Intravenous phentolamine test: diagnostic and prognostic use in reflex sympathetic dystrophy.

In some patients, ongoing and evoked neurogenic pain is relieved by pharmacological or destructive block of the sympathetic innervation of the affected part. In others, sympatholysis is ineffective. The present report shows that these two groups of patients can be distinguished by a safe and simple diagnostic test. Individuals in whom the pain was transiently relieved by intravenous phentolamine (Regitine) were very likely to respond favourably to subsequent sympatholytic treatment with i.v. regional guanethidine. Individuals in whom the phentolamine test was negative did not enjoy pain relief from this type of sympatholysis.