[Pharmacologic approach to autonomic failure].

Four different forms of primary autonomic failure (multiple system atrophy, pure autonomic failure, Parkinson's disease and dopamine beta-hydroxylase deficiency) have been described. The first part of the article will focus on the interest to pharmacology of elucidating pathophysiological mechanisms underlying autonomic involvement at the central level (growth hormone response to clonidine acute challenge), presynaptic level (plasma catecholamine levels after yohimbine administration) and on post-synaptic receptors (binding studies, pressor responses to noradrenaline). The second part will discuss efficacy and side-effects of some of the many drugs which are currently proposed for the treatment of one of the most disabling symptoms related to autonomic failure, orthostatic hypotension. Special attention will be paid to drugs acting on blood composition (fludrocortisone, erythropoietin), on post-synaptic alpha-adrenoceptors (midodrine and clonidine) and on noradrenaline spill-over (yohimbine and L-Threo-DOPS).