Known brand names include Trandate.
A beta blocker that also blocks alpha receptors, so it relaxes blood vessels and keeps the heart from speeding up. Tablets treat high blood pressure, and the IV form is given for severe high blood pressure.
Labetalol blocks two kinds of receptors that respond to adrenaline and similar stress chemicals. Blocking alpha-1 receptors lets blood vessels relax, which lowers the resistance the heart pumps against. Blocking beta receptors keeps the heart from racing during exercise or stress. Together these effects lower blood pressure without setting off a fast pulse, and the resting heart rate drops only a little.
Taken by mouth, it reaches its peak effect within 2 to 4 hours, and one dose lasts at least 8 hours, longer with bigger doses. Given by IV, each injection reaches its full effect within about 5 minutes. Because of the alpha-1 blocking, blood pressure falls more when standing than lying down, so people can feel dizzy or faint when they get up, most of all after an IV dose. The beta blocking can also slow the heart too much, tighten the airways in people with lung disease, and hide the racing heartbeat that warns of low blood sugar.
Labetalol treats high blood pressure. Pressure that stays high raises the chance of heart and blood vessel disease, and the risk grows faster the higher the pressure climbs. Bringing it down lowers the risk of strokes and heart attacks, including fatal ones. The tablets treat ongoing high blood pressure, and the IV form treats severe high blood pressure.
The tablets are taken by mouth, either alone or with other blood pressure medicines, especially water pills. The IV form is given into a vein as repeated injections or a slow drip, and people are then switched to the tablets. It controls high blood pressure without curing it, so the tablets are kept up even when people feel well. It has not been shown safe and effective in children, and it is not used by people with asthma or other airway disease that blocks airflow.
Dizziness, tiredness, nausea, indigestion, headache, and a stuffy nose are the most common complaints with the tablets. After an IV dose, more than half of people get dizzy or lightheaded if they sit up or stand too soon, and some notice nausea, sweating, or a tingling scalp. The label treats a very slow heartbeat or heart block, worsening heart failure, chest pain or a heart attack after stopping suddenly, and airway spasm as serious. Rare but severe liver injury and serious allergic reactions can also occur, and the usual warning signs of low blood sugar may be hidden.
A clinician may order these while someone is taking it.