Tomaintain24-hour efficacyduring chronic therapy the drug must be administered every 6 to 8 hours. In
addition to the pharmacologic adverse effects often associated with vasodilators (flushing, headache, palpitations, arrhythmias, angina pectoris, myocardial infarction, and peripheral edema), the drug produces a lupus-like syndrome in
some patients usually after 6 to 24 months of therapy. The
interaction of the hydrazine moiety of hydralazine with DNA
to interfere with normal DNA methylation has been implicated in this condition,74
which almost always occursin slow
acetylators and is not predicted by a positive antinuclear
antibody (ANA)