A blood vessel relaxer that lowers blood pressure by acting directly on the muscle in artery walls. Tablets treat essential high blood pressure, and the injection is for severe high blood pressure when pills cannot be taken or pressure must come down quickly.
Hydralazine relaxes the smooth muscle in the walls of the small arteries, which widens them so blood flows more easily. It seems to work by changing how calcium moves inside these muscle cells, though the exact way it works is not fully known. It widens arteries more than veins, so blood pressure falls, the lower number more than the upper one. In response, the heart beats faster and pumps more blood, and hormone signals lead the kidneys to hold on to more salt.
Taken by mouth, it is absorbed quickly and reaches its highest blood level in 1 to 2 hours, while after an injection blood pressure can start to fall within minutes. People may notice a pounding or fast heartbeat, headache, or flushing as the blood vessels widen. The extra work for the heart can bring on chest pain or, rarely, a heart attack in people with blocked heart arteries. Some people clear it slowly and end up with higher blood levels, and large doses make a lupus-like immune reaction more likely.
Hydralazine treats high blood pressure. Left untreated, high blood pressure can damage the brain, heart, blood vessels, and kidneys, leading to heart attack, stroke, heart failure, kidney failure, or vision loss. The tablets are used for long-term control, either alone or added to other blood pressure medicines. The injection is kept for severe high blood pressure when the drug cannot be swallowed or the pressure must come down urgently.
The tablets are taken by mouth with meals or a snack, often along with a low-salt diet. The injection is given into a vein or a muscle in the hospital, and most people move to tablets within 24 to 48 hours. It controls blood pressure without curing it, so it is kept up even when people feel well. It is not used by people with coronary artery disease or rheumatic disease of the mitral heart valve, and controlled studies have not shown it safe and effective in children.
Headache, a fast or pounding heartbeat, loss of appetite, nausea, vomiting, and diarrhea are the most common effects, and some people notice flushing, a stuffy nose, or watery eyes. The label treats chest pain and heart attack in people with heart artery disease as serious, along with a lupus-like illness that can bring joint pain, fever, and kidney inflammation. Numbness and tingling in the hands and feet, low blood counts, and low blood pressure with fainting can also occur.