Agonists agents

Pharmacokinetics PO route onset rapid, peak 1-4 minutes, duration 15-75 minutes or 5 minutes if methacholine challenge is followed with a beta-agonist agent. Undergoes rapid hydrolysis in the plasma by acetylcholinesterase. 

Summary of adrenergic agonists. Agents marked with an asterisk ( ) are catecholamines. 

Table 3 Phosphatidylinositol assay from in vitro testing. Experimental agents causing an increase in intracellular free inositol phosphate accumulation are considered to be Group I agonists. Agents inhibiting inositol phosphate accumulation induced by ACPDa are considered to be Group I antagonists...

Dopamine agonists. Recent studies point to the possibility of neuroprotection from aging and parkinsonism by the administration of dopamine receptor agonists. Agents showing some promise include bromocriptine, a-dihydroergocryptine, lisuride and pergolide. 

Single doses of narcotic partial agonist agents, such as pentazocine, are reported to have no effect upon steady-state levels of both NA and DA, either in... 

Avermectins and Ivermectin. The avermectias are pentacycHc lactones isolated from fermentation products of Streptomjces avermitilis and ivermectin is a semisynthetic chemical, 22,23-dihydroavermectia (46). Ivermectin is effective in very low doses for the control of red spider mites on deciduous fmits, in baits for the control of imported fire ants, and as a parasiticide for Onchocerca volvulus in humans and for catde gmbs. These insecticides appear to function as agonists for the neuroinhibitory transmitter y-aminobutyric acid (GABA) (see Antiparasitic agents, avermectins). 

Nicotinic Receptor Agonists. There has been significant activity in the development of muscarinic cholinergic receptor agonists for dementia. In addition, agents that interact with nicotinic cholinergic receptors may also have therapeutic value. Nicotinic receptors have been reported to be... 

Phentolamine (87), WB 4101 (88), and the site directed alkylatiag agent, chloroethylclonidine (CEC) (89) have been traditionally used to define a -receptors. Table 6 Hsts the various catecholamines and adrenoreceptor agonists and antagonists. 

Aerosol adniinistration of isoproterenol produces a prompt (2—5 minutes) intense bronchodilatation of relatively short (1 h) duration. The lack of P2-selectivity leads, in many cases, to tachycardia and blood pressure elevation. Also, use of isoproterenol, like all other known P-agonists, results in a down-regulation, or desensitization, of P-adrenergic receptors. This desensitization is only partial, and after time (depending on dose, patient, and agent), a stable, less responsive state is achieved in which P-agonists remain effective. Isoproterenol has been widely used for many years. 

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