From the FDA Drug Label
HydrALAZINE is rapidly absorbed after oral administration, and peak plasma levels are reached at 1 to 2 hours. The oral dose of 25 mg Hydralazine is absorbed quickly, with peak plasma levels reached within 1 to 2 hours 1.
- The half-life of Hydralazine is 3 to 7 hours.
- Plasma levels of Hydralazine vary widely among individuals.
- Dosing may need to be adjusted based on individual response, particularly in slow acetylators who may require lower doses.
From the Research
Hydralazine 25 mg is an appropriate oral dose for initiating treatment of hypertension in adults, as it works as a direct vasodilator, relaxing vascular smooth muscle to reduce blood pressure. The typical starting dose is 10-25 mg taken orally 2-4 times daily, with gradual increases as needed to achieve blood pressure control 2. When taking hydralazine, patients should be aware that it may cause headache, dizziness, reflex tachycardia, and fluid retention, especially when treatment begins. Taking the medication with food can help minimize gastrointestinal side effects. Blood pressure should be monitored regularly while using this medication. Long-term use requires monitoring for potential development of drug-induced lupus-like syndrome, which is more common at higher doses.
Some key points to consider when prescribing hydralazine include:
- The maximum recommended daily dose is 300 mg divided throughout the day
- Hydralazine is often prescribed alongside a beta-blocker to counteract reflex tachycardia and a diuretic to prevent fluid retention, particularly when used for moderate to severe hypertension
- Acetylator status may not be a significant predictor of response to hydralazine, but age may play a role in the magnitude of response, with older patients experiencing greater falls in peripheral resistance per milligram hydralazine administered 2
- Side effects are related to the magnitude of fall in peripheral resistance, and patients should be monitored closely for these effects
It's also important to note that hydralazine may be used in combination with other medications, such as nitrates, for the treatment of heart failure, as part of the BANDAID(2) mnemonic, which represents best practice for the treatment of systolic heart failure 3. However, the primary focus of hydralazine 25 mg is on the treatment of hypertension, and its use should be guided by the most recent and highest quality evidence available, which may not always be conclusive due to the lack of randomized controlled trials comparing hydralazine to placebo 4.