Hypotension sympatholytics

Welcome [67,68]. Bethanidine was initially patented as a hypotensive agent but was found to have antifibrillatory activity [69]. Attempts to limit the hypotensive effects of bethanidine led to meobentine. At a concentration of 44 fxM, bethanidine has minimal effects on APDioo in propranolol-treated and untreated canine Purkinje fibres (-1-2% and —5%, respectively) [70,71], At 350 //M in untreated fibres, bethanidine increased APDioo t>y about 6%. In contrast, meobentine, which has less sympatholytic activity, increased APDioo t>y 12% at 37 //M in untreated fibres during the same study. Both compounds showed modest decreases of V ax at the stated concentrations. The Class I activity and the sympatholytic activity (for bethanidine) may act to decrease the apparent Class III effects of the two compounds (see below). 

Antihypertensive drugs can be divided into eight classes based on the mechanism of action diuretics, )3-adrenoblockers, centrally acting sympatholytics, peripherally acting sympatholytics, calcium channel blockers, myotropic hypotensive drugs, angiotensin-con-verting enzyme inhibitors, and calcium channel activators. 

Sympathomimetic effects (from NA re-uptake inhibition) and antimuscarinic effects can cause a sinus tachycardia. Postural hypotension may occur as a result of sympatholytic al-adrenoceptor antagonism. With overdoses of these drugs, there is a reduced re-uptake of catecholamines, resulting in arrhythmias and hypertension. Tricyclic compounds have a high... 

These drugs are best avoided in patients with cerebrovascular, cardiovascular and hepatic disorders. Some sympathomimetic effects may occur, mainly mild tremor and occasionally cardiac arrhythmias. Apparent anticholinergic effects may also occur but these are the result of sympathetic potentiation in tissues with dual cholinergic/adrenergic innervation, e.g. pupil. Sympatholytic effects can also occur, principally postural hypotension, because of synthesis of relatively inactive false transmitters, e.g. octopamine, in nerve terminals following inhibition of MAO and activation of alternative metabolic pathways. 

A mixture of alkaloids from V. africana and V. obtuse have been shown to have cardiotonic, sympatholytic and hypotensive properties 9, 46, 47). 

Neuroleptic Interactions with the Noradrenergic q-Receptor - Autonomic sympatholytic effects such as orthostatic hypotension and sedation are among the most prominent untoward actions of neuroleptic drugs. These side effects have been attributed to blockade of central and peripheral adrenergic a-receptors39 0 1 but direct quantitative evaluation of a-receptor blockade in the CNS by these agents has not been heretofore feasible. In... 

TCAs may reverse the hypotensive effects of certain sympatholytic antihypertensives (e.g., guanethidine, methyldopa, and clonidine) because of inhibition of presynaptic uptake of the... 

Volume loss, venodilation, and arteriolar dilation are likely to result in hypotension with reflex tachycardia. In contrast, hypotension accompanied by bradycardia should suggest intoxication by sympatholytic agents, membrane-depressant drugs, calcium channel blockers, or cardiac glycosides or the presence of hypothermia. 

HYPOTENSION WITH RELATIVE BRADYCARDIA Sympatholytic agents... 

Sympatholytic syndrome. Blood pressure and pulse rate are both decreased (peripheral alpha blockers may cause hypotension with reflex tachycardia). The pupils are small, often of pinpoint size. Peristalsis is often decreased. (Examples centrally acting alpha-2 agonists [clonidine and methyidopa], opiates, and phenothiazines.)... 

IV. Diagnosis is based on the history of ingestion, accompanied by bradycardia and hypotension. Other drugs that may cause a similar presentation after overdose include sympatholytic and antihypertensive drugs, digitalis, and calcium channel blockers. 

IV. Diagnosis. The findings of hypotension and bradycardia, particularly with sinus arrest or AV block, in the absence of QRS interval prolongation should suggest calcium antagonist intoxication. The differential diagnosis should include beta blockers and other sympatholytic drugs. 

Urapidil is an alpha-blocker and has a central sympatholytic effect mediated by stimulation of central 5HTia receptors. The authors of a review have suggested that there is a lower incidence of tachycardia and orthostatic hypotension with urapidil than with other a-adrenoceptor antagonists and no apparent increased risk of heart failure [101 ]. 

Use in ambidatory patients patients with reduced circidating blood volume, impaired myocardial function or on sympatholytic drugs should be monitored for the possible occmrence of orthostatic hypotension, a frequent complication in single-dose neuraxial morphine analgesia Epidmal morphine should not be given to outpatient singical patients. 

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