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.
Adalat 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 lower 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 in the management of 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.
Adalat retard tablets are a ‘long-acting’ or ‘modified-release’ form of nifedipine. They are designed to release the nifedipine slowly and continuously over 12 hours. This produces a steady blood level of the medicine throughout the day.
How do I take it?
- Adalat retard tablets in Kenya are designed to be taken twice a day (every 12 hours). The dose prescribed will depend on the condition being treated. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label your pharmacist has put on the packet of medicine.
- Adalat retard tablets should be swallowed whole with a drink of water. The tablets should not be not broken, chewed or crushed, as this can damage the modified-release action. They can be taken with or without food.
- You should not drink grapefruit juice while you are taking this medicine, as it can increase the level of nifedipine in your blood and thus increase the chance of getting side effects.
- Blood pressure lowering medicines can occasionally make you feel dizzy or weary. If you are affected, you should take care 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.
- This medicine should not be used to treat an attack of angina, as it won’t work quickly enough.
- There are several different brands of long-acting or slow-release nifedipine available in the Kenya (see end of factsheet). These can usually be identified because their names end in XL, MR, LA, SR and so on. The way that the nifedipine is released from different brands can vary and this means that different brands can have different clinical effects. For this reason, it is important that you always take the same brand of nifedipine. You should make sure you know which brand you take and check that you have been given the correct one each time your medicine is dispensed. (Your Kenyan pharmacist will usually ask you, or call your doctor, if this is not written on your prescription).
Use with caution in
- Elderly people.
- Decreased liver function.
- People having kidney dialysis.
- Heart failure.
- People with poor functioning of one chamber of the heart (left ventricular dysfunction).
- People with very low blood pressure (hypotension).
- Hereditary blood disorders called porphyrias.
Not to be used in
- Allergy to related calcium channel blockers (dihydropyridines), eg amlodipine, felodipine, nicardipine.
- Angina that is increasing in severity, duration or frequency and is not well controlled by medical treatment (unstable angina).
- People with a condition called aortic stenosis, which is narrowing of the main artery from the heart through which blood is pumped to the rest of the body.
- Failure of the heart to maintain adequate circulation of blood (cardiogenic shock).
- People who are having a heart attack or who have had a heart attack in the last month.
- This medicine is not recommended for children.
- Adalat retard tablets contain lactose and are not suitable for people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption.
This medicine should not be used if you are allergic to 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. The manufacturer states that it should not be used before week 20 of pregnancy. 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 be used by breastfeeding mothers. Seek medical advice from your doctor.
- This medication is to be swallowed whole, not chewed.
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. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.
Common (affect between 1 in 10 and 1 in 100 people) side effects of Adalat 20mg in Kenya
- Headache (this usually improves after a few days of treatment).
- Flushing (this usually improves after a few days of treatment).
- Swollen ankles caused by fluid retention (peripheral oedema).
- Feeling weak or tired.
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Disturbances of the gut such as nausea, indigestion, abdominal pain, flatulence.
- Low blood pressure.
- Awareness of your heart beat (heart palpitations).
- Increased heart rate (tachycardia).
- Nasal congestion.
- Problems with sleeping.
- Vertigo (spinning sensation).
- Shaking, usually of the hands (tremor).
- Increased need to pass urine.
- Impotence (erectile dysfunction).
- Swollen joints.
- Visual disturbances.
Rare (affect between 1 in 1000 and 1 in 10,000 people)
- Pins and needles sensations (paraesthesia).
- Skin reactions such as itching, rash, hive like rash.
- Enlargement of the gums (gingival hyperplasia).
- Shortness of breath.
- Yellowing of the skin and eyes (jaundice).
- Raised blood sugar levels (hyperglycaemia).
- Decrease in the number of white blood cells in the blood (leucopenia).
- Pain in the muscles or joints.
- Red or purple areas of skin discolouration caused by bleeding under the skin (purpura).
The side effects listed above may not include all of the side effects reported by the medicine’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?
It is important to 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 ask your doctor or pharmacist before taking any new medicines during treatment with this one, to check that the combination is safe.
The antibiotic rifampicin should not be used with this medicine, as it decreases the blood level of nifedipine and could make it less effective.
If nifedipine is used in combination with other medicines that lower blood pressure, either to treat high blood pressure (antihypertensives), or as a side effect, the combination might lower your blood pressure too much. This could make you feel dizzy or faint, particularly when moving from a lying or sitting position to sitting or standing. This is more likely when you first start taking nifedipine with one of these medicines. If this happens to you, you should sit or lie down until the symptoms pass. Tell your doctor if any dizziness persists, as your medicine doses may need adjusting. Other medicines that decrease blood pressure include the following:
- ACE inhibitors, eg enalapril
- alpha-blockers such as prazosin
- angiotensin II receptor antagonists such as losartan
- benzodiazepines, eg temazepam, diazepam
- beta-blockers such as propranolol
- other calcium-channel blockers, eg verapamil, felodipine
- diuretics, eg furosemide, bendroflumethiazide
- dopamine agonists, eg bromocriptine, apomorphine
- MAOI antidepressants, eg phenelzine
- nitrates, eg glyceryl trinitrate
The following medicines may decrease the breakdown of nifedipine by the liver, which could increase the risk of its side effects:
- protease inhibitors for HIV infection, eg ritonavir, nelfinavir, saquinavir
If you take any of these with nifedipine in Kenya, you should tell your doctor if you feel dizzy or experience any other side effects, as the dose of your nifedipine may need to be reduced.
The following medicines may increase the breakdown of nifedipine by the liver and could therefore make it less effective. If you take any of these in combination with nifedipine your doctor may need to increase your nifedipine dose:
- the herbal remedy St John’s wort (Hypericum perforatum).
If nifedipine is taken in combination with diltiazem, the blood level of both medicines may increase and their doses may need to be adjusted.
If nifedipine 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 decrease the breakdown of the following medicines by the liver and may therefore increase the amount of these medicines in the blood. As this could increase the risk of their side effects, your doctor may need to prescribe a lower dose of these medicines if you take them in combination with nifedipine:
The following medicines may reduce the blood pressure lowering effect of this medicine:
- corticosteroids, such as dexamethasone or prednisolone
- oestrogens, such as those in the contraceptive pill
- regular use of non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac or indomethacin (occasional painkilling doses are unlikely to have a significant effect).
Other medicines containing the same active ingredient available in Kenya
- Adalat LA
- Depin-E Retard
- Cardia Retard
- Nepif Retard
- Zenusin SR
Short-acting nifedipine capsules are also available without a brand name, ie as the generic medicine.