hydralazine hydrochloride at a glance
Medicine class
Direct-acting arteriolar vasodilator
Main roles
Add-on treatment for hypertension or selected heart failure, and hospital treatment of hypertensive emergencies
Practical point
Tablets are swallowed with water; intravenous hydralazine is given by healthcare professionals in hospital
What is hydralazine hydrochloride used for?
The selected products are licensed in adults for:
Moderate to severe hypertension, with tablets used alongside other blood-pressure-lowering treatment
Chronic congestive heart failure when conventional treatment is insufficient, with tablets used alongside long-acting nitrates
Hypertensive emergencies, particularly those associated with pre-eclampsia or eclampsia, using intravenous treatment in hospital
Hypertension with renal complications, using intravenous treatment in hospital
How does hydralazine hydrochloride work?
Hydralazine mainly relaxes the muscle in small arteries, reducing resistance to blood flow and lowering arterial pressure. Its precise molecular mechanism is uncertain. This can trigger a faster heartbeat and fluid retention, helping explain why other cardiovascular treatments are often used alongside it.
hydralazine hydrochloride preparations and strengths
Tablet
Route: Oral
Strengths: 25 mg, 50 mg
Injection
Route: Parenteral
Strengths: 20 mg
How to take hydralazine hydrochloride
Follow the dispensing label and prescriber's instructions. Intravenous hydralazine is prepared and given by healthcare professionals with blood pressure and heart rate monitoring.
Swallow tablets with water.
Food can reduce absorption and effect, so follow the product-specific instructions and take tablets consistently in relation to meals.
Do not stop treatment without speaking to the prescriber; withdrawal may need to be gradual, particularly in heart failure.
hydralazine hydrochloride side effects
Common or expected effects
- Headache
- Fast heartbeat or palpitations
- Flushing or low blood pressure
- Nausea, vomiting, diarrhoea or other gastrointestinal disturbance
- Chest discomfort or angina
- Joint pain, joint swelling or muscle pain
- Lupus-like symptoms, particularly with prolonged exposure
Get urgent medical advice
- Severe allergic reaction, including breathing difficulty or facial or throat swelling
- New or worsening chest pain, severe palpitations or fainting
- Lupus-like reaction with fever, rash, joint pain, persistent malaise or chest pain
- Vasculitis or pulmonary–renal syndrome, which may cause breathlessness, coughing blood, swelling or blood in the urine
- Blood-cell disorders suggested by unusual infections, bruising, bleeding or marked tiredness
- Liver injury with yellow skin or eyes
- Kidney injury with reduced urine, swelling, nausea or breathlessness
hydralazine hydrochloride in pregnancy
Pregnancy requires specialist review. The tablet information advises avoiding hydralazine before the third trimester and using it later only when no safer alternative is suitable or the maternal condition presents serious risk. Intravenous hydralazine is licensed for hypertensive emergencies associated with pre-eclampsia or eclampsia, with close maternal and fetal consideration.
hydralazine hydrochloride while breastfeeding
Hydralazine passes into breast milk, but available reports have not identified adverse effects in breastfed infants. Breastfeeding may be possible when treatment is clinically necessary, following individual assessment and observation of the infant, especially if premature or unwell.
hydralazine hydrochloride interactions
Tell the prescriber or pharmacist about all medicines and alcohol use. Important examples include:
Other antihypertensives, nitrates, diuretics or vasodilators
Blood-pressure lowering may be increased, causing dizziness, faintness or hypotension.
Anaesthetics, tricyclic antidepressants, major tranquillisers and alcohol
These may enhance hypotension or central nervous system effects.
Common questions about hydralazine hydrochloride
Answers are fully visible for fast scanning and source review.
Why is hydralazine hydrochloride often prescribed with other heart or blood-pressure treatments?
It can trigger a faster heartbeat and fluid retention. A beta-blocker or another sympatholytic may limit the faster heartbeat, while a diuretic may reduce fluid retention. Nitrates are part of its licensed combination role in selected heart failure.
Can hydralazine hydrochloride cause lupus?
Prolonged exposure can cause a lupus-like syndrome, with possible joint pain, fever, rash, blood-count changes or chest symptoms. New suggestive symptoms require prompt clinical review.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.