell Na+, K+-ATPase activity in vitro. Thus, the structure-activity relationships of ANF analogues in this novel human cell membrane model are highly specific. Although the inhibitory action of ANF analogues on Ca2+-ATPase, a calcium pump-associated enzyme, may be unique to the red blood cell, the calcium dependence of the gluconeogenic effects of ANF in the kidney would be supported by inhibition of this ATPase.

Abnormal response to calmodulin in vitro of dystrophic chicken muscle membrane Ca2+-ATPase activity

A skeletal muscle membrane fraction enriched in sarcoplasmic reticulum (SR) contained Ca2+-ATPase activity which was stimulated in vitro in normal chickens (line 412) by 6 nM purified bovine calmodulin (33% increase over control, P less than 0.001). In contrast, striated muscle from chickens (line 413) affected with an inherited form of muscular dystrophy, but otherwise genetically similar to line 412, contained SR-enriched Ca2+-ATPase activity which was resistant to stimulation in vitro by calmodulin. Basal levels of Ca2+-ATPase activity (no added calmodulin) were comparable in muscles of unaffected and affected animals, and the Ca2+ optima of the enzymes in normal and dystrophic muscle were identical. Purified SR vesicles, obtained by calcium phosphate loading and sucrose density gradient centrifugation, showed the same resistance of dystrophic Ca2+-ATPase to exogenous calmodulin as the SR-enriched muscle membrane fraction. Dystrophic muscle had increased Ca2+ content compared to that of normal animals (P less than 0.04) and has been previously shown to contain increased levels of immuno- and bioactive calmodulin and of calmodulin mRNA. The calmodulin resistance of the Ca2+-ATPase in dystrophic muscle reflects a defect in regulation of cell Ca2+ metabolism associated with elevated cellular Ca2+ and calmodulin concentrations.

Microbiologically Catalyzed Enantio- and Diastereoselective Oxidation of Chrysanthemol Stereoisomers to Chrysanthemic Acids

The diastereo- and enantioselective microbial oxidation of a mixture of racemic cis/trans -chrysanthemols to the corresponding stereoisomeric chrysanthemic acids by Aspergillus species is described. Of the three microorganisms which were found capable of oxidizing racemic cis/trans -chrysanthemols, A. ochraceus ATCC 18500 showed complete enantioselectivity for (+)-stereoisomers [(+)- trans -chrysanthemol and (+)- cis -chrysanthemol), whereas A. flavipes ATCC 1030 and ATCC 11013 showed complete enantioselectivity for the (+)- cis -chrysanthemol but a time-dependent enantioselectivity during oxidation of trans -chrysanthemol [oxidation of (+)- trans -chrysanthemol prior to (−)- trans -chrysanthemol]. The diastereoselectivity of all three microorganisms was time dependent, in that the trans -stereoisomers were oxidized prior to the cis -isomers.

Amino acids within hypervariable region 1 of avian coronavirus IBV (Massachusetts serotype) spike glycoprotein are associated with neutralization epitopes

The spike glycoprotein (S) gene of IBV codes for a precursor protein which is cleaved into the N-terminal S1 and C-terminal S2 glycopolypeptides. The S1 glycopolypeptide, which induces neutralizing antibody, comprises approximately 520 amino acid residues. We have determined the nucleotide sequence of S1 of seven strains of the Massachusetts (Mass) serotype and the first 337 bases of two additional Mass strains. Despite the fact that the strains had been isolated over three decades in Europe and the U.S.A. there was only 4% base and 6% amino acid variation within the group. Nearly one third of the 32 amino acid differences in S1 were in two hypervariable regions (HVRs 1 and 2) comprising residues 38-51 and 99-115, identified by Niesters et al. (1986), showing that HVRs 1 and 2 are a feature of the Mass serotype. Amino acid variation within HVRs 1 and 2 was 29% and 40% respectively. Five vaccine strains could be distinguished from each other by sequencing of the first 337 nucleotides. Variants of M41 which resisted neutralization by two monoclonal antibodies (A13 and A38) had the same, single base change at position 134, resulting in substitution of proline residue 45 by histidine. This indicates that residues within HVR 1 are associated with epitopes which induce neutralizing antibody.

Calcium channel blocker inhibition of the calmodulin-dependent effects of thyroid hormone and milrinone on rabbit myocardial membrane Ca2+-ATPase activity

The Ca2+-ATPase activity of rabbit myocardial membranes is stimulated in vitro by L-thyroxine and by milrinone, a bipyridine. These effects are concentration dependent and calmodulin requiring. The calcium channel blockers nifedipine and verapamil have been reported to have anti-calmodulin effects in other assay systems. In this study we have examined the effects of nifedipine and verapamil on rabbit myocardial membrane Ca2+-ATPase activity, in the absence (basal activity) and presence of exogenous L-thyroxine (T4), 10(-10) M, and milrinone, 10(-7) M. Basal enzyme activity was inhibited by a minimum of 10(-6) M nifedipine (IC50 of 3.4 X 10(-5) M) and 10(-5) M verapamil (IC50 of 1.5 X 10(-4) M). Both calcium antagonists inhibited enzyme stimulation by T4 and milrinone, with half-maximal inhibition of T4 and milrinone effects, respectively, at 2.9 X 10(-5) M and 9.0 X 10(-6) M nifedipine and 3.0 X 10(-5) M and 5.2 X 10(-5) M verapamil. The addition of exogenous purified calmodulin, 40 ng/micrograms membrane protein, in the presence of 10(-5) M nifedipine or verapamil restored T4-stimulated enzyme activity. Nifedipine and verapamil, each at a concentration of 10(-6) M, significantly inhibited binding of radioiodinated calmodulin to rabbit heart membranes in vitro. These studies provide evidence that nifedipine and verapamil have an anti-calmodulin effect in this myocardial enzyme system. Through interaction with calmodulin, the channel blockers inhibit thyroid hormone and milrinone stimulation of myocardial membrane Ca2+-ATPase.

Clinical pharmacology of doxacurium chloride (BW A938U) in children

The neuromuscular effects of doxacurium were studied in 26 children during halothane-nitrous oxide-oxygen anesthesia. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate the cumulative dose-response relation, nine patients received incremental doses of doxacurium (2.5-10 micrograms/kg); nine patients received 27.5 micrograms/kg (the estimated ED95); eight patients received 50 micrograms/kg (1.8 X ED95). The ED25, ED50, ED75, and ED95 (estimated from linear regression plots of log dose vs probit of effect) were 11.5, 14.8, 19.0, and 27.3 micrograms/kg, respectively. Clinical duration (T25) was 27.8 +/- 10.3 (mean +/- SD) minutes at 1 X ED95 and 50.6 +/- 15.6 minutes at 1.8 X ED95. Time to recovery of the train-of-four ratio to 0.75 was 63.1 +/- 32.9 minutes at 1 X ED95 and 108.5 +/- 25.7 minutes at 1.8 X ED95. There were no significant changes in heart rate or mean arterial pressure after bolus administration of any dose of doxacurium.