biology

Hydralazine

Hydralazine is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hydralazine rather than just read about it. In short: Hydralazine, sold under the brand name Apresoline among others, is a medication used to treat high blood pressure and heart failure. This includes high blood pressure in pregnancy and very high blood pressure resulting in symptoms.

Key takeaways

Hydralazine belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hydralazine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hydralazine from memory before moving on to harder problems.

Reference excerpt

Hydralazine, sold under the brand name Apresoline among others, is a medication used to treat high blood pressure and heart failure. This includes high blood pressure in pregnancy and very high blood pressure resulting in symptoms. It has been found to be particularly useful in heart failure, together with isosorbide dinitrate, for treatment of people of African descent. It is given by mouth or by injection into a vein. Effects usually begin around 15 minutes and last up to six hours. Common side effects include headache and fast heart rate. It is not recommended in people with coronary artery disease or in those with rheumatic heart disease that affects the mitral valve. In those with kidney disease a low dose is recommended. Hydralazine is in the vasodilator family of medications, so it is believed to work by causing the dilation of blood vessels. Hydralazine was discovered while scientists at Ciba were looking for a treatment for malaria. It was patented in 1949. It is on the World Health Organization's List of Essential Medicines. In 2023, it was the 109th most commonly prescribed medication in the United States, with more than 6 million prescriptions.

Medical use Hydralazine is not used as a primary drug for treating hypertension because it elicits a reflex sympathetic stimulation of the heart (the baroreceptor reflex). The sympathetic stimulation may increase heart rate and cardiac output, and in people with coronary artery disease may cause angina pectoris or myocardial infarction. Hydralazine may also increase plasma renin concentration, resulting in fluid retention. To prevent these undesirable side effects, hydralazine is usually prescribed in combination with a beta blocker (e.g., propranolol) and a diuretic. Hydralazine is used to treat severe hypertension, but is not a first-line therapy for essential hypertension. Hydralazine is often used to treat hypertension in pregnancy together with either labetalol and/or methyldopa. Hydralazine is commonly used in combination with isosorbide dinitrate for the treatment of congestive heart failure in black populations. This preparation, isosorbide dinitrate/hydralazine, was the first race-based prescription drug. It should not be used in people who have tachycardia, heart failure, constrictive pericarditis, lupus, a dissecting aortic aneurysm, or porphyria.

Adverse effects Prolonged treatment may cause a syndrome similar to lupus, which can become fatal if the symptoms are not noticed and drug treatment stopped. Hydralazine is within the top three drugs that is known to induce systemic lupus and this adverse drug event is dose dependent yet significant. Very common (>10% frequency) side effects include headache, tachycardia, and palpitations. Common (1–10% frequency) side effects include flushing, hypotension, anginal symptoms, aching or swelling joints, muscle aches, positive tests for atrial natriuretic peptide, stomach upset, diarrhea, nausea and vomiting, and swelling (sodium and water retention).

Interactions Hydralazine may potentiate the antihypertensive effects of:

Drugs subject to a strong first-pass effect, such as beta blockers, may increase the bioavailability of hydralazine. The heart rate-accelerating effects of epinephrine (adrenaline) are increased by hydralazine, and coadministration may lead to toxicity.

Mechanism of action Hydralazine is a direct-acting smooth muscle relaxant and acts as a vasodilator primarily in resistance arterioles, also known as the smooth muscle of the arterial bed. The molecular mechanism involves inhibition of inositol trisphosphate-induced Ca2+ release from the sarcoplasmic reticulum in arterial smooth muscle cells. By relaxing vascular smooth muscle, vasodilators act to decrease peripheral resistance, thereby lowering blood pressure and decreasing afterload. The exact mechanism of action of hydralazine is unknown, at least as of 1981. Metabolic products include the N-acetyl derivative, pyruvic acid hydrazone, and acetone hydrazone, each of which may also contribute to reducing blood pressure.

Chemistry Hydralazine belongs to the hydrazinophthalazine class of drugs.

History The antihypertensive activity of hydralazine was discovered by scientists at Ciba, who were trying to discover drugs to treat malaria; it was initially called C-5968 and 1-hydrazinophthalazine; Ciba's patent application was filed in 1945 and issued in 1949, and the first scientific publications of its blood pressure-lowering activities appeared in 1950. It was approved by the FDA in 1953. It was one of the first antihypertensive medications that could be taken by mouth.

Research Hydralazine has also been studied as a treatment for myelodysplastic syndrome in its capacity as a DNA methyltransferase inhibitor.

References

Illustrations

Worked examples

Example 1 — a first encounter with Hydralazine

Start with the simplest possible case. Write down what Hydralazine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hydralazine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hydralazine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hydralazine

In research: Hydralazine appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hydralazine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hydralazine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antihypertensive agents, Drugs with unknown mechanisms of action, Hepatotoxins, so understanding it makes those chapters shorter.
In everyday life: Look for Hydralazine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Hydralazine” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Hydralazine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hydralazine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hydralazine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hydralazine in simple terms?

Why does Hydralazine matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hydralazine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hydralazine.