Roy Massingham

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Competition experiments with [H]mepyramine showed that cetirizine and its enantiomers, levocetirizine and (S)-cetirizine, bound with high affinity and stereoselectivity to human H1 histamine receptors (Ki values of 6, 3, and 100 nM, respectively). Cetirizine and levocetirizine were 600-fold more selective for H1 receptors compared with a panel of receptors(More)
Competition experiments with [(3)H]mepyramine showed that cetirizine and its enantiomers, levocetirizine and (S)-cetirizine, bound with high affinity and stereoselectivity to human H(1) histamine receptors (K(i) values of 6, 3, and 100 nM, respectively). Cetirizine and levocetirizine were 600-fold more selective for H(1) receptors compared with a panel of(More)
PURPOSE To characterize the pharmacokinetics of cetirizine enantiomers in the guinea pig including protein binding in both the guinea pig and human plasma. METHODS Plasma concentrations of cetirizine enantiomers in the guinea pig were determined using a LC-MS/MS method after a short i.v. infusion (1, 2 and 4 mg/kg) of racemic cetirizine. Protein binding(More)
H1 receptors are involved in smooth muscle contraction and increasing vascular permeability observed in allergic diseases. Cetirizine (ZyrtecTM) and levocetirizine (XyzalTM) are second generation antihistamines. As opposed to first generation drugs exemplified by chlorpheniramine, second generation drugs are less sedative, due to an improved H1 binding(More)
Cetirizine (ZyrtecTM) and levocetirizine (XyzalTM) are second generation antihistamines prescribed for perennial rhinitis and urticaria. Both drugs display nanomolar affinity towards H1-histamine-receptors as determined in competition binding experiments performed against [3H]mepyramine [1]. Here we describe the binding properties of [3H]levocetirizine to(More)
Intravenous administration of N,N-di-n-propyldopamine (DPDA: 50 and 200 μg/kg/min, i. v.) produces hypotensive and bradycardic effects in anaesthetized cats and dogs. These effects were abolished by ganglionic blockade and antagonized by haloperidol or (SR)-sulpiride suggesting a neurogenic mechanism of action, mediated by specific dopamine receptors. The(More)
The selectivity of yohimbine and its two diastereoisomers rauwolscine and corynanthine for pre- and postsynaptic alpha adrenoceptors has been investigated in the anesthetized dog. Antagonism of the inhibitory effect of clonidine on the tachycardia produced by electrical stimulation of the ansa subclavia was used as a measure of presynaptic alpha-2(More)
1 LD 3098 (cirazoline) is an imidazoline derivative, possessing agonist properties at alpha-adrenoceptor sites.2 When transmitter release was measured directly as tritium overflow from perfused cat spleen preparations, prelabelled with [(3)H]-noradrenaline, LD 3098 was found to be 10 times more selective for presynaptic than for postsynaptic(More)
Bepridil, a calcium antagonist with anti-anginal, anti-ischemic, and anti-arrhythmic properties was assessed for its ability to scavenge free radicals. Bepridil reduced the stable free radical 1,1-diphenyl-2-picrylhydrazil (DPPH) in the molar ratio 2:1 and, in this respect, was as active as the reference anti-oxidants hydroquinone and alpha-tocopherol.(More)