A systematic review including 7 RCTs with a total of 101 subjects was abstracted in DARE. Two small studies (17 patients in total) showed some advantage of intravenous sympathetic regional blockade over control treatments. Neither of these studies involved guanethidine.
Comment: The quality of evidence is downgraded imprecise results (few patients and wide confidence intervals) and by study quality (poorly defined diagnostic criteria, inadequate wash-out periods, incomplete crossover, open administration of treatment, no description of technique and the high proportion of withdrawals with no intention to treat analysis).