Hydralazine is a medication that causes vasodilation on the arterioles which ultimately leads to a reduction in blood pressure. It isn’t a medication that is used terribly often and I will discuss the reasons for this as well as other hydralazine clinical pearls you should be aware of.
Hydralazine Clinical Pearls – Why Isn’t It Used?
First, let’s talk about why the medication isn’t utilized very often. From an outpatient basis, this medication has to be dosed frequently due to a short half-life. Frequent dosing (3-4 times per day) for a chronic blood pressure reducing agent is not desirable at all. This is the primary reason why I see this medication avoided.
In addition to frequent dosing, hydralazine doesn’t have many compelling indications. ACE inhibitors, beta-blockers, and other blood pressure-lowering agents may have numerous compelling indications such as MI, diabetes, stroke, or other benefits in addition to the blood-pressure-lowering effects. In addition to not having many compelling indications, hydralazine is actually contraindicated in patients with coronary artery disease (CAD), and the more rare condition of mitral valve rheumatic disease.
When Might You See It?
In clinical practice, there are two primary situations that I have seen hydralazine used. The first situation is when we have exhausted all our other blood pressure-lowering medications. This may be due to intolerances or patients with very resistant hypertension. Always remember to look for medical or medication-induced hypertension causes in a patient with resistant hypertension.
The other situation that I have seen hydralazine used in clinical practice is in HFrEF. If you remember the ACC/AHA guidelines for heart failure, it is a potential option (in combination with a nitrate). The only time this option is used is typically when an ACE, ARB, or ARNI is not tolerable.
Adverse Effects
Hypotension is a potential consequence of any antihypertensive agents. Tachycardia in response to the vasodilation is a potential adverse effect with hydralazine. Although rare, hydralazine is also well known for its potential to cause a Lupus type reaction. Generally avoid this medication in patients with SLE. Also on the more unique side of things is the adverse effect of neuritis. Symptoms like numbness of the limbs can happen. Pyridoxine may be of help in patients who experience this adverse effect.
I discuss the pharmacology and more hydralazine clinical pearls on this podcast episode.
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It is very possible to use hydralazine twice daily, although it is ordered 3-4 times daily most often. I certainly try to get it ordered as BID as much as possible.
One other possible side effect is fluid retention as a result of vasodilation. it is possible that there is psuedohypertension as volume retention expands volume enough to overcome the effects of the vasodilation. For this reason, a diuretic is nearly always needed.
It is an uncommonly used drug, but very effective in the right setting (like every other drug to lower BP). It generally is a 3rd agent and most often used with a diuretic and something that slow ventricular response (BB, DHPCCB, and even clonidine work).
In many older patients, the reflex tachycardia does not occur.
There is no information about avoiding hydralazine in those with idiopathic lupus. What I would do is monitor for any arthritis, arthralgias. Drug-induced SLE can appear nearly identically to idiopathic SLE, but renal involvement is a reportable case.