Pharmacologic antagonism

Malick, J.B. Pharmacological antagonism of mouse-killing behavior in the olfactory bulb lesion-induced killer rat. Aggressive Behav 2 123-130,... 

Potassium-sparing diuretics prevent K+ secretion by antagonizing the effects of aldosterone at the late distal and cortical collecting tubules. Inhibition may occur by direct pharmacologic antagonism of mineralocorticoid receptors ( spironolactone, eplerenone ) or... 

Finally, application of the suspected substance should produce a response that mimics the action of the transmitter released by nerve stimulation. Furthermore, application of a selective antagonist should block the response. Microiontophoresis, which permits highly localized drug administration, has been a valuable technique in assessing the action of suspected transmitters. Because of the complexity of the CNS, specific pharmacologic antagonism of a synaptic response provides a particularly powerful technique for transmitter identification. 

Beta-1 Receptors. These receptors predominate in the heart and kidneys (see Table 18-2).9,24 The cardiac beta-1 receptors have received a tremendous amount of attention with regard to pharmacologic antagonism of their function through the use of the so-called beta blockers. 

In vitro studies have demonstrated that the exposure of cardiac myocytes to either ET-1 or All promoted hypertrophy, the reexpression of cardiac fetal genes, and the downregulation of SERCA2 mRNA (Shubeita et al. 1990 Sadoshima and Izumo 1993 Calderone et al. 2000 Strait et al. 2001). In the pressure-overloaded heart, myocardial ET-1 expression was increased and the pharmacological antagonism of... 

One of the adverse effects of reboxetine is difficulty in passing urine (SEDA-21,13). Eight patients taking reboxetine (4-8 mg/day) had troublesome urinary hesitancy (5). They were successfully treated with tamsulosin (0.4 mg/day), and in two patients tamsulosin was withdrawn after 2 weeks without recurrence of the urinary symptoms. Reboxetine is a selective noradrenaline reuptake inhibitor and may therefore produce urinary symptoms by activating i-adrenoceptors in the bladder, which tamsulosin would be expected to reverse. However, tamsulosin is also effective for urinary symptoms caused by other mechanisms, for example benign prostatic hyperplasia. Whether its apparent effectiveness in reboxetine -induced dysuria represents specific pharmacological antagonism is therefore uncertain. 

Chang, F.C.T., Hoffman, B.E., DeBus, S. (2002). Pharmacological antagonism of lethal effects induced by O-isobutyl S-2-(dieth-ylamino)ethyl]-methylphosphonothioate. Drug Chem. Toxicol. 25 321-37. 

Pharmacological antagonism. Sympathomimetics, e.g. amphetamine, phentolamine (present in anorectics and cold and cough remedies) may lead to loss of antihypertensive effect, and indeed to a hypertensive reaction when taken by a patient already on a P-adrenoceptor blocker, due to xmopposed a-adrenergic stimulation. 

This is most effectively achieved by physiological antagonism of bronchial muscle contraction, namely by stimulation of adrenergic bronchodilator mechanisms. Pharmacological antagonism of specific bronchoconstrictors is less effective either because individual mediators are not on their own responsible for a large part of the bronchoconstriction (acetylcholine, adenosine, leukotrienes) or because the mediator is not even secreted during asthma attacks (histamine). 

Pharmacologic antagonism between AZT and d4T High rate of early virological nonresponse seen in treatment-naive patients... 

Nondepolarizing blockade Neuromuscular paralysis that results from pharmacologic antagonism at the acetylcholine receptor of the end plate, eg, by tubocurarine... 

Other forms of antagonism In addition to pharmacologic antagonism, there are two other mechanisms by which a drug can inhibit or block the effects of an agonist ... 

Reid AA. Pharmacological antagonism between chlorpromazine and phenmetrazine in mental hospital patients. Med JAust (1964) 10,187-8. 

Bassett, M.L., Mullen, K.D., Skolnick, R, and Jones, E.A. 1987. Amelioration of hepatic encephalopathy by pharmacologic antagonism of the GABAA-benzodiazepine receptor complex in a rabbit model of fulminant hepatic failure. Gastroenterology 93 1069-1077. 

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