BiDil is a drug that has been around for a while, but has recently been marketed more agressively as a niche drug for treatment of congestive heart failure in self identified black patients. We have known for a long time that black patients respond differently to some drugs for the treatment of high blood pressure and congestive heart failure. The ACE (angiotensin converting enzyme inhibitor) and ARB (angiotensin receptor blocker) drugs that are highly effective antihypertensive agents in whites, are sometimes less effective in blacks. In addition congestive heart failure seems to be more prevalent in African Americans than in Euro Americans, and response to ACE and ARB in blacks with congestive heart failure is often less positive. The use of hydralazine is often found to be more effective in blacks, and isosorbide dinitrate used in combination with hydralazine gives better afterload reduction in blacks than ACE or ARB meds sometimes.
BiDil® is a combination of isosorbide dinitrate 25 mg with hydralazine 37.5 mg that is targeted at the niche of black patients with CHF. A study in 2005 in the NEJM showed the efficacy of this regimen with improved survival. This data was mined from a large study of CHF patients, and patients with CHF resulting from hypertension, especially black patients with CHF from hypertension, were found to benefit most from BiDil therapy.
I can remember when hydralazine was a mainstay of CHF therapy, prior to the approval of the ACE medications. The issue in those days was how to reduce afterload, a term that signifies the vascular resistance the heart pumps against, without causing bothersome hypotension. In caucasion patients now the ACE and ARB drugs are very effective at reducing afterload, but in at least some black patients, probably those who with hypertension caused heart failure, BiDil may be at least as effective. BiDil seems to be selectively effective in African Americans.
Hydralazine is one of the ingredients in BiDil. Hydralazine is a very old antihypertensive medication. Hydralazine is a direct vasodialator by functioning as a smooth muscle relaxant in the arterioles. Used alone hydralazine often loses efficacy after prolonged use, but in combination with a nitrate like isosorbide dinitrate it seems to maintain efficacy with longer term use.
Isosorbide dinitrate is a long-acting member of the nitrate family of medications. It leads to both veinous and arteriolar dilation, and is often used in patients with coronary artery disease. In conjunction with hydralazine it seems to be effective in black patients with congestive heart failure caused by longstanding hypertension.