Apresolin (Hydralazine)
Direct-acting vasodilator for high blood pressure and heart failure
Quick Facts About Apresolin
Key Takeaways About Apresolin
- Used for resistant hypertension and heart failure: Apresolin is prescribed when standard blood pressure medications have not provided adequate results, often in combination with beta-blockers or diuretics
- Watch for lupus-like symptoms: Long-term use can cause a drug-induced lupus-like syndrome — contact your doctor immediately if you develop joint pain, fever, or skin rash
- Dosage is individualized: Your doctor will start with a low dose and gradually increase it based on your blood pressure response
- Do not stop abruptly: Never stop taking Apresolin without consulting your doctor, as sudden discontinuation may cause a rebound increase in blood pressure
- Acetylator status matters: Whether you are a slow or fast acetylator affects how your body processes hydralazine and may influence dosing and side effect risk
What Is Apresolin and What Is It Used For?
Apresolin (hydralazine hydrochloride) is a prescription vasodilator medication used to treat high blood pressure (hypertension) and heart failure when standard treatments have not provided satisfactory results. It works by directly relaxing the smooth muscle in arteriole walls, reducing peripheral vascular resistance and lowering blood pressure.
Hydralazine, the active ingredient in Apresolin, belongs to a class of medications known as direct-acting vasodilators. Unlike many other antihypertensive drugs that work through the nervous system or hormonal pathways, hydralazine acts directly on the smooth muscle cells lining the walls of small arteries (arterioles). By causing these blood vessels to relax and widen, it reduces the resistance that blood encounters as it flows through the arterial system, thereby lowering blood pressure.
In the context of heart failure, the vasodilatory effect of Apresolin serves a particularly important role. By reducing peripheral vascular resistance (afterload), the medication decreases the amount of work the heart must perform to pump blood throughout the body. This reduction in cardiac workload allows the heart to pump more efficiently, improving cardiac output and helping to alleviate symptoms of heart failure such as shortness of breath, fatigue, and fluid retention.
Apresolin has been used in clinical practice since the 1950s and remains an important medication in cardiovascular medicine. It is included on the World Health Organization (WHO) Model List of Essential Medicines, reflecting its importance in global healthcare. The drug is particularly valued in certain clinical scenarios, including the management of hypertensive emergencies in pregnancy and as part of combination therapy for heart failure in specific patient populations.
Hydralazine is also available in combination with isosorbide dinitrate (marketed as BiDil in some countries), which has demonstrated particular benefit in the treatment of heart failure in certain patient groups. The combination provides both arterial vasodilation (hydralazine) and venodilation (isosorbide dinitrate), offering complementary hemodynamic effects.
Apresolin is typically not used as a first-line treatment for hypertension. It is most commonly prescribed in combination with other antihypertensive medications, particularly beta-blockers (to counteract reflex tachycardia) and diuretics. Your doctor will determine the most appropriate treatment plan for your specific situation.
What Should You Know Before Taking Apresolin?
Before starting Apresolin, inform your doctor about all medical conditions, particularly kidney disease, heart conditions, or autoimmune disorders. Apresolin is contraindicated in patients with systemic lupus erythematosus (SLE) and should not be used in certain heart conditions. Several medications can interact with hydralazine.
Contraindications
You should not take Apresolin if any of the following apply to you:
- Allergy to hydralazine, dihydralazine, or any excipient — If you have a known hypersensitivity to the active substance or any of the inactive ingredients in Apresolin tablets
- Systemic lupus erythematosus (SLE) — Or similar autoimmune connective tissue disorders where the body's immune system attacks healthy tissues, affecting skin, joints, kidneys, brain, and other organs
- Tachycardia-related conditions — If you have symptoms or complications caused by a rapid heart rate
- Dissecting aortic aneurysm — A tear in the wall of the aorta (the body's largest artery), as vasodilation could worsen this life-threatening condition
Warnings and Precautions
Talk to your doctor, pharmacist, or nurse before taking Apresolin if you have any of the following conditions, as your treatment may need to be carefully monitored or your dose adjusted:
- Severely impaired kidney function — The kidneys play a role in eliminating hydralazine from the body, so reduced kidney function may require dose adjustment
- Heart failure with low blood pressure — While Apresolin can help in heart failure, it must be used cautiously when blood pressure is already low
- Any heart disease — Including coronary artery disease, as the reflex tachycardia caused by hydralazine can increase myocardial oxygen demand
- Angina pectoris — Chest pain caused by reduced blood flow to the heart may be worsened by reflex tachycardia
- Cerebrovascular disease — Conditions affecting the blood vessels that supply the brain, as sudden blood pressure changes may be harmful
- Acetylator status — If you know whether you are a slow or fast acetylator, inform your doctor. Slow acetylators metabolize hydralazine more slowly, which may increase the risk of side effects, particularly drug-induced lupus. Your doctor may need to adjust your dose accordingly.
Treatment with Apresolin can cause a lupus-like syndrome (SLE-like syndrome). Contact your doctor immediately if you develop symptoms such as joint pain, fever, skin rash, pale skin, weakness, shortness of breath, or easy bruising and bleeding. This risk is higher with higher doses (typically above 200 mg daily), prolonged treatment, and in slow acetylators. The condition is usually reversible upon discontinuation of the drug.
Apresolin can cause inflammation of blood vessel walls (vasculitis), which may lead to pulmonary-renal syndrome — a serious and potentially life-threatening condition. Contact your doctor immediately if you experience fever, loss of appetite, weight loss, fatigue, generalized body pain, coughing up blood, swollen feet and ankles, or blood in your urine during treatment.
Pregnancy and Breastfeeding
If you are pregnant, breastfeeding, think you may be pregnant, or are planning to have a baby, consult your doctor or pharmacist before using this medicine.
Pregnancy: No adverse effects on the fetus have been demonstrated with hydralazine. However, always consult your doctor if you are pregnant or may become pregnant during treatment. Hydralazine is actually one of the few antihypertensive medications that has a relatively established safety profile in pregnancy and is sometimes used under careful medical supervision to manage severe hypertension in pregnancy, including pre-eclampsia.
Breastfeeding: Hydralazine passes into breast milk but is unlikely to affect the nursing infant at therapeutic doses. Mothers taking Apresolin may breastfeed their infant, provided the baby is monitored for any unexpected effects. Discuss this with your healthcare provider to make an informed decision.
Driving and Using Machinery
Some patients may experience dizziness or low blood pressure during treatment with Apresolin. These effects can impair your ability to drive or operate machinery safely. Be aware of how you personally react to this medication before engaging in activities that require alertness. If you experience dizziness, lightheadedness, or fainting, avoid driving and operating heavy machinery until these symptoms resolve.
Apresolin tablets contain sucrose (a type of sugar). If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicine.
How Does Apresolin Interact with Other Drugs?
Apresolin can interact with several other medications, potentially enhancing or diminishing their effects. Always tell your doctor about all medications you are taking, including prescription drugs, over-the-counter medicines, and herbal supplements. Key interactions include other blood pressure medications, NSAIDs, and certain antidepressants.
Drug interactions with hydralazine can be clinically significant and may require dose adjustments or additional monitoring. The most important interactions involve medications that also affect blood pressure or cardiovascular function, as the combined effects can lead to excessive blood pressure lowering (hypotension) or other adverse effects.
| Interacting Drug | Effect | Severity | Recommendation |
|---|---|---|---|
| Indomethacin (NSAIDs) | May reduce the blood pressure-lowering effect of Apresolin | Moderate | Monitor blood pressure closely; dose adjustment may be needed |
| Beta-blockers (e.g., propranolol) | Enhanced blood pressure-lowering effect; beta-blockers also help counteract reflex tachycardia | Moderate | Often used intentionally in combination; monitor closely |
| Calcium channel blockers | Enhanced blood pressure-lowering effect | Moderate | Monitor for excessive hypotension |
| ACE inhibitors | Enhanced blood pressure-lowering effect | Moderate | Monitor blood pressure; dose adjustment may be needed |
| Diuretics | Enhanced blood pressure-lowering effect | Moderate | Often used in combination; start with low doses |
| Tricyclic antidepressants | Enhanced blood pressure-lowering effect | Moderate | Monitor for orthostatic hypotension |
| MAO inhibitors | Enhanced blood pressure-lowering effect | Major | Use with caution; close medical supervision required |
| Sympathomimetics (e.g., epinephrine) | Should not be used to treat hypotension caused by Apresolin | Major | Avoid in Apresolin-induced hypotension; use alternative vasopressors |
Alcohol Interaction
Alcohol can enhance the blood pressure-lowering effect of Apresolin, potentially causing excessive hypotension (dangerously low blood pressure). This may lead to dizziness, lightheadedness, fainting, and falls. It is advisable to limit or avoid alcohol consumption while taking Apresolin. If you do drink alcohol, do so in moderation and be aware of how it affects you in combination with your medication.
Food Interactions
Apresolin can be taken with or without food. However, food may affect the absorption rate of hydralazine. Taking the medication consistently with regard to meals (always with food or always on an empty stomach) can help maintain more stable blood levels. Discuss with your pharmacist or doctor whether there are specific dietary considerations for your individual treatment plan.
What Is the Correct Dosage of Apresolin?
The dose of Apresolin is individualized by your doctor based on your condition and response to treatment. For hypertension, the usual starting dose is 25 mg once or twice daily, gradually increased. For heart failure, the usual starting dose is 25 mg three times daily. Never change your dose without consulting your doctor.
Apresolin should always be taken exactly as prescribed by your doctor. The dose is carefully titrated (gradually adjusted) based on your blood pressure response and tolerance to the medication. Your doctor will typically start with a low dose and increase it slowly over several weeks to minimize side effects, particularly reflex tachycardia and hypotension.
Adults — High Blood Pressure (Hypertension)
Hypertension Dosing Schedule
- Week 1: 25 mg (1 tablet) once or twice daily
- Week 2: 25 mg three times daily or 50 mg (2 tablets) twice daily
- Subsequent weeks: Dose may be gradually increased as needed, up to 50–200 mg daily in divided doses
- Maintenance: Once satisfactory blood pressure control is achieved, the dose should be reduced to the lowest effective maintenance dose
Note: For hypertension, Apresolin should be combined with other antihypertensive agents, particularly beta-blockers or diuretics, to counteract reflex tachycardia and fluid retention.
Adults — Heart Failure
Heart Failure Dosing Schedule
- Starting dose: 25 mg (1 tablet) three times daily
- Titration: If needed, the dose may be gradually increased at one-week intervals
- Maximum dose: Up to 75 mg (3 tablets) three times daily
Note: In heart failure, Apresolin should be used as an add-on to treatment with cardiac glycosides (digitalis) and diuretics.
Children
Apresolin is not recommended for use in children. There is insufficient evidence regarding the safety and efficacy of hydralazine in pediatric patients. If a child requires antihypertensive treatment, your doctor will prescribe an appropriate medication with an established pediatric safety profile.
Missed Dose
If you forget to take a dose of Apresolin, take it as soon as you remember unless it is almost time for your next scheduled dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a forgotten tablet, as this could cause your blood pressure to drop too low.
Overdose
If you have taken too much Apresolin, or if a child has accidentally swallowed the medication, contact emergency medical services or a poison control center immediately. Symptoms of overdose may include:
- Severe low blood pressure (hypotension) and rapid heart rate (tachycardia)
- Nausea, dizziness, and excessive sweating
- Severe chest pain and irregular heart rhythm (cardiac arrhythmia)
- Headache, vomiting, tremors, and seizures
- Decreased urine output or low body temperature (hypothermia)
Stopping Treatment
Do not stop taking Apresolin without first consulting your doctor. Abrupt discontinuation of antihypertensive therapy can lead to a rebound increase in blood pressure, which may be dangerous. If it is necessary to stop the medication, your doctor will typically reduce the dose gradually over a period of time.
What Are the Side Effects of Apresolin?
Like all medicines, Apresolin can cause side effects, although not everybody gets them. The most common side effects are headache and palpitations (rapid or irregular heartbeat). More serious but less common effects include drug-induced lupus-like syndrome, vasculitis, and kidney problems. Contact your doctor immediately if you experience severe symptoms.
Side effects of hydralazine vary in frequency and severity. Many of the common side effects, particularly headache and palpitations, tend to occur at the start of treatment or when the dose is increased rapidly, and often improve with continued use as the body adjusts to the medication. However, some side effects can be serious and require immediate medical attention.
- Signs of infection with severe deterioration — fever with sore throat or difficulty urinating (may indicate agranulocytosis, a very rare reduction in white blood cells)
- Cloudy or foamy urine (proteinuria) — with ankle swelling and high blood pressure (may indicate acute kidney inflammation)
- Joint pain, fever, skin rash, pale skin, weakness — shortness of breath and easy bruising (may indicate drug-induced lupus-like syndrome)
- Chest pain radiating to arm or neck, shortness of breath — may indicate angina pectoris
- Fever, appetite loss, weight loss, coughing up blood — swollen feet and blood in urine (may indicate vasculitis/pulmonary-renal syndrome)
- Yellowing of skin/eyes, pale stool, dark urine — may indicate hepatitis and jaundice
Very Common
- Headache
- Palpitations (rapid or irregular heartbeat) — especially at treatment start or rapid dose increases; usually transient
Common
- Positive ANF (Anti-Nuclear Factor) blood test — may indicate autoimmune activity
- Drug-induced lupus-like syndrome (SLE-like syndrome) — joint pain, fever, skin rash
- Low blood pressure (hypotension)
- Flushing
- Nausea and vomiting
- Diarrhea and gastrointestinal disturbances
- Joint pain, joint swelling, and muscle pain
- Angina pectoris (chest pain)
Uncommon
- Hypersensitivity reactions (hives, itching)
- Dizziness
- Fluid retention (edema)
- Loss of appetite
- Anxiety and restlessness
- Nasal congestion
- Shortness of breath and pleuritic pain
- Fever and general malaise
- Increased tearing and conjunctivitis
- Anemia and low platelet count (increased bleeding risk)
- Proteinuria (excess protein in urine)
- Vasculitis leading to pulmonary-renal syndrome
- Hepatitis and jaundice
- Heart failure
Rare
- Depression
- Hallucinations
- Exophthalmos (protruding eyes)
Very Rare
- Numbness and tingling in arms and legs (paresthesia)
- Tremors
- Paradoxical blood pressure increase
- Peripheral neuropathy (nerve damage causing numbness, tingling, or weakness)
- Urinary retention (inability to empty the bladder)
- Lymph node disease (lymphadenopathy)
- Enlarged spleen (splenomegaly)
- Agranulocytosis (severe reduction in white blood cells)
- Acute kidney inflammation (glomerulonephritis)
- Paralytic ileus (intestinal obstruction)
Additional side effects that have been reported include weight loss and enlargement of both the liver and spleen (hepatosplenomegaly), which is more common in association with SLE-like symptoms. Acute kidney failure has also been reported.
How Should You Store Apresolin?
Store Apresolin at or below 30°C (86°F) in the original container. Keep away from moisture. Do not use the medicine after the expiry date printed on the packaging. Keep out of the sight and reach of children.
Proper storage of Apresolin is essential to maintain the effectiveness and safety of the medication. Hydralazine is sensitive to moisture and heat, so following storage guidelines is important:
- Temperature: Store at no more than 30°C (86°F). Avoid exposing the tablets to excessive heat or direct sunlight.
- Moisture protection: Apresolin is moisture-sensitive. Keep the tablets in the original HDPE container with the lid tightly closed. Do not transfer tablets to another container.
- Expiry date: Do not use Apresolin after the expiry date stated on the packaging. The expiry date refers to the last day of the stated month.
- Keep out of reach of children: Store the medication in a safe place, out of the sight and reach of children.
- Disposal: Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines no longer in use. These measures help protect the environment.
What Does Apresolin Contain?
Each Apresolin tablet contains 25 mg of hydralazine hydrochloride as the active ingredient, along with several inactive excipients. The tablets are pale yellow, round, and biconvex in shape.
Active substance: Hydralazine hydrochloride 25 mg per tablet.
Inactive ingredients (excipients):
- Maize starch
- Microcrystalline cellulose
- Anhydrous colloidal silicon dioxide
- Povidone
- Magnesium stearate
- Copovidone
- Hypromellose
- Macrogol
- Talc
- Sucrose
- Iron oxide (E 172)
- Titanium dioxide (E 171)
Appearance: Apresolin tablets are pale yellow, round, and biconvex (slightly convex on both sides). They are supplied in HDPE (high-density polyethylene) containers holding 100 tablets.
Marketing Authorization Holder: Amdipharm Limited, Dublin 9, Ireland.
Manufacturer: Rottendorf Pharma GmbH, Ennigerloh, Germany.
How Does Apresolin Work in the Body?
Apresolin (hydralazine) works by directly relaxing the smooth muscle in arteriole walls, causing these small arteries to widen (vasodilate). This reduces peripheral vascular resistance, lowering blood pressure and decreasing the workload on the heart.
The mechanism of action of hydralazine involves a direct effect on vascular smooth muscle cells. Although the precise molecular mechanism is not fully understood, research suggests that hydralazine interferes with calcium release and movement within vascular smooth muscle cells, which is essential for muscle contraction. By inhibiting this process, the drug causes relaxation of the smooth muscle and subsequent vasodilation.
Importantly, hydralazine primarily affects arterioles (small resistance arteries) rather than veins. This selectivity means it predominantly reduces afterload (the resistance the heart must pump against) without significantly affecting preload (the blood returning to the heart through the veins). This characteristic makes it particularly useful in heart failure, where reducing afterload can substantially improve cardiac output.
The vasodilation caused by hydralazine triggers several compensatory reflex responses by the body, including:
- Reflex tachycardia: The drop in blood pressure activates the baroreceptor reflex, causing the heart rate to increase. This is why beta-blockers are often prescribed alongside Apresolin — to counteract this unwanted increase in heart rate.
- Increased renin release: The reduced renal perfusion pressure stimulates renin secretion, which can lead to sodium and water retention. This is why diuretics are often combined with hydralazine to counteract fluid retention.
- Increased cardiac output: The combination of reduced afterload and reflex sympathetic stimulation typically results in increased cardiac output, which can be beneficial in heart failure but may be problematic in patients with coronary artery disease.
Metabolism and acetylator status: Hydralazine is extensively metabolized in the liver through a process called acetylation. The rate of this metabolism varies between individuals depending on their genetic acetylator phenotype. Slow acetylators break down hydralazine more slowly, resulting in higher blood levels of the drug, which may increase both the therapeutic effects and the risk of side effects, particularly the development of drug-induced lupus-like syndrome. Fast acetylators may require higher doses to achieve the same therapeutic effect.
Hydralazine is rapidly absorbed from the gastrointestinal tract, with peak blood concentrations typically reached within 1–2 hours after oral administration. The duration of the antihypertensive effect is generally 6–8 hours, which is why the medication is usually administered in divided doses throughout the day.
Frequently Asked Questions About Apresolin
Apresolin (hydralazine) is a prescription medication used to treat high blood pressure (hypertension) and heart failure. It works as a direct-acting vasodilator, relaxing the smooth muscle in arteriole walls to reduce blood pressure and decrease the workload on the heart. It is typically prescribed when standard first-line treatments have not provided adequate results, and is usually used in combination with other medications such as beta-blockers and diuretics.
Yes, one of the notable side effects of Apresolin is the potential to cause a drug-induced lupus erythematosus-like syndrome (SLE-like syndrome). This occurs in up to 1 in 10 patients and is characterized by symptoms including joint pain, fever, skin rash, weakness, and shortness of breath. The risk increases with higher doses (particularly above 200 mg daily), prolonged treatment, and in patients who are genetically slow acetylators. The condition is generally reversible when Apresolin is discontinued, though recovery may take weeks to months.
No adverse fetal effects have been demonstrated with hydralazine, and it is considered one of the safer antihypertensive options during pregnancy. It has been used for decades to manage severe hypertension and pre-eclampsia in pregnant women, particularly when intravenous administration is needed. However, always consult your doctor before taking any medication during pregnancy, as all treatment decisions must weigh the benefits against potential risks for both mother and baby.
If you miss a dose of Apresolin, take it as soon as you remember. However, if it is nearly time for your next scheduled dose, skip the missed dose and continue with your regular schedule. Never take a double dose to compensate for a forgotten one, as this could cause your blood pressure to drop too low, leading to dizziness, fainting, or other complications. If you frequently forget doses, consider setting a reminder or using a pill organizer.
It is advisable to limit or avoid alcohol while taking Apresolin. Alcohol can enhance the blood pressure-lowering effect of hydralazine, potentially causing symptoms such as dizziness, lightheadedness, fainting, and increased heart rate. If you choose to drink, do so in moderation and be attentive to how the combination affects you. Always discuss alcohol consumption with your healthcare provider, especially if you are taking multiple medications.
Acetylator status refers to the speed at which your body metabolizes (breaks down) certain drugs through a process called acetylation in the liver. People are genetically classified as either "slow acetylators" or "fast acetylators." Slow acetylators process hydralazine more slowly, resulting in higher drug levels in the blood, which increases the risk of side effects, particularly the drug-induced lupus-like syndrome. Fast acetylators may need higher doses for the same therapeutic effect. Your doctor may take your acetylator status into consideration when determining your optimal dose.
References
This article is based on the following international medical guidelines, peer-reviewed research, and pharmacological references:
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List, 2023. Geneva: WHO; 2023. Hydralazine is listed as an essential medicine for cardiovascular diseases.
- McDonagh TA, Metra M, Adamo M, et al. 2023 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. European Heart Journal. 2023;44(37):3627-3639. doi:10.1093/eurheartj/ehad195
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. Journal of the American College of Cardiology. 2018;71(19):e127-e248. doi:10.1016/j.jacc.2017.11.006
- British National Formulary (BNF). Hydralazine hydrochloride. NICE Evidence Services. Available at: bnf.nice.org.uk. Accessed January 2026.
- Kandler MR, Mah GT, Tejani AM, Stabler SN, Salzwedel DM. Hydralazine for essential hypertension. Cochrane Database of Systematic Reviews. 2011;(11):CD004934. doi:10.1002/14651858.CD004934.pub4
- Taylor AL, Ziesche S, Yancy C, et al. Combination of isosorbide dinitrate and hydralazine in blacks with heart failure. New England Journal of Medicine. 2004;351(20):2049-2057. doi:10.1056/NEJMoa042934 (A-HeFT Trial)
- Rubin RL. Drug-induced lupus. Expert Opinion on Drug Safety. 2015;14(3):361-378. doi:10.1517/14740338.2015.995089
- European Medicines Agency (EMA). Summary of Product Characteristics: Hydralazine. London: EMA; updated 2025.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, a multidisciplinary group of licensed healthcare professionals specializing in cardiology, clinical pharmacology, and evidence-based medicine.