How does it work?

Prescal tablets contain the active ingredient isradipine, which is a type of medicine called a calcium-channel blocker.

Isradipine 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 so that they can contract. Isradipine reduces the amount of calcium available to muscle cells and so makes them relax.

Isradipine acts specifically on the muscle cells in the walls of arteries, causing them to relax. This allows the arteries in the body to widen.

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. Isradipine is therefore used to lower high blood pressure.

Isradipine can also have a widening effect on the small arteries in the heart, which improves the supply of blood, and therefore the oxygen to the heart. This reduces the effort the heart has to make to pump blood around the body.

What is it used for?

• High blood pressure (hypertension).

How do I take it?

• Prescal tablets are usually taken twice a day (every 12 hours). The tablets can be taken with or without food.
• The dose prescribed depends on your blood pressure measurements. 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.
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• You should not drink grapefruit juice while you are taking this medicine, as it can increase the level of isradipine in your blood and thus increase the chance of getting side effects.

Warning!

• 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.

Use with caution in

• Elderly people.
• Decreased liver function.
• Decreased kidney function.
• People with a history of heart failure or a weak heart (especially left ventricular failure).
• Sick sinus syndrome - a problem common in the elderly that affects the heart.
• Narrowing of the main artery coming from the heart (aortic stenosis).

Not to be used in

• Allergy to other related calcium channel blockers (dihydropyridines), eg nifedipine, amlodipine.
• Angina that is increasing in severity, duration or frequency (unstable angina).
• People who are having a heart attack or who have had a heart attack in the last month.
• Failure of the heart to maintain adequate circulation of blood (cardiogenic shock).
• Hereditary blood disorders called porphyrias.
• Rare hereditary problems of galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption (Prescal tablets contain lactose).
• This medicine is not recommended for children.

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 orbreastfeeding. However, other medicines may be safely used in pregnancy orbreastfeeding providing the benefits to the mother outweigh the risks to theunborn baby. Always inform your doctor if you are pregnant or planning apregnancy, before using any medicine.

• The safety of this medicine in pregnancy has not been established. It should therefore not be used during pregnancy unless the benefits to the mother outweigh any possible risks to the unborn child. If this medicine is used at term it may possibly prolong labour by relaxing the muscle of the uterus. Seek further medical advice from your doctor.
• This medicine may pass into breast milk. As there is no information available about the effect of this medicine on newborn babies, the manufacturer recommends that it should not be used by women who are breastfeeding. Seek further 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. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

• Headache.
• Flushing.
• Swollen ankles, wrists, arms or legs.

Common (affect between 1 in 10 and 1 in 100 people)

• Dizziness.
• Faster than normal heartbeat (tachycardia).
• Awareness of your heartbeat (palpitations).
• Shortness of breath (dyspnoea).
• Abdominal discomfort.
• Skin rash.
• Increased need to pass urine (polyuria).
• Fatigue.
• A general feeling of being unwell (malaise).

Uncommon (affect between 1 in 100 and 1 in 1000 people)

• Low blood pressure.
• Increase in weight.

Very rare (affect less than 1 in 10,000 people)

• Visual disturbances, such as blurred vision.
• Sleepiness.
• Mild swelling of the gums (gingival hyperplasia).
• Feeling sick or vomiting.
• Loss of appetite.
• Skin reactions, such as sweating, rash, itching, sensitivity to light.
• Pain in the muscles or joints.
• Impotence (erectile dysfunction).
• Depression.
• Anxiety or nervousness.
• Pins and needles or numb sensations.
• Alteration in results of liver function tests.
• Inflammation of the liver (hepatitis).
• Decrease in the normal numbers of red blood cells, white blood cells and platelets in the blood (anaemia, neutropenia, thrombocytopenia).
• Chest pain.
• Irregular heartbeats.

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 already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

Isradipine may have an additive effect with other medicines that decrease blood pressure, particularly other medicines used to treat high blood pressure (antihypertensives). If the combination of medicines lowers your blood pressure too much this could make you feel dizzy. If this happens to you, you should sit or lie down until the symptoms pass. If you frequently feel dizzy when taking isradipine in combination with other medicines that can lower blood pressure you should let your doctor know, as your doses may need adjusting. Other medicines that can decrease blood pressure include the following:

• ACE inhibitors, eg enalapril
• alpha-blockers such as prazosin
• alprostadil
• angiotensin II receptor antagonists such as losartan
• antipsychotics
• benzodiazepines, eg temazepam, diazepam
• baclofen
• beta-blockers such as propranolol
• other calcium-channel blockers, eg verapamil, nifedipine
• clonidine
• diazoxide
• diuretics, eg furosemide, bendroflumethiazide
• dopamine agonists, eg bromocriptine, apomorphine
• hydralazine
• levodopa
• MAOI antidepressants, eg phenelzine
• methyldopa
• minoxidil
• moxisylyte
• moxonidine
• nicorandil
• nitrates, eg glyceryl trinitrate (GTN)
• tizanidine.

The following medicines may increase the breakdown of isradipine by the liver. As these could make it less effective they should be avoided while taking isradipine:

• carbamazepine
• phenobarbital
• phenytoin
• primidone
• rifampicin
• the herbal remedy St John's wort (Hypericum perforatum).

The following medicines may decrease the breakdown of isradipine by the liver, which could increase the risk of its side effects. If you take any of these with isradipine, you should tell yourdoctor if you feel dizzy or experience any other side effects, as the dose ofyour isradipine may need to be reduced:

• cimetidine
• clarithromycin
• erythromycin
• itraconazole
• ketoconazole
• protease inhibitors for HIV infection, eg ritonavir, nelfinavir, saquinavir
• telithromycin.

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 indometacin (occasional painkilling doses are unlikely to have a significant effect).

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that contain isradipine as the active ingredient.