Hydralazine
- Article last reviewed 25 February 2026
- 6 mins read
What is this medication for?
Hydralazine is used to treat high blood pressure. This medication works by relaxing blood vessels and helps to lower the blood pressure.
How should I take or use this medication?
- Do not stop taking your medication without checking with your healthcare professional.
- You may take this medication with or without food.
What should I do if I forget to take or use this medication?
If you forget to take a dose, just take the next dose at the usual time. Do not take two doses together to make up for the missed dose.
What precautions should I take when taking or using this medication?
Inform your healthcare professional if:
- You are allergic to this medication or any of the other ingredients of this medication.
- You are pregnant, planning to become pregnant, or breastfeeding.
- You are taking any other medications, including supplements, traditional medications and herbal remedies.
What are some common side effects of this medication?
Most of the side-effects listed here will improve with time. Speak with your healthcare professionals if any of them continues, worsens, or affects your daily life. Such side effects include:
- Dizziness and light-headedness
- This may occur especially when you change positions from a lying to sitting position or from a sitting to standing position. You can prevent this by getting up slowly or changing positions slowly. Take a rest by sitting or lying down if you feel dizzy.
- Headache
- Fast heartbeat and palpitations (feeling your heart beating)
- Flushing (reddening of the skin)
- Nausea
- Take the medication with or after food
- Take small but frequent meals and avoid fatty or spicy food
What are some rare but serious side-effects that I need to seek medical advice immediately?
The symptoms of a drug allergy include one or more of the following:
- Swollen face/eyes/lips/tongue
- Difficulty in breathing
- Itchy skin rashes over your whole body
You can also find out about drug allergies by watching these videos:
They are available in English, 中文, Melayu and தமிழ்: Drug Allergies
Rarely this medication may cause:
- Drug-induced lupus, where the patient develops symptoms similar to Systemic Lupus Erythematosus (SLE). The symptoms include a rash on the cheeks or other parts of the body, getting sunburnt easily, muscle or joint pain, chest pain or shortness of breath, or swelling in the arms or legs
- Liver problems. Symptoms include loss of appetite, severe nausea or vomiting, pain in the upper part of the stomach, yellowing of the skin or ‘whites’ of the eyes, dark-brown coloured urine and/or pale/clay-coloured stools
If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.
What food or medication should I avoid when I take or use this medication?
Avoid drinking alcohol as it may affect you more than usual and increase the side effects of the medication.
How should I store this medication?
Store in a cool and dry place below 30°C, away from direct sunlight and moisture. Keep this medication away from children.
How do I throw away this medication safely?
Pack this medication into a black trash bag and seal it tightly before throwing into the rubbish chute or bin.
Disclaimer
Please take note that the above is not a complete list of all possible side-effects. If you have any concerns about your medication or if you have other side-effects that you think are caused by this medication, please consult your doctor or pharmacist. If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.
This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (NHG Health, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.
Contributed By
- Pharmaceutical Society of Singapore