Indications
Hydralazine is used to treat high blood pressure, usually together with other blood pressure medicines when these alone are not enough. It is also used with Isosorbide dinitrate for some people with heart failure, and in hospital to lower dangerously high blood pressure, including severe high blood pressure in pregnancy (pre eclampsia).
How It Works
Hydralazine relaxes the muscle in the walls of the small arteries, so they widen. This lowers the resistance the heart pumps against and brings blood pressure down. Because the body may respond with a faster heartbeat and fluid retention, it is often given with a beta blocker and a diuretic (water tablet).
Dosage and Administration
Take it by mouth exactly as prescribed. For high blood pressure, adults are usually started on a low dose, such as 25 mg twice a day, and the doctor increases it gradually according to response; the maximum depends on the person and is set by the doctor. It can be taken with or without food, but take it the same way each day. Do not stop suddenly. Injections are given into a vein or muscle by a doctor or nurse in hospital.
Interactions
- Other blood pressure lowering medicines, nitrates, alcohol, some antidepressants and antipsychotics increase the fall in blood pressure.
- Diazoxide given with hydralazine can cause a severe drop in blood pressure.
- Non steroidal anti inflammatory drugs such as Ibuprofen and steroids may reduce its effect.
- Beta blockers such as Propranolol and Metoprolol may have higher blood levels, but are often used together on purpose.
Contraindications
- Allergy to hydralazine.
- Systemic lupus erythematosus (SLE) or related autoimmune conditions.
- Severe fast heart rate, high output heart failure, or heart failure caused by narrowing of a heart valve such as aortic or mitral stenosis.
- Heart failure caused by lung disease (cor pulmonale).
- Dissecting aortic aneurysm.
- Acute porphyria.
Side Effects
Common: headache, fast or pounding heartbeat, flushing, dizziness, nausea, vomiting, diarrhoea and ankle swelling, especially at the start. Less common: chest pain (angina), blocked nose, watery eyes, numbness or tingling in the hands and feet. With long term use or higher doses, a lupus like illness can occur, with joint pain, fever, rash and tiredness. Rare: blood count changes, liver problems.
Get urgent medical help for chest pain, fainting, a very fast or irregular heartbeat, severe joint pain with fever and rash, yellowing of the skin or eyes, unusual bleeding or bruising, or swelling of the face or throat.
Pregnancy and Lactation
Hydralazine has long been used to control high blood pressure in pregnancy, especially in later pregnancy, under a doctor’s care. Use in early pregnancy is avoided unless needed. Small amounts pass into breast milk and it is generally considered compatible with breastfeeding.
Precautions and Warnings
Use with care in people with coronary heart disease, recent stroke, kidney or liver disease. The doctor may check blood counts, kidney function and antinuclear antibodies during long term treatment. Dizziness can occur when standing up; rise slowly and take care when driving. Tell the doctor if you develop joint pains or unexplained fever.
Overdose
Overdose may cause a severe fall in blood pressure, a very fast heartbeat, chest pain, heart rhythm problems, flushing and fainting. Seek emergency medical care.
Therapeutic Class
Antihypertensive, direct acting vasodilator
Storage
Store below 30°C in a dry place, away from light and out of the reach of children. Injections: as directed on the pack.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.