Methyldopa Sympathomimetics

Pseudoephedrine (Sudafed, Novafed, Afrinol, Others) [OTC] [Decongestant/Sympothomimetic] Uses Deconge tant Action Stimulates a-adren gic rec tors w/ vasoconstriction Dose Adults. 30-60 mg PO q6—8h Peds. 4 mg/kg/24 h PO qid -1- in renal insuff Caution [C, +] Contra Poorly controlled HTN or CAD, w/MAOIs Disp Tabs, caps, Liq SE HTN, insomnia, tach, arrhythmias, nervousness, tremor Interactions T Risk of HTN crisis W/ MAOIs T effects W/BBs, sympathomimetics X effects W/TCAs -1- effect OF methyldopa, reserpine EMS Found in many OTC cough/cold pr >arations use sympathomimetics w/ caution, may T adverse effects OD May cause N/V, HTN, arrhythmias, and Szs symptomatic and supportive... 

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... 

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... 

The most recent evidence suggests that the false transmitter hypothesis might, after all, furnish the better explanation of the mode of action of a-MMT. a-Methyl [p) tyrosine (a-MT) causes a loss of noradrenaline from the brain and, unlike a-MMT, it produces sedation in a number of animal species. a-MT also inhibits the conditioned avoidance response and this inhibition is correlated, to some extent at least, with a reduction in the noradrenaline content of the brain . It is also clear that the sympathomimetic activities of metaraminol and a-methylnoradrenaline are not so uniformly less than that of noradrenaline as was at first thought the relative potencies of these compounds depend very much on the species and preparation studied. There is also recent evidence that the replacement of noradrenaline by the false transmitters is accompanied by an increased sensitivity of the effector organs . It should, perhaps, be added that these facts, though welcome to the neuropharmacologist, make it even more difficult to explain the efficacy of a-methyldopa as a hypotensive agent. 

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