Active Ingredients

Dihydralazine – Effect, Application & Risks


Dihydralazine is an antihypertensive drug used to treat arterial hypertension . The exact molecular mode of action is not known. A major area of ​​application is blood pressure regulation in severe preeclampsia .

What is dihydralazine?

Dihydralazine is a pharmacological agent used to treat high arterial blood pressure . The active ingredient dilates the arteries and arterioles in smooth muscle , thereby lowering peripheral resistance to blood flow.

Dihydralazine is a solid composed of orange needles. It is available in Germany under the trade names Nepresol® and Depressan®. Nepresol® and Depressan® are medicines for lowering blood pressure and are used in particular in the case of severe high blood pressure.

The main area of ​​application is preeclampsia in patients with a pregnancy characterized by severe hypertension and edema .

Dihydralazine consists of an aromatic benzene ring connected to a hetero ring of carbon and nitrogen atoms. Two hydrazine groups are bonded in opposite positions to this hetero ring. The mechanism of action of dihydralazine is not yet known.

Pharmacological action

The pharmacological importance of dihydralazine is to dilate the arteries. Due to the reduced arterial resistance to blood flow, the blood pressure drops. The processes at the molecular level cannot yet be understood. In the organism, dihydralazine is metabolized in the liver .

The active ingredient is taken in the form of tablets or as a solution. Dihydralazine can also be administered intravenously. In this case, the effect occurs about 15 minutes after the infusion . The half-life in the body is 2.2 to 2.6 hours. The drug has a bioavailability of approximately 30 to 55 percent, which means that only 30 to 55 percent of the original drug can develop its effectiveness. This is due to the fact that the active substance dihydralazine is subject to a strong first-pass effect during its first passage through the liver .

During this first passage through the liver, a large part of the active substance is acetylated. In this case, a hydrogen atom on a functional group or a CH bond is replaced by an acyl group. The acylated molecules are excreted in the urine . Depending on the duration of the acetylation process, the drug’s effect lasts for around three to four hours. Because different people acetylate at different rates or slowly, the breakdown of the active ingredient varies from person to person.

Medical Application & Use

Because of its blood pressure lowering properties, dihydralazine is an antihypertensive drug . The term antihypertensive is a collective term for all blood pressure lowering drugs.

The increase in blood pressure, known as preeclampsia, can lead to kidney damage . However, as already mentioned, under the influence of dihydralazine, the arteries expand and the blood flow improves. As a result, blood pressure drops. Especially in the case of preeclampsia, it is the drug of first choice, since the active ingredient does not affect the blood flow through the uterus and placenta .

However, after the start of treatment, no child should be breastfed, since the active ingredient also passes into breast milk . Because the newborn’s liver is not yet fully mature, the active ingredient can only be broken down poorly there, causing dihydralazine to accumulate in the body.

In addition to its use to regulate blood pressure in pregnant women and young mothers, dihydralazine is also used to lower blood pressure in general. It is often used in combination with other medicines that lower blood pressure.

Risks & side effects

In principle, long-term oral therapy with dihydralazine would be possible. Due to the many side effects , however, the active ingredient is not suitable for such therapy.

For dihydralazine there are many contraindications, contraindications and side effects. These include a sudden drop in blood pressure , skin redness , gastrointestinal disorders , nausea , diarrhea , constipation or edema . In rare cases, depression , skin rashes with itching , changes in the blood picture or allergic reactions occur.

Even rarer are tingling or numbness in the limbs, muscle spasms , or liver dysfunction . Patients who are slow acetylators may experience rheumatism-like joint pain , swelling of the lymph glands , conjunctivitis , liver inflammation or urinary bladder inflammation .

Dihydralazine is contraindicated in hypersensitivity, lupus erythematosus (butterfly itch), an aorta aneurysm , or severe heart failure . For other heart problems , dihydralazine should never be taken alone, but in combination with beta-blockers .

In the case of renal insufficiency , liver diseases or circulatory disorders in the brain , dihydralazine must be used very carefully. Dihydralazine should not be used during the first trimester of pregnancy. There are also interactions with other medications that can lead to both weakening and strengthening the effect.

Constant medical checks are necessary during treatment with dihydralazine in order to be able to quickly identify any deviations. Reactivity can also be limited for up to a few hours after taking the drug.

Lisa Newlon
 | Website

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.