From the FDA Drug Label
Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. The FDA drug label does not answer the question.
From the Research
The recommended oral dose of hydralazine for a single episode of hypertension is typically 10-25 mg, as stated in various clinical guidelines and studies, although the exact dose may vary depending on the specific clinical context and patient population. This initial dose can be repeated if necessary, but should be given at least 1-2 hours apart to assess response before administering additional medication. The maximum recommended single dose is 50 mg. Hydralazine works as a direct arterial vasodilator, relaxing vascular smooth muscle and reducing peripheral resistance, which leads to decreased blood pressure. The onset of action is relatively quick, occurring within 20-30 minutes after oral administration, with peak effects at 1-2 hours 1.
Some key points to consider when administering hydralazine for hypertension include:
- Monitoring blood pressure closely after administration to ensure appropriate response and to avoid excessive hypotension
- Being aware of potential side effects, such as reflex tachycardia, headache, flushing, and dizziness due to the vasodilation effect
- Considering dose reduction for patients with renal impairment
- Recognizing that hydralazine is not typically the first-line agent for hypertensive urgencies, with other medications like labetalol or clonidine often preferred due to more predictable responses 2, 3.
It's also important to note that the choice of antihypertensive medication and dosage may depend on various factors, including the severity of hypertension, presence of comorbidities, and individual patient characteristics. Therefore, it's essential to consult the latest clinical guidelines and evidence-based recommendations, such as those from the American Heart Association or the European Society of Cardiology, to ensure optimal management of hypertension 1.
In terms of specific studies, a 1982 study published in the British Medical Journal found that hydralazine was effective in reducing blood pressure, but its hypotensive effect waned at 24 hours, suggesting the need for repeated dosing or alternative treatment strategies 4. More recent studies, such as the 2018 review on pharmacologic management of hypertensive emergencies, highlight the importance of individualized treatment approaches and the need for ongoing monitoring and adjustment of antihypertensive therapy 1.