What is the role of intravenous (IV) hydralazine in treating severe hypertension?

From the Guidelines

Intravenous hydralazine is a viable option for treating severe hypertension, particularly in specific clinical scenarios, with an initial dose of 10 mg via slow IV infusion, which can be repeated every 4-6 hours as needed, as recommended by the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline 1. The use of IV hydralazine is supported by the guideline, which lists it as a vasodilator option for the treatment of hypertensive emergencies, with a usual dose range of 10 mg via slow IV infusion, repeat every 4-6 hours as needed. Some key points to consider when using IV hydralazine include:

• The onset of action is within 10-30 minutes, and the effect lasts 2-4 hours 1
• It is a direct vasodilator, which can cause a decrease in peripheral vascular resistance and a subsequent lowering of blood pressure
• IV hydralazine is particularly useful in pregnancy-related hypertensive emergencies, such as preeclampsia or eclampsia, and in acute heart failure with hypertension
• However, it should be used cautiously in patients with coronary artery disease, as it may cause reflex tachycardia
• Common side effects include headache, palpitations, flushing, and dizziness, and blood pressure should be monitored frequently during administration to prevent excessive drops in blood pressure. It's worth noting that while IV hydralazine is an effective option, it may not be the first-line therapy for all hypertensive emergencies, as more predictable agents like labetalol or nicardipine are often preferred, but it remains a valuable option in specific clinical scenarios, as outlined in the guideline 1.

From the FDA Drug Label

In hypertensive patients with normal kidneys who are treated with hydralazine, there is evidence of increased renal blood flow and a maintenance of glomerular filtration rate. The role of IV hydralazine in treating severe hypertension is to help lower blood pressure, but it must be used with caution in certain patients, such as those with:

• Suspected coronary artery disease
• Mitral valvular disease
• Advanced renal damage
• Cerebral vascular accidents It is essential to carefully weigh the benefits and risks of using hydralazine in these patients 2.

From the Research

Role of IV Hydralazine in Treating Severe Hypertension

• IV hydralazine is used to treat severe hypertension, particularly in pregnancy 3, 4, 5, 6
• It is one of the recommended first-line treatments for severe hypertension in pregnancy, along with labetalol and nifedipine 3
• However, studies have shown that nifedipine may be superior to hydralazine in terms of efficacy and safety 3, 4, 5
• IV hydralazine is often compared to other antihypertensive agents, such as labetalol and nifedipine, in terms of its effectiveness and safety profile 4, 5, 6

Comparison with Other Antihypertensive Agents

• Nifedipine has been shown to be superior to hydralazine in terms of successful treatment rate and time to achieve target blood pressure 5
• Labetalol and hydralazine have been shown to have similar efficacy, but nifedipine may have a better safety profile 3, 4, 6
• Other antihypertensive agents, such as diazoxide, nicardipine, and glyceryl trinitrate, have also been compared to hydralazine in terms of their efficacy and safety 6

Safety and Efficacy

• IV hydralazine has been associated with significant toxicities and adverse effects, such as maternal hypotension and fetal complications 7
• However, studies have also shown that hydralazine can be effective and safe when used in the treatment of severe hypertension in pregnancy 3, 4, 5, 6
• The choice of antihypertensive agent should be based on individual patient characteristics and clinical presentation 7