Sympathomimetics, indirect

Sympathomimetics (indirect-acting) [HP] Hypertensive episode due to release of stored norepinephrine (amphetamines, ephedrine, isometheptene, phenylpropanolamine, pseudoephedrine). 

CENTRALLY ACTING ANTI HYPERTENSIVES SYMPATHOMIMETICS-INDIRECT 1. Indirect sympathomimetics may i the hypotensive effect of methyldopa 2. Methyldopa may 1 the mydriatic effect of ephedrine eye drops 1. Uncertain 2. Uncertain 1. Monitor BP at least weekly until stable 2. Watch for a poor response to ephedrine eye drops... 

BETA-BLOCKERS SYMPATHOMIMETICS -INDIRECT 1 hypotensive efficacy of beta-blockers The hypertensive effect of sympathomimetics opposes the hypotensive actions of beta-blockers Monitor BP at least weekly until stable watch for poor response to beta-blockers... 

VENLAFAXINE SYMPATHOMIMETICS -INDIRECT Case of serotonin syndrome when dexamfetamine is co administered with venlafaxine Uncertain postulated that there is an additive effect of inhibition of serotonin reuptake by venlafaxine, with a release of serotonin by venlafaxine Avoid co-administration... 

ANTICOAGULANTS-ORAL SYMPATHOMIMETICS -INDIRECT Methylphenidate may increase the efficacy of warfarin Uncertain at present Monitor INR at least weekly until stable... 

OPIOIDS SYMPATHOMIMETICS -INDIRECT Dexamfetamine and methyl-phenidate t analgesic effects and i sedation of opioids, when used for chronic pain Uncertain complex interaction between the sympathetic nervous system and opioid receptors Opioid requirements may be 1 when patients also take indirect sympathomimetics... 

Sympathomimetics (indirectly acting) Combining MAOis with agents such as amphetamines, cocaine, ephedrine, methylphenidate, pemoline, pseudoephedrine, phenylpropanolamine, and others (including many cold and allergy medications) can cause a potentially fatal hypertensive crisis. 

The manufaeturers eontraindieate the use of sympathomimetics (including adrenergic bronchodilators, pseudoephedrine, phenylpropanolamine, adrenaline (epinephrine), noradrenaline (norepinephrine), dopamine, dob-utamine) with linezolid unless there are faeilities available for close observation of the patient and monitoring of blood pressure. Some indirectly-aeting sympathomimetics occur in cough and cold remedies, whieh can be bought without prescription. To keep in line with the manufaeturers recommendations, patients should be told to avoid these preparations. However, it should be said that the evidenee available indicates that blood pressure rises are unlikely to be of the proportions seen with the antidepressant MAOIs, which result in hypertensive crises. Consider also MAOIs or RIMAs + Sympathomimetics Indirectly-acting , p.l 147. 

Switching from iproniazid to tranylcypromine/triftuoperazine may have been the cause of a fatal reaction (fever, shivering, sweating, cyanosis) in a patient also given ephedrine (see also MAOIs or RIMAs -i-Sympathomimetics Indirectly-acting , p. 1147). 

A single report describes a woman taking an MAOI who developed a severe occipital headache after taking 30 mL of a paediatric cough linctus. Initially this interaction was attributed to promethazine, but it is now known that the linctus in question contained phenylpropanolamine, which is much more likely to have been the cause. See N OIs or RIMAs + Sympathomimetics Indirectly-acting , p.ll47 for the interaction with phenylpropanolamine. 

For a brief mention of the treatment of hypertensive crisis, see Importance and Management under MAOIs or RIMAs + Sympathomimetics Indirectly-acting , p.ll47. For the management of fever and other symptoms of the serotonin syndrome, see Importance and management under MAOIs or RIMAs + Tricyclic and related antidepressants , p.ll49. 

These sympathomimetic amines act directly on the receptors at the nerve endings, which innervate arterial blood vessels, so that the presence of the MAOI-induced accumulation of noradrenaline within these nerve endings would not be expected to alter the extent of direct stimulation (contrast Sympathomimetics Indirectly-acting , (p.l 147)). The enhancement seen in those patients whose blood pressure was lowered by the MAOI might possibly be due to an increased sensitivity of the receptors, which is seen if the nerves are cut, and is also seen during temporary pharmacological severance . 

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