Hydralazine has a direct effect on the smooth muscle in the arterial wall. The molecular mechanism is unknown. The body reacts to the vasodilation by stimulating the sympathetic nervous system. This countereffect can be quite large, causing increased cardiac output and tachycardia. Hydralazine is used in combination with a β-blocker and/or diuretic. Hydralazine is important in hypertension and (pre-)eclampsia during pregnancy. Minoxidil
is a peripheral vasodilator. It opens ATP-driven potassium channels, which results in a direct hyperpolarization and relaxation of the arteriolar musculature. This drug is used to treat severe hypertension that does not respond to other drugs. Minoxidil retains salt and water, it activates the baroreceptor reflex and increases the heart frequency, myocardial contractility, cardiac output, and oxygen consumption of the heart. Like hydralazine, it is combined with a β-blocker and/or diuretic. Adverse effects of both drugs include tachycardia, palpitations, hypotension, and headache.
Hydralazine is known to cause systemic lupus erythrematosus (SLE). Your patient taking hydralazine comes to you with complaints of joint pain, weakness and fever. What objective data can confirm your suspicion of SLE?
Extra info: Anti-nuclear antibody test has a sensitivity = 99%; specificity = 49%. Leukopenia (white blood cell count<4000/ul): sensitivity = 59%; specificity = 89%. Antibodies to DNA are found to be the overall best discriminator.
Due to its effect on smooth muscle in the arterial wall, hydralazine will