Stability and in vivo behavior of Rh[16aneS4-diol]211 at complex: a potential precursor for astatine radiopharmaceuticals.

INTRODUCTION: The heavy halogen (211)At is of great interest for targeted radiotherapy because it decays by the emission of short-range, high-energy α-particles. However, many astatine compounds that have been synthesized are unstable in vivo, providing motivation for seeking other (211)At labeling strategies. One relatively unexplored approach is to utilize prosthetic groups based on astatinated rhodium (III) complex stabilized with a tetrathioether macrocyclic ligand - Rh[16aneS(4)-diol](211)At. The purpose of the current study was to evaluate the in vitro and in vivo stability of this complex in comparison to its iodine analog - Rh[16aneS(4)-diol](131)I. METHODS: Rh[16aneS(4)-diol](211)At and Rh[16aneS(4)-diol](131)I complexes were synthesized and purified by HPLC. The stability of both complexes was evaluated in vitro by incubation in phosphate-buffered saline (PBS) and human serum at different temperatures. The in vivo behavior of the two radiohalogenated complexes was assessed by a paired-label biodistribution study in normal Balb/c mice. RESULTS: Both complexes were synthesized in high yield and purity. Almost no degradation was observed for Rh[16aneS(4)-diol](131)I in PBS over a 72 h incubation. The astatinated analog exhibited good stability in PBS over 14 h. A slow decline in the percentage of intact complex was observed for both tracers in human serum. In the biodistribution study, retention of (211)At in most tissues was higher than that of (131)I at all time points, especially in spleen and lungs. Renal clearance of Rh[16aneS(4)-diol](211)At and Rh[16aneS(4)-diol](131)I predominated, with 84.1 ± 2.3% and 94.6 ± 0.9% of injected dose excreted via the urine at 4 h. CONCLUSIONS: The Rh[16aneS(4)-diol](211)At complex might be useful for constructing prosthetic groups for the astatination of biomolecules and further studies are planned to evaluate this possibility.

Synthesis and stability of oxetane analogs of thalidomide and lenalidomide.

Oxetanes are used in drug discovery to enable physicochemical and metabolic property enhancement for the structures to which they are grafted. An imide C═O to oxetane swap on thalidomide and lenalidomide templates provides analogs with similar physicochemical and in vitro properties of the parent drugs, with an important exception: oxetane analog 2 displays a clear differentiation with respect to human plasma stability. The prospect of limiting in vivo stability/metabolism, blocking in vivo racemization, and potentially altering teratogenicity is appealing.

Rapid method for the analysis of red blood cell fatty acids by reversed-phase high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for a rapid qualitative and quantitative analysis of p-bromophenacyl esters of red blood cell fatty acids in humans. Both free and bound fatty acids, extracted with hexane-2-propanol (3:2) from packed red blood cells were derivatized with p-bromophenacyl bromide and analysed. Ten identical samples taken from a mixed pool of packed red blood cells from healthy subjects were analysed on two different columns. The fatty acid p-bromophenacyl esters were analysed on a 10 RP-18 column with methanol-acetonitrile-0.01 M ammonium formate as mobile phase and also on a 10 RP-8 column with acetonitrile-0.01 M ammonium formate as mobile phase. The two methods gave analogous results except in total analysis time: that on a 10 RP-8 column is ca. 40% shorter. Furthermore, a quantitative analysis of a standard solution to evaluate the extraction procedure in the absence or in the presence of the red blood cell core indicated a significant difference when the core is present.

Biological monitoring of styrene metabolites in blood.

Ten men occupationally exposed to styrene in two glass-fiber reinforced plastics factories were studied during three consecutive workdays. The mean external exposure level was 99 mg/m3. The total pulmonary uptake of styrene was estimated from measurements of the styrene concentration in inspired air, the pulmonary ventilation, and the relative uptake. A gas chromatographic method based on electron capture detection was used to quantify styrene glycol, as well as styrene-7,8-oxide, in blood. The concentration of styrene glycol appeared to be linearly related to the preceding uptake of styrene. When the uptake during 5 h immediately before the blood sampling was considered, the correlation coefficient (r) obtained the value of 0.90. The concentration of styrene-7,8-oxide was at the detection limit of 0.02 mumol/l in most samples. A weaker correlation between the concentration of styrene in blood and the uptake during the hour immediately preceding the blood sampling was obtained (r = 0.71).

Síntesis de éteres cíclicos prostanoides con actividad hematológica o inmunológica / Synthesis of prostandid cyclic ethers with hematological or inmunological activity

En este trabajo se presenta la síntesis de algunos éteres cíclicos prostanoides, análogos de la prostaciclina obtenidos partiendo del intermediario PGA2 (extraído del coral blando Plexura homomalla, recolectado en la costa note de Venezuela); conjuntamente con algunas pruebas farmacológicas preminares en el área de inmunología o hematología

Determination of hydroxypropylhistidine in haemoglobin as a measure of exposure to propylene oxide using high resolution gas chromatography mass spectrometry.

The alkylating agent propylene oxide is a potential carcinogen. Exposure to this compound leads to the formation of N-3'-(2-hydroxypropyl)histidine in protein. A sensitive and specific method has been developed for the determination of this alkylated amino acid in rat and human haemoglobin using high resolution gas chromatography with selected ion monitoring. Globin isolated from blood was hydrolysed with 6 M HCl and the protein hydrolysate chromatographed on a Dowex 50W H+ column. The amino acids in the partially purified extract were analysed as N-heptafluorobutyryl methyl esters using an SE-52 fused silica capillary column. Quantification was made by monitoring the ion m/z 560 [M-COOCH3)+ derived from the derivatized hydroxypropylhistidine in the sample and the corresponding ion at m/z 565 from the pentadeutero analogue of the alkylated amino acid added initially to the globin as an internal standard. The method has been used to quantify hydroxypropylhistidine down to levels of 2 microgram gm-1 haemoglobin and has been applied to studies in rats exposed to propylene oxide.

Styrene oxidation to styrene oxide in human blood erythrocytes and lymphocytes.

Human erythrocytes and lymphocytes catalyzed styrene oxidation to styrene oxide. The erythrocyte catalyzed reaction was inhibited by CO, occurred in the absence of NADPH and NADH and was undetectable in the absence of O2 and with erythrocyte membranes. Lymphocyte catalyzed styrene oxide formation required the addition of cofactors and these cells showed 6 times the activity of erythrocytes with a 4 times lower styrene concentration. Although lymphocytes appear to be more active than red blood cells in styrene oxidation, their contribution to styrene metabolism in whole blood seems extremely small.

Competitive nephelometric immunoassay of carbamazepine and its epoxide metabolite in patient blood plasma.

We have prepared anti-carbamazepine antiserum and developed a competitive nephelometric immunoassay for the determination of carbamazepine and its epoxide metabolite in patient blood plasma. The antiserum was raised by immunization of a rabbit with a carbamazepine (bovine serum albumin) conjugate. A carbamazepine-(human serum albumin) conjugate was used as an assay reagent. Carbamazepine and its epoxide inhibited competitively and almost equally the immunoprecipitation of the carbamazepine-(human serum albumin) conjugate. Therefore carbamazepine and its epoxide could be determined by the measurement of the scattered light from the immunoprecipitate in assay solution on a laser nephelometer. Patient plasma specimens were analyzed, and the values correlated well to those determined by the high-performance liquid chromatography. The epoxide concentrations were considerably lower than therapeutic carbamazepine concentrations, which was certified by the chromatographic results. This immunoassay was rapid (incubation time: within 20 min), simple and precise (coefficient of variation: less than 6%), and required as little as 6 microliters of plasma, and seemed suitable for routine monitoring of carbamazepine.

Behavioral and neuropharmacological toxicology of the macrocyclic ether 18-crown-6.

18-CROWN-6 was assessed for neurologic effects in rats, mice, and rabbits by intravenous (IV) and intraperitoneal (IP) routes of administration. Male rats and mice exhibited no effects with IV doses to 20 mg/kg. Given IP doses of 20 to 160 mg/kg/day, rats and mice exhibited numerous signs, including aggression, tremors, muscle weakness and a degradation of some reflexes. All signs faded after four days when dosage levels were kept constant, but returned when the dose was doubled. All signs disappeared upon discontinuance of exposure. Treatment with PCPA (p-chlorophenylalanine) or dibenzyline caused most signs to disappear. Rabbits given 6.0 mg/kg/day IV displayed tremors, hyperactivity, unsteady gait and stereotypic behavior, with acclimation as in rats and mice. 18-CROWN-6 had no activity in isolated tissue preparations unless it was first incubated with tissues. PCPA and dibenzyline reversibly blocked the actions of incubated 18-CROWN-6 on isolated tissue. 18-CROWN-6 is hypothesized to be metabolized to a serotonergic agonist.

Measurement of carbamazepine and its epoxide metabolite by high-performance liquid chromatography, and a comparison of assay techniques for the analysis of carbamazepine.

We describe a modified high-performance liquid-chromatographic method for the simultaneous analysis of carbamazepine andits biologically active metabolite, carbamazepine-10, 11-epoxide. Concentrations of both these compounds in the plasma of 35 epileptic patients receiving chronic carbamazepine therapy are presented. Concentrations of carbamazepine in plasma were related to those of carbamazepine-10, 11-epoxide (r - 0.495, P less than 0.05). Total daily doses of carbamazepine were better correlated with plasma concentrations of carbamazepine-10, 11-epoxide (r = 0.714, P less than 0.001) than of carbamazepine (r = 0.269, P greater than 0.05). Close correlations were found between results of the three assay procedures we used to measure plasma carbamazepine concentrations: high-performance liquid chromatography, gas-liquid chromatography, and enzyme immunoassay. Correlation coefficients exceeded 0.97 and regression slopes were near unity, indicating that all three procedures were individually specific for the quantification of plasma carbamazepine.

High-performance liquid chromatographic analysis of dianhydrogalactitol in plasma by derivatization with sodium diethyldithiocarbamate.

A high-performance liquid chromatographic method is described for measuring submicrogram quantities of dianhydrogalactitol, a promising anti-neoplastic agent, in plasma. The drug is derivatized directly in plasma with sodium diethyldithiocarbamate to form a bis(dithiocarbamoyl) ester which absorbs UV light at 254 nm (am 17,000). The derivatized product is then extracted quantitatively into chloroform and separated by normal phase chromatography (muBondpak CN column). Dianhydrogalactitol concentration below 50 ng/ml of plasma can be detected in the eluent.

Carbamazepine and its 10,11-epoxide in children and adults with epilepsy.

The plasma concentrations of carbamazepine and its 10,11-epoxide were measured in 37 children and 13 adults with epilepsy during maintenance therapy. The children formed relatively more of the epoxy metabolite than adults. The daily dose, expressed as mg/kg or mg/m2, showed a statistically significant correlation with blood level in children, but not in adults. The cerebrospinal fluid concentrations of carbamazepine and carbamazepine-10,11-epoxide in nine children were 33 and 41 per cent, respectively, of the concomitant plasma level.

Gas-chromatographic analysis for 1,2:5,6-dianhydrogalactitol, an anti-neoplastic agent, in plasma.

We describe a gas chromatographic method for measuring submicrogram quantities of dianhydrogalactitol, a promising antineoplastic agent (currently undergoing clinical trials in humans), in plasma. The drug is first extracted from blood plasma by saturating the aqueous phase with solid potassium carbonate and extracting with isopropanol/chloroform (9/1 by vol). It is then converted to the corresponding n-butaneboronic ester by reaction at room temperature with butaneboronic acid and chromatographed on an SE-30 (3%) column, with flame ionization detection. Practicality of the method for monitoring drug distribution was demonstrated by administering dianhydrogalactitol in therapeutic doses to a dog and monitoring its concentrations in blood for the next 2 h.

Determination of carbamazepine and its epoxide metabolite in plasma by high-speed liquid chromatography.

A liquid-chromatographic method for the simultaneous determination of carbamazepine and its active metabolite (carbamazepine 10,11-epoxide) in plasma has been developed. The two compounds were identified in plasma by mass spectrometry. The lower limit of sensitivity is about 4 and 40 ng for the drug and its metabolite, respectively. 10,11-Dihydrocarbamazepine is used as internal standard for the determinations, which have precisions of 2.2 and 4.2%, respectively. No derivatization is needed. The specificity of the method for carbamazepine is shown by the significant correlation (r = 0.99) between the results obtained by this method and by mass fragmentography for the drug in plasma of patients.