ABSTRACT
Symptomatic orthostatic hypotension is a fall in blood pressure on standing that leads to symptoms of cerebral hypoperfusion. Drug therapy of this entity is designed to alleviate symptoms with minimal side effects, and not just to treat the pressure falls. Correctable problems such as volume depletion or hypotensive medications must be dealt with initially. In autonomic failure, approaches (both drug and non-drug) are then tailored to reverse the operative pathophysiologic factors. Supine hypertension is often the major limiting factor to drug therapy. The assortment of drugs employed is testimony to the difficulty in finding effective agents in this disease.
Mineralocorticoids (9-alpha fludrocortisone) are the cornerstone of therapy. These drugs improve volume status and sensitize vessels to endogenous pressors. Other agents enhance sympathetic nervous system (SNS) activity. Yohimbine activates the SNS centrally, monoamine oxidase inhibitors prevent catecholamine breakdown, and dihydroxyphenylserine is a catecholamine precursor. Some drugs mimic sympathetic activity. Alpha agonists such as phenylpropanolamine, phenylephrine, ephedrine, midodrine, amphetamines and clonidine work as exogenous veno- and arteriolo-pressor agents. Other non-adrenergic vasopressors such as dihydroergotamine, caffeine, and cyclooxygenase inhibitors can also be tried. Miscellaneous agents also used include beta blockers, dopamine antagonists, and somatostatin and vasopressin analogues.
Drug usage is often additive and effectiveness is assessed empirically, using symptoms as the major monitored parameter. Pharmacologic therapy should go hand in hand with patient education and non-drug manoeuvres.
