Nifedipine belongs to the class of medications called calcium channel blockers. It is used to treat high blood pressure and angina (chest pain brought on by exercise or stress). It works to control blood pressure and reduce the number of angina attacks by relaxing blood vessels. The immediate-acting form of nifedipine is also used to treat coronary spasm, the sudden constriction of the coronary artery in the heart.

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 taking this medication, speak to your doctor. Do not stop taking 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 take this medication if their doctor has not prescribed it.

The usual starting dose for treatment of high blood pressure is 20 mg to 30 mg of a long-acting formula of nifedipine (extended release tablets, XL tablets, or PA tablets) once daily. For the treatment of angina, the usual starting dose is 30 mg. The maximum recommended daily dose is 90 mg.

For the extended-release tablets, or XL tablets, the recommended doses range from 20 mg to 90 mg once daily.

For capsules (immediate-release form), the recommended doses range from 5 mg to 20 mg three or four times daily, to a maximum of 120 mg taken each day.

Nifedipine may be taken with or without food. The long-acting forms of the medication should be swallowed whole and should not be bitten, crushed, chewed or divided. Dosage is based on individual tolerance and response, and should be started at a low dose. Higher doses (e.g., 60 mg or 90 mg) are not recommended for initial treatment. Higher doses should be used for treatment once the dose has been stabilized.

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 almost time for your next dose, skip the missed dose and continue 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.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take nifedipine if you:

• are allergic to nifedipine or any ingredients of the medication
• are allergic to other drugs that are similar to nifedipine (dihydropyridine calcium antagonists) (e.g., amlodipine, felodipine)
• are breast-feeding
• are or may become pregnant
• have very low blood pressure or are in shock
• are in the period immediately following a heart attack (applies to the immediate-release form of nifedipine)
• have a Kock pouch (ileostomy after a proctocolectomy)
• are taking the medication rifampicin
• have a severe blockage in the digestive system
• have moderate to severe liver 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.

• anxiety
• decreased sexual ability
• dizziness or lightheadedness
• dry mouth
• headache
• leg cramps
• nausea
• nervousness
• trouble sleeping
• unusual tiredness or weakness
• upset stomach
• 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:

• abdominal cramps
• back pain
• breathing difficulty, coughing, or wheezing
• breast enlargement (men)
• chest tightness
• chest pain (may appear about 30 minutes after medication is taken)
• confusion
• constipation
• diarrhea
• dizziness when rising from a sitting or lying position
• enlarged gums
• eye pain
• fainting
• increased urination
• irregular or fast, pounding heartbeat
• menstrual changes
• muscle or joint pain
• rash
• 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)
• skin sensitivity to the sun
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• swelling of the ankles, feet, or lower legs
• tingling, burning, numbness, or pain in the hands, arms, feet, or legs

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

• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of heart attack (e.g., sudden chest pain or pain radiating to back, down arm, jaw; sensation of fullness of the chest; nausea; vomiting; sweating; anxiety)
• signs of intestinal blockage (e.g., swollen, hard or painful abdomen, vomiting and constipation)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort

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.

Diabetes: For people with diabetes, nifedipine may affect their control of blood sugar levels. If you have diabetes, 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. It may be necessary to check your blood sugar regularly until you know how this medication affects your blood sugar control.

Fertility: This medication may affect male fertility. Talk to your doctor if this is important to you.

Grapefruit juice: Grapefruit juice can increase blood levels of nifedipine. Avoid drinking grapefruit juice or eating grapefruit before or while you are taking nifedipine.

Heart attack: Immediate-release nifedipine should not be used within one week after a heart attack.

Heart failure: Rarely, nifedipine causes severely decreased blood pressure, making symptoms of heart failure worse for people with severe heart failure. If you have heart failure, 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.

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.

Low blood pressure: People prone to low blood pressure should monitor their blood pressure frequently while they are taking nifedipine. Blood pressure may occasionally drop more than expected when starting nifedipine. Be alert for any lightheadedness, dizziness, or a faster than normal heart rate. Move slowly when changing from a lying down to an upright position. If your blood pressure drops too low, your doctor will adjust your dose or try another medication.

Stomach disorders: People with certain stomach disorders (e.g., narrowing of the gastrointestinal tract) should talk with their doctor about the risks and benefits of taking this medication. If you have any stomach disorders, such as a narrowing of the gastrointestinal tract, 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.

Surgery: If you are scheduled for surgery, inform your doctor that you are taking this medication.

Pregnancy: This medication should not be taken by women who are or may become pregnant, as nifedipine may cause harm to the developing baby if it is taken by the mother during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking nifedipine, it may affect your baby. Women who are taking nifedipine are discouraged from breast-feeding. 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 nifedipine.

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

• alcohol
• aldesleukin
• alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
• anti-psychotics (e.g., cariprazine, clozapine, olanzapine, quetiapine, risperidone)
• apalutamide
• apomorphine
• aprepitant
• "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• barbiturates (e.g., butalbital, phenobarbital)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• bortezomib
• bosentan
• brimonidine
• bromocriptine
• other calcium channel blockers (e.g., diltiazem, verapamil)
• calcium supplements (e.g., calcium carbonate, calcium citrate)
• cimetidine
• clopidogrel
• cobicistat
• cyclosporine
• dantrolene
• digoxin
• dipyridamole
• diuretics (water pills; e.g., bumetanide, furosemide)
• dronedarone
• duloxetine
• enzalutamide
• flunarizine
• fluoxetine
• general anesthetics (medications used to put people to sleep before surgery)
• grapefruit juice
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., efavirenz, etravirine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir)
• letermovir
• levodopa
• lumacaftor and ivacaftor
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• magnesium supplements
• melatonin
• methylphenidate
• mifepristone
• mitotane
• modafinil
• monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, rasagiline, selegiline, tranylcypromine)
• morphine
• nabilone
• nitrates (e.g., nitroglycerin, isosorbide dinitrate)
• obinutuzumab
• pentoxifylline
• phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pramipexole
• primidone
• protein kinase inhibitors (e.g., ceritinib, crizotinib, imatinib)
• rifabutin
• rifampin
• riociguat
• ropinirole
• rotigotine
• sacubitril
• sodium phosphates
• St. John's wort
• seizure medications (e.g., carbamazepine, eslicarbazepine, phenytoin)
• tacrolimus
• theophylline
• tizanidine
• tretinoin
• tricyclic antidepressants (e.g., clomipramine, imipramine)
• vincristine
• yohimbine

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.