A-adrenergic blocking agents

There is a decreased effectiveness of ritodrine when the drug is administered with a -adrenergic blocking agent such as propranolol and an increased risk of pulmonary edema when administered with the corticosteroids. Co-administration of ritodrine with the sym-pathomimetics potentiates the effect of ritodrine. Cardiovascular effects (eg, arrhythmias or hypotension) of ritodrine may increase when the drug is administered with diazoxide, general anesthetics, magnesium sulfate, or meperidine... 

In addition, other chemicals such as a-adrenergic blocking agents like chlorpromazine (O Flaherty and Thomas 1982 Way and Burrows 1976) or oxygen (Burrows et al. 1973 Sheehy and Way 1968) may be used to enhance the protective action of other antidotes. However, the mechanism of their action is not well understood. Further research for a potent and safe antidote, particularly among smoke inhalation victims who have carbon monoxide poisoning, to mitigate cyanide toxicity is desirable. 

Overdose may induce ventricular extrasystoles and short paroxysms of ventricular tachycardia, a sensation of fullness in the head, and tingling of the extremities. Should an excessive elevation of blood pressure occur, it may be immediately relieved by an a-adrenergic blocking agent, e.g., phentolamine. 

Dapiprazole HCl (Rev-Eyes) is an a-adrenergic blocking agent introduced for the treatment of iatrogenically induced mydriasis. One of the side effects of this topical agent is ptosis. In theory, this effect could potentially be useful for early eyelid retraction of Graves disease. Other side effects, however, include burning on instillation and moderate to severe conjimctival injection. There has been no published study about the efficacy of dapiprazole to relieve eyelid retraction in class 1 disease. 

Aloxidone and albutoine are anticonvulsivant V-allyl derivatives of hydantoin and thiohydantoin (Figure 20.21). The dibenzazepine azapetine is an a-adrenergic blocking agent used as peripheral vasodilator. 

Gillespie has employed fluorescence techniques to show that smooth muscle membrane can bind norepinephrine, and that this binding can be prevented by prior treatment with the a-adrenergic blocking agent, phenoxybenzamine. 

Phentolamine is a competitive nonselective a-adrenergic blocking agent. It reduces peripheral adrenergic tone and enhances cholinergic tone. As a result, it improves cavernosal filling and is proerectogenic. 

Certain vasogenic compounds, by themselves not antidotal, may have a potentiating effect on mechanistically antidotal materials. For example, chlorpromazine potentiates the antidotal effect of thiosulphate (Way and Burrows, 1976), and phenoxybenzamine, an a-adrenergic blocking agent, also potentiates thiosulphate. 

Among the more recent a-adrenergic blocking agents introduced for the treatment of high blood pressure was prazocin. 

Yohimbine is an a-adrenergic blocking agent and a serotonin antagonist. It depletes catecholamines from the mouse brain (Neuss, 1980). Yohimbine derivatives exhibit hypotensive and cardiostimulant activities (Cordell, 1981 Sz tay et al., 1986). 

Ekenvall L, Forsbeck M (1978) Contact eczema produced by a-adrenergic blocking agent (Alprenolol). Contact Dermatitis 4 190-194... 

Arcari, G., Bernardi, L., Bosisio, G., Coda, S., Fregnan, G.B. and Glaesser, A.H. (1972) 10-Methoxyergoline derivatives as a-adrenergic blocking agents. Experientia, 28, 819-820. 

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