Barbiturates characteristics

In rabbits under light amytal anesthesia, chlordan has no direcr effect on the blood pressure, but produces a type of respiration having many characteristics in common with Cheyne-Stokes type. The generalized tremors, opisthotonus, tonic and clonic convulsions, produced by chlordan were decreased or abolished and respiration restored to normal by suitable injections of the sodium salts of amytal, phenobarbital, and pentothal. The LD60 of chlordan, which was about 20 mg. per kg. on intravenous administration to intact rabbits, was increased to about 60 mg. per kg. through the antidotal action of the barbiturates. An unidentified chlorine-containing degradation product with acidic properties was recovered from the urine of rabbits treated with chlordan. Approximately one third of its chlorine content was set free on hydrolysis at 100° C. with sodium hydroxide in either absolute alcohol or in water. 

These dyes are invariably monoazo compounds with the reactive system attached to the diazo component, owing to the ready availability of monosulphonated phenylenediamine intermediates. Pyrazolone couplers are most commonly used, as in structure 7.82 (where Z is the reactive grouping), and this is particularly the case for greenish yellow vinylsulphone dyes. Catalytic wet fading by phthalocyanine or triphenodioxazine blues is a characteristic weakness of azopyrazolone yellows (section 3.3.4). Pyridones (7.83), barbituric acid (7.84) and acetoacetarylide (7.85 Ar = aryl) coupling components are also represented in this sector, with the same type of diazo component to carry the reactive function. 

Due to their narrower margin of safety (risk of misuse for suicide) and their potential to produce physical dependence, barbiturates are no longer or only rarely used as hypnotics. Dependence on them has all the characteristics of an addiction (p. 210). 

Elemental composition H 3.73%, C 44.44%, N 51.83%. HCN may be analyzed by GC or GC/MS. The aqueous solution may be directly injected onto the GC column and determined by an FID. For GC/MS determination, an alcoholic solution may be injected into the column. The characteristic mass ions are 27 and 26. The cyanide ion in aqueous solution also may be measured by cyanide ion-selective electrode, titrimetry, and by colorimetric methods (APHA, AWWA, WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). For colorimetric analysis, the aqueous solution may be treated with a dilute caustic soda solution, followed by treatment with chloramine-T, and then with pyridine-barbituric acid reagent. A red-blue color develops, the absorbance of which is measured by spectrophotometer at 578 nm. The concentration of CN is determined from a standard cahbration curve using KCN standards. 

Benzodiazepines, barbiturates, and most older sedative-hypnotic drugs exert calming effects with concomitant reduction of anxiety at relatively low doses. In most cases, however, the anxiolytic actions of sedative-hypnotics are accompanied by some depressant effects on psychomotor and cognitive functions. In experimental animal models, benzodiazepines and older sedative-hypnotic drugs are able to disinhibit punishment-suppressed behavior. This disinhibition has been equated with antianxiety effects of sedative-hypnotics, and it is not a characteristic of all drugs that have sedative effects, eg, the... 

Induction of the microsomal enzymes may also have other effects as well as the increased production of particular enzymes and isozymes. Here again the different types of inducer vary. Thus, the barbiturate type of inducer differs significantly from the polycyclic hydrocarbon type as can be seen from the list below. Some of the characteristic changes caused by the barbiturate type of inducer are... 

On the other hand, Mori64 could not obtain any precipitate of the 2-fural-dehyde-barbituric acid complex, characteristic of pentose, from 5 g. of the purified barium salt of the mucilage, whereas he obtained it from an unpurified specimen. From this he concluded that pentose should be recognized as an impurity in the mucilage. Johnston and Percival88 identified 2,3,4-trimethyl-D-xylose in the hydrolyzed products of car-rageenin but they have stated that it may have been derived from a contaminating xylan. These views find support in that pentose was not... 

Tolerance to many of the effects of barbiturates develops rapidly, but it is a characteristic of this class of drugs that tolerance to the effects does not develop uniformly. Tolerance builds to the euphoric effects but not to the lethal dose euphoric doses come closer and closer to the lethal dose. 

A. H. Stead, R. Gill, A. T. Evans, and A. C. Moffat, Prediction of gas chromatographic retention characteristics of barbiturates from molecular structure, J. Chromatogr., 234 211 (1982). 

The utility of the highly soluble 6-cyclodextrin derivatives (soluble polymer and dimethyl-6-cyclodextrin) in RPTLC is illustrated in the separation of barbiturates. The lipophilicity of a barbiturate or any guest decreases when included in a cyclodextrin-cavity. Therefore its mobility is modified in reversed phase thin layer chromatography. With this simple and rapid method, the stability of a complex can be estimated empirically (Table II). The "b" value of the following equation is characteristic for the complex stability (in water ethanol =4 1 solution, R determined at 5 different cyclodextrin concentrations for 21 barbiturates) ... 

Hydrogen-bonding metrics and patterns are characteristic properties of molecules. It is by no means certain that a )NH 0=C bond will have exactly the same metrical properties when it occurs in a peptide, a barbiturate, and a nucleoside. In fact, as will be shown later, there are small, but significant, differences in these metrical properties. There are also differences in the pattern characteristics. The patterns that are observed in the crystal structures of these various types of small biological molecules provide a portfolio of observed hydrogen bond structures. These can be used as models for interpretations of structure and for hypotheses concerning intermolecular interactions in those situations where direct observation of the position of the hydrogen atom is experimentally impossible. 

Usually the H NMR spectra of the aggregates (135)3-(136)6 are simple, exhibiting for instance only two sharp singlets for the imide protons of the barbiturate (at 13-14 ppm in CDC13). This strong downfield shift is characteristic for the melamine-barbiturate hexamer, while the simple pattern in general is only in agreement with the formation of the chiral assembly with an overall D3 symmetry. However, the simultaneous formation of all three supramolecular diastereomers was detected by H NMR spectroscopy in the case of sterically hindered cyanurates... 

Chemical derivatives may be used to improve the chromatographic characteristics of polar compounds, e.g. acids may be converted to their methyl esters and barbiturates to their methyl derivatives. This technique may also provide information concerning the number of active sites in a molecule by noting the increase in molecular weight on methylation. In many cases the mass spectrum of tiie derivative may be of more use for identification purposes. 

An example of the use of NMR in forensic science is the identification of four 5-ethyl-5-alkyl substituted barbiturates, butobarbitone, pentobarbitone, secbutobarbitone, and amylobarbitone. The proton spectra of all four barbiturates show a very broad signal at around 5 8 ppm to 5 10 ppm which is characteristic of amido protons. The useful region of the spectrum for the differentiation of these barbiturates lies between 5... 

This is needed because of the mode of separation, with reversed-phase HPLC being based on a partitioning process. As the lipophilicity of the side-chain at the C5 position increases, so the barbiturate compound will partition preferentially into the stationary phase, but not re-enter the mobile phase. Increasing the proportion of acetonitrile in the solvent system will result in better mass transfer characteristics, and hence improved chromatography, for these more lipophilic barbiturates. 

Suzuki, H. Kneller, M. B. Rock, D. A. Jones, J. P. Trager, W. F. Rettie, A. E. Active-site characteristics of CYP2C19 and CYP2C9 probed with hydantoin and barbiturate inhibitors. Arch Biochem Biophys. 2004, 429 (1), 1-15. 

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