Reserpine Phenylephrine

Correct answer = D. Reserpine blocks the uptake of norepinephrine into intracellular storage vesicles, resulting in depletion of norepinephrine and gradual decline in blood pressure. Phenylephrine is a pure vasoconstrictor and raises systolic and diastolic blood pressures. Dopamine raises systolic and diastolic blood pressures by stimulating the heart and (at high doses) causing vasoconstriction. Ephedrine raises systolic and diastolic blood pressures by vasoconstriction and cardiac stimulation. Norepinephrine has a pressor effect. 

Patients taking certain systemic medications are also more sensitive to the pressor effects of phenylephrine. In individuals taking atropine, the pressor effect of phenylephrine is augmented, and tachycardia can occur. Tricyclic antidepressants and monoamine oxidase (MAO) inhibitors also potentiate the cardiovascular effects of topical phenylephrine. The concomitant use of phenylephrine is contraindicated with these agents, even up to 21 days after cessation of MAO inhibitor therapy. Similarly, patients taking reserpine, guanethidine, or methyldopa are at increased risk for adverse pressor effects from topical phenylephrine because of denervation hypersensitivity accompanying the chemical sympathectomy. 

Contraindications to the topical use of hydroxyamphetamine for routine mydriasis are similar to those to phenylephrine. Because of its tachyphylaxis and ineffectiveness in postganglionic denervation, however, hydroxyamphetamine may be a safer mydriatic for use in patients with insulin-dependent diabetes, idiopathic orthostatic hypotension, or chemical sympathectomy produced by therapy with systemic guanethidine, reserpine, or methyl-dopa. Thus hydroxyamphetamine seems to be less strongly contraindicated than phenylephrine for certain high-risk patients. 

Patients taking monoamine oxidase inhibitors, anticholinergic drugs (such as tricyclic antidepressants), propranolol, reserpine, guanethidine, and methyldopa should be monitored closely if phenylephrine is used (SEDA-16, 542) (16). 

Clinically important, potentially hazardous interactions with alcohol, amiodarone, beta-blockers, cimetidine, donidine, digoxin, diltiazem, disopyramide, ephedrine, epinephrine, ergot alkaloids, guanethidine, halothane, isoprenaline, lidocaine, noradrenaline, NSAIDs, phenylephrine, quinidine, reserpine, verapamil... 

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