Adrenergic neurone blockers Sympathomimetics

ACE INHIBITORS, ADRENERGIC NEURONE BLOCKERS SYMPATHOMIMETICS i hypotensive effect. Note there is a risk of interactions even with topical sympathomimetics (eye and nose drops) Adrenergic neurone blockers act mainly by preventing the release of norepinephrine. Sympathomimetics stimulate adrenergic receptors, which causes a rise in BP Monitor BP at least weekly until stable... 

ADRENERGIC NEURONE BLOCKERS-GUANETHIDINE CENTRALLY ACTING ANTIHYPERTENSIVES-METHYLDOPA MAOIs Risk of adrenergic syndrome (see above). Reports of an enhanced hypotensive effect and hallucinations with methyldopa, which may cause depression Due to inhibition of MAOI, which breaks down sympathomimetics Avoid concurrent use. Onset may be 6-24 hours after ingestion... 

It is, however, interesting to observe that a good number of sympathomimetics in fact do not really mimic the actions of noradrenaline or adrenaline at the effector receptor. They merely induce the release of noradrenaline from the sympathetic postganglionic adrenergic nerves. Such sympathomimetics which exert their action indirectly are comparatively less effective in patients treated with noradrenaline depleting drugs, for instance, the rauwolfia alkaloids, or other adrenergic neuron blockers. 

By preventing the release of noradrenaline from adrenergic neurones, guanethidine and other adrenergic neurone blockers cause a temporary drug-induced sympathectomy , which is also accompanied by hypersensitivity of the receptors. This results in the increased response to the stimulation of the receptors by directly-acting sympathomimetics such as noradrenaline and phenylephrine. 

First, the extracts of the roots of Ruscus aculeatus at higher concentrations caused their contractions of canine cutaneous veins in part because the extracts could reveal an indirect sympathomimetic effect for the inhibition to the neuronal uptake such as cocaine (40) (Figure 11) of a serotonin-norepinephrine-dopamine reuptake inhibitor [31]. Here, a selective ai-adrenergic blocker prazosin (41) and a selective a2-adrenergic blocker rauwolscine (a-yohimbine. 42) (Figure 11) are present in the canine saphenous vein [32, 33] might greatly contribute to their contractile response to the extracts of the roots of Ruscus aculeatus. 

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