Hold Parameters for Hydralazine 25mg PO
Hold hydralazine 25mg PO when systolic blood pressure is <100 mmHg or diastolic blood pressure is <60 mmHg, and always hold if the patient has symptomatic hypotension, heart rate >110 bpm (reflex tachycardia), or bradycardia <60 bpm. 1, 2
Blood Pressure Thresholds for Holding
Systolic BP <100 mmHg: Hydralazine causes direct vasodilation with unpredictable blood pressure responses lasting 2-4 hours, making administration at lower baseline pressures dangerous 3, 1, 2
Diastolic BP <60 mmHg: This is particularly critical because hydralazine preferentially lowers diastolic more than systolic pressure, and excessive diastolic lowering can compromise coronary perfusion, especially in patients with coronary artery disease 1, 2
Symptomatic hypotension at any BP: Hold regardless of numerical values if patient experiences dizziness, lightheadedness, or syncope 2, 4
Heart Rate Parameters for Holding
Heart rate >110 bpm: Hydralazine causes reflex tachycardia through baroreceptor-mediated sympathetic activation, which can precipitate anginal attacks and myocardial ischemia 2
Heart rate <60 bpm (bradycardia): The reflex tachycardia from hydralazine in a bradycardic patient creates unpredictable cardiovascular responses 3
New or worsening chest pain: Myocardial stimulation from hydralazine can cause anginal attacks and has been implicated in myocardial infarction 2
Clinical Context Considerations
When Hydralazine Should NOT Be Given
Acute hypertensive situations: Hydralazine is not a first-line agent for acute blood pressure management due to unpredictable response and prolonged duration of action 3, 5, 1
Without concurrent beta-blocker and diuretic: When used for chronic hypertension, hydralazine must be combined with these agents to counteract reflex tachycardia and sodium retention 5
Monotherapy for heart failure: Hydralazine without isosorbide dinitrate is contraindicated (Class III Harm) in heart failure with reduced ejection fraction 6, 5
Appropriate Use Context
Scheduled therapy with nitrate: The only evidence-based indication for oral hydralazine is as scheduled three-times-daily therapy combined with isosorbide dinitrate (37.5-75mg hydralazine with 20-40mg isosorbide dinitrate TID) for African American patients with NYHA class III-IV heart failure 6, 5
Resistant hypertension (fifth-line): Only as step 5 therapy at 25mg TID, titrated upward, with concurrent beta-blocker and diuretic 6, 5
Additional Hold Parameters
Signs of drug-induced lupus: Hold if patient develops arthralgia, fever, chest pain, or unexplained malaise, particularly with doses >150mg daily 2
Advanced aortic stenosis: Absolute contraindication due to unpredictable hemodynamic effects 5
Active coronary ischemia: The hyperdynamic circulation and myocardial stimulation can worsen ischemia 2
Severe renal impairment: Use with extreme caution; consider holding if creatinine significantly elevated 2
Common Pitfalls to Avoid
PRN dosing for asymptomatic hypertension: Studies show 36% of PRN hydralazine doses are given for BP <180/110 mmHg, which is inappropriate and associated with hypotension in 12% of cases 4, 7
Using instead of optimizing scheduled regimen: 62.4% of hospitalized patients receiving PRN hydralazine don't have their home antihypertensive regimens intensified, representing missed opportunities for appropriate management 7
Expecting predictable response: Blood pressure changes are highly variable (mean reduction 24/9 mmHg with standard deviation of 29/15 mmHg), making it unsuitable for precise BP control 4