Hydralazine is a medication primarily used to manage high blood pressure (hypertension) and treat heart failure. It is a direct-acting vasodilator that relaxes the smooth muscle in the walls of the arteries, causing blood vessels to widen. This action decreases resistance to blood flow and lowers systemic blood pressure. Because Hydralazine is a powerful agent capable of rapidly altering the body’s hemodynamics, knowing when to hold a dose is a fundamental safety measure.
Holding Hydralazine Due to Low Blood Pressure Readings
The most frequent reason to hold Hydralazine is hypotension, where the patient’s blood pressure falls below a safe limit. If the drug works too effectively, it can lead to inadequate blood flow to vital organs (hypoperfusion). For an average adult, a systolic reading below 90 to 100 mmHg, or a diastolic reading below 60 mmHg, is considered a threshold for holding the medication.
Patients should monitor their blood pressure, ideally before each scheduled dose. A reading significantly lower than the patient’s normal range may warrant a hold, even if slightly above the general threshold, especially if symptoms are present. Common signs of low blood pressure include feeling dizzy, lightheaded, or faint, particularly when moving to a standing position.
These symptoms occur because the sudden drop in pressure temporarily reduces the amount of blood reaching the brain. If a patient records a low reading or experiences signs of hypotension, they should hold the scheduled dose and immediately communicate the readings and symptoms to their healthcare provider. This action prevents the medication from compounding the low pressure.
Recognizing Severe Systemic Adverse Reactions
Hydralazine can cause rare but severe systemic adverse reactions that necessitate immediate cessation. The most notable is Hydralazine-induced lupus syndrome (HILS), an autoimmune reaction mimicking systemic lupus erythematosus (SLE). HILS typically takes months or years of continuous therapy to develop and is more common with higher daily doses.
Symptoms of HILS are often flu-like and can include joint pain, muscle aches, fever, and fatigue. While musculoskeletal symptoms are the most common, patients may also notice a rash, chest pain, or inflammation around the lungs or heart (serositis). If a patient develops these concerning symptoms, they should hold the medication and seek urgent medical evaluation.
Another severe reason for holding the drug is significant, persistent tachycardia (rapid heart rate), sometimes accompanied by chest pain (angina). Hydralazine can trigger a reflex response to lowered blood pressure, causing the heart to beat faster to compensate. While some reflex tachycardia is expected, a pronounced or painful increase in heart rate requires medical review, as it can be risky for individuals with underlying heart conditions.
Temporary Holds Based on Patient Condition or Procedure
Specific patient conditions and medical procedures may independently lower blood pressure or require tight control, necessitating a temporary hold of Hydralazine. Severe dehydration, often due to prolonged vomiting or diarrhea, can cause blood pressure to drop independently. Continuing Hydralazine in this volume-depleted state could lead to profound hypotension.
Elective surgical procedures frequently require temporarily holding certain blood pressure medications, and Hydralazine is often included in this group. Anesthesia and other surgical medications can cause blood pressure to drop, making continued use unnecessarily risky. The prescribing physician or surgical team provides specific pre-operative instructions detailing which medications to hold and for how long.
Consumption of alcohol can amplify the blood pressure-lowering effects of Hydralazine, increasing the risk of dizziness and fainting. Additionally, some medications, such as certain anti-nausea drugs, may increase the risk of hypotension when combined with Hydralazine. In these situations, the dose is held temporarily until the period of heightened risk has passed, always under the guidance of a healthcare professional.
What to Do After Holding a Dose
After holding a dose of Hydralazine due to low blood pressure, a systemic reaction, or situational risk, the immediate next step is contacting the prescribing physician. Patients should clearly communicate the reason for the hold, providing specific details like the blood pressure reading, symptoms, or upcoming medical procedure. This information allows the medical team to determine the cause and plan the next steps safely.
It is important not to resume the medication once symptoms subside without explicit medical advice. Resuming the drug may require a dosage modification or a complete change in medication, especially if a severe adverse reaction like HILS is suspected. If the hold was due to a low reading, the provider will likely instruct the patient to monitor their blood pressure closely and advise resuming only when readings stabilize into a safe range.
When stopping Hydralazine, avoid abruptly discontinuing the drug, as this can cause a rebound increase in blood pressure. If the medication needs to be stopped permanently, the physician will implement a gradual dose reduction schedule to ensure blood pressure remains controlled. Documenting the time the dose was held, recorded vital signs, and symptoms experienced provides valuable context for the medical professional during the follow-up consultation.