Determination of colterol in human plasma and urine by reversed-phase chromatography with amperometric detection

Identification of Buctopamine and Mebuctopamine, a β2 Receptor Agonist and Its Metabolite, in Swine Hair and Feed Additives

4-[2-(t-Butylamino)-1-hydroxyethyl]phenol (buctopamine, 4), a new β₂ receptor agonist (β₂-agonist), was found to be an adulterant in feed additives for swine in Taiwan, where using β₂-agonists in food-production animals is prohibited. Buctopamine and its metabolite, 4-[2-(t-butylamino)-1-hydroxyethyl]-2-methoxyphenol (mebuctopamine, 2), were detected in swine hair specimens. Authentic compounds 2 and 4 were synthesized with 98.6% and 97.7% purity, respectively, as reference standards for analysis, and both compounds were more hydrophilic than ractopamine and clenbuterol. In a preliminary pharmacological evaluation, compounds 2 and 4 exhibited moderate human β₂ receptor binding affinity and did not show significant affinities for the human α₁, α₂, β₁, and β₃ receptors. After addition of compounds 2-4 into the β₂-agonist library, a multiresidue analysis of 26 β₂-agonists by using triple quadrupole LC/MS/MS for routine screening conducted by regulatory authorities was established, in which the common limits of quantification for the 26 β₂-agonists in swine feed and hair are 10 and 25 ng/g, respectively. In addition, the illegal use of buctopamine (4) has been effectively prevented. The results of this study are also useful for controlling the illegal use of new β₂-agonists in food-production animals.

High-performance liquid chromatographic determination of pholedrine in human serum using ion-pair extraction and amperometric detection

The method for the quantitation of pholedrine in human serum involves extraction of the sample with benzene utilizing an ion-pairing reagent, bis(2-ethylhexyl)phosphoric acid, and re-extraction into diluted phosphoric acid. Analysis is carried out on a ODS reversed-phase column with heptanesulfonate as the ion-pairing reagent. The procedure allows quantitation at the lower nanogram level and is useful for pharmacokinetic investigations.

Determination of clenbuterol in bovine plasma and tissues by gas chromatography-negative-ion chemical ionization mass spectrometry

A highly sensitive and specific assay was developed for the determination of clenbuterol in bovine plasma and tissues. Clenbuterol and the internal standard [2H9]clenbuterol were measured by gas chromatography-negative-ion chemical ionization mass spectrometry with methane as the reagent gas. Bovine tissues including muscle, liver, heart, kidney, lung, suet, brain, spinal cord and thymus were ground in a buffer of pH 7 and then extracted using ethyl acetate. After two subsequent purification steps, the cleaned-up organic extract was derivatized with pentafluoropropionic anhydride. The mass spectrometer was set to monitor the abundant ions m/z 368 and 377 of the perfluoroacyl derivatives. This assay was performed with 1 ml of plasma or 0.2 g of tissue. The feasibility of this method was demonstrated by the determination of clenbuterol residues as the femtomole level in a variety of tissues.

Quantitative measurement of clenbuterol at the femtomole level in plasma and urine by combined gas chromatography/negative ion chemical ionization mass spectrometry

A highly sensitive and specific assay was developed for the quantitative measurement of clenbuterol at the femtomole level in human plasma and urine. Clenbuterol and the internal standard (2H9)clenbuterol were measured by gas chromatography/negative ion chemical ionization mass spectrometry with methane as the reagent gas. The two compounds of interest were extracted from the biological samples at pH 13 using ethyl acetate. After two subsequent purification steps, the cleaned-up organic extract was derivatized with pentafluoropropionic anhydride. The mass spectrometer was set to monitor the abundant [M-HCl]- ions of the perfluoroacyl derivatives (m/z 368 and 377), which were generated in the ion source by an electron capture process. This assay required 1 ml of plasma or 0.5 ml of urine and the detection limit of the method was 5 pg ml-1 with a 12.8% relative standard deviation. The accuracy of the clenbuterol assay was also tested day to day with quality control specimens spiked blind to the analyst. The mean difference between the theoretical and actual values was lower than 4.1%.

Bitolterol. A preliminary review of its pharmacological properties and therapeutic efficacy in reversible obstructive airways disease

Bitolterol is a beta-adrenoceptor agonist which is hydrolysed to colterol by tissue esterases present at high concentrations in the lung. Animal studies indicate that bitolterol has significant beta 2-selectivity. In initial clinical trials transient cardiovascular effects have occurred in about 5% of patients. The spectrum of other adverse reactions with bitolterol is similar to that found with other beta-adrenoceptor agonists. Preliminary therapeutic trials of bitolterol administered by aerosol or nebuliser in adult patients with asthma have shown variable but significant improvements in forced expiratory volume in 1 second (FEV1) and a duration of action of up to 8 hours in some patients. Bitolterol has been shown to provide similar maximum increases in FEV1 to isoprenaline (isoproterenol) and to be significantly longer acting in long term comparative trials. Either alone or in combination with oral theophylline, bitolterol aerosol produces greater and more prolonged bronchodilation than oral theophylline alone but more consistently in non-steroid-dependent patients. Duration of bronchodilation with bitolterol in patients receiving steroids is less than in those who are not steroid dependent, perhaps due to more severe disease in the former group. More long term trials in larger groups of patients are clearly needed to assess the efficacy and safety of bitolterol in comparison with other long acting beta-adrenoceptor agents, and to define the role of bitolterol in the combination regimens of antiasthmatic agents which are becoming increasingly popular. Nevertheless, bitolterol appears to be a well tolerated and relatively long acting alternative to other beta-adrenoceptor agonists in the treatment of reversible obstructive airways disease.

Bitolterol mesylate: a beta-adrenergic agent. Chemistry, pharmacokinetics, pharmacodynamics, adverse effects and clinical efficacy in asthma

Bitolterol, (3-4 diester colterol) is a new beta 2-adrenergic agonist. Since it in itself is biologically inactive, bitolterol is considered a pro-drug. When administered it is activated within the lung by esterase hydrolysis to the active compound colterol catecholamine N-t-butyl-arterenol). In preclinical and clinical studies to date, bitolterol has proved to be an effective bronchodilator for adult and pediatric patients with chronic stable asthma and for some with chronic obstructive pulmonary disease. Bitolterol has been compared with other beta 2 agents, including isoproterenol, metaproterenol and albuterol. There is no evidence for cardiotoxicity when bitolterol is used in combination with theophylline in human studies. It is effective for control of exercise-induced asthma.