© Ben Huczek 2005

Nifedipine

Main Use

Active Ingredient

Manufacturer

High blood pressure, Angina

Nifedipine.

Non-proprietary

How does it work?

This medicine contains the active ingredient nifedipine, which is a type of medicine called a calcium channel blocker. This type of medicine acts on the heart and blood vessels.

Nifedipine works by slowing the movement of calcium through the muscle cells that are found in the walls of blood vessels. It does this by blocking 'calcium channels' in these muscle cells. Calcium is needed by muscle cells in order for them to contract, so by depriving them of calcium, nifedipine causes the muscle cells to relax.

Nifedipine acts specifically on the muscle cells in the walls of arteries, causing them to relax. This allows the arteries in the body to widen, an effect that has two main uses.

The relaxing and widening of the small arteries in the body decreases the resistance that the heart has to push against in order to pump the blood around the body. This reduces the pressure within the blood vessels. Nifedipine can therefore be used to treat high blood pressure.

The widening effect on the small arteries and the arteries in the heart also improves the blood and therefore oxygen supply to the heart. This feature means nifedipine can be used to treat angina. The chest pain of angina is caused by insufficient oxygen supply to the heart. As nifedipine improves this oxygen supply, and also reduces the effort the heart has to make to pump blood, it is used to prevent angina attacks.

Nifedipine is also sometimes used to treat a circulatory disorder called Raynaud's phenomenon. In this condition the blood vessels in the hands go into spasm and contract excessively when the hands are cold. This causes the hands to go white, numb and painful. Nifedipine relaxes the peripheral arteries in the hands, causing them to widen and the blood circulation to the fingers to improve.

Nifedipine may be given in a form that has an effect as soon as the medicine is taken and then tapers off (described as immediate-release or short-acting), or in a form that releases the medicine slowly over the day (which may be described as controlled/slow/prolonged/extended/modified/sustained-release or long-acting).

Short-acting nifedipine is usually used for the short-term control of high blood pressure and to relieve the symptoms of Raynaud's.

There are many different brands of slow-release nifedipine available, and these can usually be identified because their names end in XL, MR, LA, SR and so on. Long-acting nifedipine is usually used for the long-term treatment of high blood pressure and prevention of angina. If you are prescribed long-acting nifedipine it is important that you know what brand you are taking, and that you always take the same brand, as different brands do not release the nifedipine in the same way and so can have different clinical effects.
 

What is it used for?
 

  • Warning!
     
    • Different brands of modified-release or long-acting preparations of this medicine may not have the same clinical effect. Try to remember what brand you are taking and make sure you have the correct medicine by checking with your doctor or pharmacist if the medicine you are given looks different from your usual one.
       
    • Dizziness and weariness may occasionally occur during treatment with blood pressure lowering medicines. If you are affected, caution is required when driving or operating machinery.
       
    • If you experience any chest pain after taking this medicine you should not take a further dose until you have consulted your doctor.
       
    • You should avoid drinking grapefruit juice while taking this medicine, as it can increase the level of the medicine in your blood. This effect of grapefruit juice can last for at least three days after you drink it.
       
  • Use with caution in
     
  • Not to be used in
     
  • This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

    If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
     
  • Pregnancy and Breastfeeding

    Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
     

    • This medicine should not normally be used during pregnancy as its safety has not been established. However, it is occasionally used to control high blood pressure in pregnant women, in which case any possible risk to the foetus from the medicine needs to be weighed against the possible risk of uncontrolled high blood pressure in the mother. Seek medical advice from your doctor.
       
    • This medicine passes into breast milk in amounts that are probably too small to be harmful to the nursing infant. However, since the medicine does pass into breast milk, the manufacturer recommends that it should not used by breastfeeding mothers. Seek medical advice from your doctor.
       
  • Side effects

    Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
     
    • Depression
       
    • Impotence
       
    • Shaking, usually of the hands (tremor)
       
    • Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain
       
    • Awareness of your heart beat (heart palpitations)
       
    • Visual disturbances
       
    • Abnormal enlargement of breasts in men (gynaecomastia)
       
    • Increased need to pass urine
       
    • Pins and needles (paraesthesia)
       
    • Dizziness
       
    • Flushing
       
    • Pain in the muscles (myalgia)
       
    • Excessive fluid retention in the body tissues, resulting in swelling (oedema)
       
    • Groupings of fine blood vessels becoming prominent under the skin (telangiectasia)
       
    • Skin reactions such as rash and itch
       
    • Enlargement of the gums (gingival hyperplasia)
       
    • Increased heart rate (tachycardia)
       
    • Headache
       
    • Tiredness
       
  • The side effects listed above may not include all of the side effects reported by the drug's manufacturer.

    For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
     
  • How can this medicine affect other medicines?

    Tell your doctor or pharmacist what medicines you are taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Likewise, always check with your doctor or pharmacist before taking any new medicines during treatment with this one.

    If nifedipine is taken in combination with other medicines that are used to lower blood pressure, for example beta-blockers, alpha-blockers, ACE inhibitors, diuretics, there will be an enhanced blood pressure lowering effect. This may also occur if nifedipine is taken with medicines that can reduce blood pressure as a side effect, for example antipsychotic medicines. The drop in blood pressure may sometimes cause dizziness or lightheadedness, particularly when moving from a lying or sitting position to sitting or standing. This is more likely when you first start taking this medicine. If affected you should sit or lie down until the symptoms pass. Consult your doctor if dizziness persists, as your medicine doses may need adjusting.

    The antibiotic rifampicin should not be used with this medicine, as it decreases the blood level of nifedipine and could make it less effective.

    The blood level of nifedipine may be reduced by the antiepileptic medicines phenytoin and phenobarbital.

    The blood level of nifedipine may be increased by the following medicines:
    - cimetidine
    - itraconazole
    - fluconazole.
    If you take any of these with this medicine, your doctor may need to reduce the dose of your nifedipine.

    If this medicine is taken in combination with diltiazem, the blood level of both medicines may increase and their doses may need to be adjusted.

    If this medicine is taken in combination with quinidine, the blood level of quinidine may increase or decrease, and the blood level of nifedipine may increase. Your doctor may need to alter the dose of either medicine.

    Nifedipine may increase blood levels of the following medicines:
    - digoxin
    - phenytoin
    - tacrolimus
    - theophylline.