Cadralazine challenge in patients with previous hydralazine-induced lupus: a 6-month study.

The objective of this study was to investigate the effect of cadralazine in patients who had previously had hydralazine-induced lupus. There were 11 patients included in the study, 10 of whom were treated for 6 months with 15 or 20 mg cadralazine given once daily in combination with beta-blockers and diuretics. All patients had a history of hydralazine-induced lupus and were slow acetylators. None of the patients included in this study showed any current signs or symptoms of drug-induced lupus. No evidence of lupus-like symptoms or of immunologic laboratory abnormalities were found during the study period. Side effects associated with vasodilator therapy were noted in some patients but were transient and mild. We concluded that a cross-reaction between cadralazine and hydralazine does not seem likely to occur and that cadralazine, because of its chemical properties, probably will not give rise to drug-induced lupus.