What are the hold parameters for hydralazine (antihypertensive medication)?

Hold Parameters for Hydralazine

Hold hydralazine if systolic blood pressure is less than 100 mmHg or if the patient develops symptomatic hypotension, as the medication causes unpredictable and prolonged blood pressure reductions that can lead to adverse outcomes. 1, 2

Blood Pressure-Based Hold Parameters

Systolic Blood Pressure Thresholds

• Hold hydralazine when systolic BP falls below 100 mmHg, as the medication produces highly variable BP reductions (mean 24 mmHg systolic drop, but with standard deviation of ±29 mmHg) that are related to baseline BP values 2
• The unpredictability of BP response makes hydralazine particularly dangerous in patients with already-lowered BP, with hypotension being the most common adverse event (occurring in 11 of 94 patients in one study) 2

Symptomatic Hypotension

• Hold immediately if patient develops dizziness, lightheadedness, or other symptoms of hypotension, regardless of absolute BP number 1
• Effects last 2-4 hours after oral administration, meaning symptomatic hypotension can be prolonged 1

Heart Rate-Based Hold Parameters

Excessive Tachycardia

• Hold if heart rate exceeds 110-120 bpm or increases more than 20 bpm from baseline, as hydralazine causes reflex tachycardia that can be harmful, particularly in patients with coronary artery disease 1, 3
• This reflex tachycardia is why hydralazine must be combined with a beta-blocker in chronic use; if the patient is not on concurrent beta-blocker therapy, lower heart rate thresholds for holding should be considered 1, 3

Absolute Contraindications Requiring Permanent Hold

Cardiac Conditions

• Do not administer hydralazine in patients with advanced aortic stenosis due to unpredictable BP effects that can compromise coronary perfusion 1
• Hold in patients with acute coronary syndrome or unstable angina where reflex tachycardia could worsen myocardial ischemia 1

Drug-Induced Lupus

• Permanently discontinue if patient develops drug-induced lupus-like syndrome (arthralgia, fever, positive ANA), particularly at cumulative daily doses exceeding 200 mg 3
• Risk increases significantly with total daily doses above 150 mg 1

Clinical Context Considerations

Acute vs. Chronic Use

• For IV hydralazine in acute settings, hold if BP drops below 100/60 mmHg or more than 25% from baseline, as the ACC/AHA recommends against hydralazine as first-line for most acute hypertensive emergencies due to unpredictable responses 1
• For chronic oral therapy (particularly the hydralazine-isosorbide dinitrate combination in heart failure), hold if systolic BP consistently below 90-100 mmHg, as the mortality benefit demonstrated in trials required maintaining therapeutic dosing 1, 3

Monitoring Timing

• Check BP at 10-30 minutes, 1 hour, and 2-4 hours after each dose during initiation and titration, as peak effects occur within this window 3
• The short duration of action (2-4 hours) means BP can fluctuate significantly throughout the day with three-times-daily dosing 3

Common Pitfalls to Avoid

• Do not use hydralazine as monotherapy for hypertension without concurrent beta-blocker and diuretic, as reflex tachycardia and sodium retention will occur 1
• Do not use hydralazine without isosorbide dinitrate in heart failure, as this is associated with harm (Class III recommendation) 1
• Avoid administering the next dose if the previous dose caused symptomatic hypotension, even if current BP appears adequate 2