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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The effects of fetal intravenous treatment with phentolamine or a vasopressinergic V1-receptor antagonist on the fetal cardiovascular responses to acute hypoxaemia in the llama were investigated. 2. Six llama fetuses were surgically prepared between 60 and 70 % of gestation under general halothane anaesthesia with vascular catheters and transit-time ultrasonic flow probes around a carotid artery and a femoral artery. At least 4 days after surgery all fetuses were subjected to a 3 h experiment: 1 h of normoxia, 1 h of hypoxaemia and 1 h of recovery while on slow i.v. infusion with saline. On separate days this experiment was repeated with fetal i.v. treatment with either phentolamine or a V1-receptor antagonist dissolved in saline. 3. During saline infusion all llama fetuses responded to acute hypoxaemia with intense femoral vasoconstriction. Phentolamine during normoxia produced hypotension, tachycardia and vasodilatation in both the carotid and the femoral circulations. During hypoxaemia, fetuses treated with phentolamine did not elicit the pronounced femoral vasoconstriction and all died within 20 min of the onset of hypoxaemia. A V1-receptor antagonist produced a femoral vasodilatation during normoxia but did not affect the fetal cardiovascular responses to acute hypoxaemia. 4. In conclusion, alpha-adrenergic and V1-vasopressinergic mechanisms contribute to a basal vasoconstrictor tone in the femoral circulation in the llama fetus. The enhanced femoral vasoconstriction during acute hypoxaemia in the llama fetus is not mediated by stimulation of V1-vasopressin receptors, but is dependent on alpha-adrenergic receptor stimulation. Such alpha-adrenergic efferent mechanisms are indispensable to fetal survival during hypoxaemia in the llama since their abolition leads to cardiovascular collapse and death.
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PMID:Adrenergic and vasopressinergic contributions to the cardiovascular response to acute hypoxaemia in the llama fetus. 992 92

Vasomax is an oral preparation of phentolamine mesilate (Zonagen Pharmaceuticals) currently undergoing worldwide regulatory approval for distribution. Phentolamine is primarily an alpha-adrenergic antagonist with mild sympatholytic action and a beta-adrenergic stimulating action. Over 30 years of clinical experience has shown it to be a strong direct vasodilator on muscular walled vessels, likely based on its inhibitory action on adenosine 5-triphosphate-sensitive potassium channels. This medication is not new, having been marketed in the United States in an oral formulation between 1952 and 1984. Phentolamine initially achieved FDA approval for preoperative use in patients with pheochromocytoma for control of blood pressure and paroxysmal hypertensive episodes. In the past it had been evaluated for hypertension, pulmonary disease, cardiac arrhythmias, angina pectoris and peripheral vascular disease. Unfortunately for most of these indications the clinical responses to oral phentolamine have been variable. The most clinically significant adverse events associated with oral phentolamine in the past were systemic hypotension and vasomotor collapse, severe gastrointestinal side effects especially diarrhea and some complaints of nasal congestion. In this review we will concentrate on phentolamine in a new preparation for on demand treatment of erectile dysfunction of mild to moderate degrees.
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PMID:Oral phentolamine (Vasomax). 1287 9