What is the maximum dose of hydralazine (Hydralazine) given in the Emergency Room (ER)?

From the Guidelines

The maximum dose of hydralazine in the emergency room setting is typically 20 mg per intravenous (IV) dose, which can be repeated every 4-6 hours as needed. For hypertensive emergencies, hydralazine is often administered as a 10-20 mg IV bolus, with careful blood pressure monitoring after administration 1. The onset of action is relatively quick, occurring within 10-30 minutes, and the fall lasts 2-4 hours. Hydralazine works as a direct arterial vasodilator, relaxing vascular smooth muscle and reducing peripheral resistance, which leads to decreased blood pressure. It's essential to monitor patients closely after administration as hydralazine can cause reflex tachycardia, headache, and precipitous drops in blood pressure. The medication should be used cautiously in patients with coronary artery disease, as the reflex tachycardia may increase myocardial oxygen demand. Some key points to consider when administering hydralazine include:

• Initial dose: 10 mg via slow IV infusion, with a maximum initial dose of 20 mg
• Repeat dose: every 4-6 hours as needed
• Monitoring: careful blood pressure monitoring after administration
• Side effects: reflex tachycardia, headache, and precipitous drops in blood pressure
• Contraindications: caution in patients with coronary artery disease, elderly patients, and those with renal impairment. Lower initial doses (5-10 mg) may be appropriate for these patients 1.

From the FDA Drug Label

When there is urgent need, therapy in the hospitalized patient may be initiated intramuscularly or as a rapid intravenous bolus injection directly into the vein. The usual dose is 20 to 40 mg, repeated as necessary The maximum dose of hydralazine given in the ER is not explicitly stated in the drug label.

• The label only mentions the usual dose of 20 to 40 mg, repeated as necessary.
• It does not provide a maximum dose limit. 2

From the Research

Maximum Dose of Hydralazine in the ER

• The maximum dose of hydralazine given in the Emergency Room (ER) is not explicitly stated in the provided studies 3, 4, 5, 6, 7.
• However, the studies discuss the use of hydralazine in the treatment of hypertensive emergencies and urgencies, and provide information on the dosing and administration of hydralazine in various clinical settings.
• According to the study by 4, the daily doses of hydralazine used in the study were 75,150, or 300 mg, and the maximum antihypertensive response (Emax) to hydralazine was 9.4 mm Hg.
• The study by 6 examined the effect of oral dose size on hydralazine kinetics and vasodepressor response, and found that the proportion of hydralazine that reaches systemic circulation increases with increasing dose size.
• The study by 5 provides information on the dosage, administration, and precautions for hydralazine, but does not specify a maximum dose for use in the ER.

Dosage and Administration

• The dosage and administration of hydralazine may vary depending on the clinical setting and the patient's condition 4, 5, 6.
• Hydralazine can be administered orally or intravenously, and the dose may be adjusted based on the patient's response to treatment 4, 5.
• The study by 4 found that the daily dose of hydralazine that elicited 50% of the maximum response (D50) was 0.87 mg/kg for slow acetylators and 1.68 mg/kg for fast acetylators.

Clinical Considerations

• The use of hydralazine in the ER should be guided by clinical judgment and careful monitoring of the patient's condition 3, 5.
• Hydralazine can cause adverse effects, such as hypotension, tachycardia, and headache, and should be used with caution in patients with certain medical conditions 5.
• The study by 7 discusses the antioxidant properties of hydralazine and its potential use in preventing nitrate tolerance, but does not provide information on the maximum dose of hydralazine for use in the ER.