From the Guidelines
Hydralazine 50 mg twice daily is a suitable dose for managing hypertension, but it is essential to monitor blood pressure regularly and consider combination therapy with a diuretic and beta-blocker to optimize efficacy and minimize side effects. According to the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1, hydralazine is a direct vasodilator that can be used to treat hypertension, with a usual dose range of 100-200 mg/day, divided into 2 or 3 doses.
Key considerations when using hydralazine include:
- Monitoring for sodium and water retention, as well as reflex tachycardia, which can be mitigated by co-administering a diuretic and beta-blocker
- Risk of drug-induced lupus-like syndrome, particularly at higher doses
- Potential for orthostatic hypotension, especially in older adults
- Importance of regular blood pressure monitoring to ensure effectiveness and adjust the dose as needed
In clinical practice, hydralazine is often initiated at a lower dose and gradually increased to 50 mg twice daily as needed, with careful monitoring of blood pressure and potential side effects. The target blood pressure should generally be below 130/80 mmHg, but goals may vary based on comorbidities and age. If blood pressure remains uncontrolled on this dose, increasing to a maximum of 300 mg daily (divided doses) may be considered, or alternative medications might be added to the regimen, as recommended by the guideline 1.
From the FDA Drug Label
Although the precise mechanism of action of hydrALAZINE is not fully understood, the major effects are on the cardiovascular system. HydrALAZINE apparently lowers blood pressure by exerting a peripheral vasodilating effect through a direct relaxation of vascular smooth muscle The peripheral vasodilating effect of hydrALAZINE results in decreased arterial blood pressure (diastolic more than systolic);
- Hydralazine 50 mg bid is expected to lower blood pressure due to its peripheral vasodilating effect.
- The effect is more pronounced on diastolic blood pressure than on systolic blood pressure. 2
From the Research
Hydralazine and Blood Pressure
- Hydralazine is a medication used to treat high blood pressure, and its effectiveness can vary depending on the individual and the dosage used 3, 4, 5, 6, 7.
- A study published in 2011 found that intravenous hydralazine was commonly prescribed for non-urgent cases of hypertension in hospitalized patients, but its use was often unjustified due to the risk of hypotension and other adverse events 3.
- Another study published in 1984 compared the effectiveness of hydralazine with other antihypertensive agents and found that it was a suitable third-line treatment for patients with uncontrolled blood pressure 4.
- The dosage of hydralazine used in the studies varied, with one study using a dosage of 50 mg bid, but the effectiveness of this specific dosage is not well-established 5, 6, 7.
Effects of Hydralazine on Blood Pressure
- Hydralazine has been shown to lower blood pressure in patients with hypertension, but its effects can be variable and may depend on the baseline blood pressure 3, 4, 5, 6, 7.
- A study published in 1990 found that hydralazine increased sympathetic activity and had different effects on cardiac function compared to nifedipine, another antihypertensive medication 6.
- Another study published in 1986 compared the effectiveness of endralazine and hydralazine in patients with uncontrolled hypertension and found that endralazine was at least as effective as hydralazine in reducing blood pressure 7.
Safety and Tolerability of Hydralazine
- Hydralazine can cause adverse events, including hypotension, and its use should be carefully monitored in patients with hypertension 3, 4, 5, 6, 7.
- A study published in 1979 found that patients who were slow acetylators had significantly better blood pressure control and more side effects when taking hydralazine 5.
- Another study published in 1986 found that endralazine was better tolerated than hydralazine, with a lower drop-out rate and fewer cases of drug-induced lupus-like syndrome 7.