Labetalol belongs to a class of medications called beta-blockers. It is used to treat high blood pressure. It helps to decrease blood pressure by reducing the workload on the heart and by opening the blood vessels.

Labetalol may be used alone, but is often used in combination with additional high blood pressure medications called diuretics (water pills). The injectable form of labetalol is used for emergency treatment of severe high blood pressure.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

[Tablet forms only]

The recommended starting dose of labetalol is 100 mg taken by mouth, 2 times daily after food. Your doctor may adjust the dose of the medication once or twice a week according to your needs and response to the medication. The usual maintenance dose ranges from 200 mg to 400 mg by mouth twice daily. The maximum recommended dose is 600 mg by mouth twice daily.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is within 8 hours of your next dose, skip the missed dose and continue on with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Do not stop taking this medication suddenly without checking with your doctor first. Stopping the medication suddenly after you have been taking it for a while may cause unpleasant and potentially harmful effects.

Store this medication at room temperature and keep it out of the reach of children.

Each mL contains 5 mg of labetalol HCl. Nonmedicinal ingredients: dextrose anhydrous, disodium edetate, methylparaben, propylparaben, anhydrous citric acid and/or sodium hydroxide to adjust pH, and water for injection.

Do not take this medication if you:

• are allergic to labetalol or any ingredients of the medication
• are experiencing cardiogenic shock with very low blood pressure
• have a severely slow heart rate
• have asthma or a history of obstructive airway disease such as emphysema or chronic bronchitis
• have serious heart block
• have uncontrolled congestive heart failure
• have severely decreased blood flow in your feet and your legs (peripheral artery disease)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness
• headache
• nausea
• unusual tiredness
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• breathing difficulty or wheezing
• dizziness or lightheadedness when getting up from a lying down or sitting position
• joint or muscle pain
• signs of heart problems (e.g., fast, irregular heartbeat or pulse, chest pain, sudden weight gain, difficulty breathing, leg swelling)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• slow heartbeat (especially less than 50 beats per minute)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• chest pain
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Breathing conditions: In general, people who have asthma and certain other breathing problems should avoid taking a beta-blocker such as labetalol, as this group of medications can cause breathing difficulty. If you have breathing problems and your doctor has prescribed labetalol for you, it may be at a lower dose, and your doctor will monitor you regularly while you are taking this medication. If you have breathing problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Diabetes: The signs of low blood sugar may not be as noticeable when taking labetalol. If you have diabetes and take insulin or other medications that work by reducing the blood sugar, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Dizziness: Move slowly when moving from a lying down or sitting position to a standing position as dizziness may occur, especially when this medication is first being started.

Dry eyes: Dry eyes have been reported with the use of this medication.

Heart disease: Beta-blockers, such as labetalol, can worsen existing heart failure. It is important to take labetalol exactly as prescribed by your doctor to decrease the chance of this happening. If you have a history of heart disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Hyperthyroidism (high level of thyroid hormones): Labetalol may reduce the symptoms of hyperthyroidism and give a false impression of improvement. Stopping labetalol suddenly could cause hyperthyroidism to become worse. If you have a history of thyroid disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

Rarely, liver injury has been reported with the use of this medication. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Pheochromocytoma: Although labetalol is used to treat the high blood pressure that is a symptom of pheochromocytoma (a tumour of the adrenal gland), it has been known to worsen the symptoms it is supposed to be treating. If you have a pheochromocytoma, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Severe allergies: If you have allergies severe enough to cause anaphylaxis (a severe allergic reaction where swelling of the face, lips, and throat make it difficult to breathe), discuss with your doctor what to do if you have an allergic reaction. Labetalol, like other beta-blockers, may make it more difficult to treat severe allergic reactions with epinephrine.

Skin conditions: Various skin rashes have been reported with the use of this medication.

Stopping the medication: This medication should not be stopped suddenly. People with heart disease who stop taking this medication abruptly may experience serious effects, such as severe worsening of angina, heart attack, or abnormal heart rhythms. If you have heart disease, do not stop taking this medication without checking with your doctor first. When this medication needs to be stopped, it should be done gradually, under the supervision of your doctor.

Surgery: If you are scheduled for surgery, inform all health care professionals involved in your care that you are taking labetalol.

Pregnancy: Labetalol should not be used during pregnancy unless the benefits outweigh the risk. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and are taking labetalol, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: Seniors may be more sensitive to the side effects of labetalol and may require lower doses.

There may be an interaction between labetalol and any of the following:

• aldesleukin
• aliskiren
• alpha-agonists (e.g., clonidine, methyldopa)
• alpha-blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• alpha/beta agonists (e.g., epinephrine, norepinephrine)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• angiotensin converting enzyme inhibitors (ACEIs; captopril, enalapril, ramipril)
• angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• beta-2 agonists (e.g., formoterol, salbutamol, salmeterol)
• brimonidine
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• ceritinib
• dexmethylphenidate
• digoxin
• dipyridamole
• disopyramide
• diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
• donepezil
• dronedarone
• duloxetine
• ergot alkaloids (e.g., ergotamine, dihydroergotamine)
• galantamine
• grass pollen allergen extract
• guanfacine
• insulin
• ivabradine
• lacosamide
• levodopa
• mefloquine
• methylphenidate
• minoxidil
• multiple sclerosis (MS) medications (e.g., fingolimod, ponesimod, ozanimod, siponimod)
• narcotic pain medications (e.g., fentanyl, hydromorphone, morphine)
• nitrates (e.g., nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
• non-steroidal anti-inflammatory medications (NSAIDs; e.g., diclofenac, ibuprofen, naproxen)
• obinutuzumab
• pentoxifylline
• phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pramipexole
• propafenone
• rasagiline
• rivastigmine
• ropinirole
• sacubitril
• somatostatin-like medications (e.g., lanreotide, octreotide, pasireotide)
• sulfonylureas (e.g., gliclazide, glyburide)
• theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
• tizanidine
• tofacitinib
• white birch allergen extract

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.