Hydralazine
Trade name Apresoline
Routes of administration are oral, and intravenous.
Bioavailability is 26-50%.
Protein binding is 85-90%.
Hepatic metabolism.
Biological half-life 2-8 hours, 7-16 hours in those with renal impairment.
Excretion by kidneys.
A direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles.
By relaxing vascular smooth muscle, vasodilators act to decrease peripheral resistance, thereby lowering blood pressure and decreasing afterload.
Has a short term effect on blood pressure, as the system will reset to the previous, high blood pressure.
Belongs to the hydrazinophthalazine class of drugs.
Hydralazine is not used as a primary drug for treating hypertension because it elicits a reflex sympathetic stimulation of the heart.
Sympathetic stimulation may increase heart rate and cardiac output.
In patients with coronary artery disease the drug may cause angina pectoris or myocardial infarction.
May increase plasma renin concentration, resulting in fluid retention.
To prevent undesirable side effects, it is usually prescribed in combination with a beta-blocker and a diuretic.
Not a first-line therapy for essential hypertension.
First-line therapy for hypertension in pregnancy
Used successfully as a treatment for myelodysplastic syndrome in its capacity as a DNA methyltransferase inhibitor.
Commonly used in combination with isosorbide dinitrate for the treatment of congestive heart failure in African Americans
Common side effects include:
Headache
High heart rate
Palpitations
Flushing
Hypotension
Anginal symptoms
Joint pains
Positive test for ANA
Gastrointestinal disturbances
Joint swelling
Muscle aches
Edema
Relatively contraindicated in systemic lupus erythematosus and related diseases.
Severe tachycardia and heart failure with a high cardiac output.
Myocardial insufficiency due to mechanical obstruction in the presence of aortic or mitral stenosis or constrictive pericarditis.
Isolated right-ventricular heart failure due to pulmonary hypertension.
Dissecting aortic aneurysm
It may potentiate the antihypertensive effects of: Vasodilators, calcium antagonists, ACE inhibitors, diuretics, antihypertensives, tricyclic antidepressants, major tranquillizers, and alcohol.
Beta-blockers may increase the bioavailability of hydralazine.
Epinephrine heart rate-accelerating effects are increased by hydralazine, hence may lead to toxicity.
Hydralazine causes arterial vasodilation.
Hydralazine requires the endothelium to provide nitric oxide, thus only causes vasodilation in vivo with functional endothelium.
The onset of hydralazine induced systemic lupus is slow and takes at least 3-6 months with the usual range of 9 to 40 months.
Musculoskeletal symptoms are the most common clinical manifestation with arthritis of the hands and wrists for hydralazine induced SLE.
Laboratory tests for the diagnosis of hydralazine induced lupus includes positive ANA, antihistamine antibodies and a positive test for rheumatoid factor.
Antihistone antibodies havea high sensitive sensitivity of up to 90% in hydralazine induced lupus erythematosus.