What is it used for?

• High blood pressure (hypertension).
• As a regular long-term treatment to prevent angina attacks.

How does it work?

Verapamil works by slowing down the movement of calcium through muscle cells that are found in the heart and the walls of blood vessels. It does this by blocking 'calcium channels' on these muscle cells. Calcium is needed by the muscle cells in order for them to contract. By depriving them of calcium, verapamil causes the muscle cells to relax. This action of verapamil has two main effects; it slows down the rate at which the heart beats and it allows the blood vessels in the body to widen.

When the heart beats more slowly, the pressure at which the blood is pumped out of the heart is reduced. When the blood vessels in the body relax and widen, this decreases the resistance that the heart has to push against in order to pump the blood around the body. Both these actions reduce the pressure within the blood vessels. This means verapamil can be used to lower high blood pressure.

Slowing the heart rate also reduces the energy used by the heart to pump blood around the body. This in turn reduces the heart's need for oxygen. At the same time, widening the blood vessels improves the blood and therefore oxygen supply to the heart. Both these features mean that verapamil can be used in the management of angina.

The chest pain of angina is caused by insufficient oxygen supply to the heart. As verapamil improves this oxygen supply, and also reduces the effort the heart has to make to pump blood, it can be used to prevent angina attacks.

Verap tablets are a long-acting or 'modified-release' form of verapamil. This means that they are designed to release the verapamil slowly and continuously over several hours to produce a steady blood level of the medicine throughout the day.

How do I take it?

• Verap tablets can be taken with or without food.
• The tablets should be swallowed whole with a drink of water. They should not be broken, crushed or chewed, as this can damage the modified-release action.
• The dose prescribed and how often the medicine needs to be taken depends 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.
• You should not drink grapefruit juice while you are taking this medicine, as it can increase the level of verapamil in your blood and thus increase the chance of getting side effects.

Key Points

This medicine may cause fatigue and dizziness. You should take care when performing potentially hazardous activities, such as driving or operating machinery, until you know how this medicine affects you and are sure you can perform such activities safely.
If you drink alcohol while taking this medicine you should be aware that verapamil may slow the breakdown of alcohol by the body. This means it could increase the level of alcohol in your blood and its effect.
This medicine should not be used to treat an attack of angina, as it won't work quickly enough.
If you go into hospital or to the dentist to have an operation you should tell the person treating you that you are taking this medicine. This is because your blood pressure may fall too low if you are given certain types of anaesthetics while taking this medicine.

Use with caution in

• Decreased liver function.
• Decreased kidney function.
• People with a slow heart rate.
• People with slowed conduction of electrical messages between the chambers of the heart (1st degree heart block).
• Heart failure.
• Conditions in which there are problems with transmission of messages between the nerves and muscles.

Not to be used in

• People who have had a heart attack (myocardial infarction)) complicated by a slowed heart rate, heart failure or very low blood pressure.
• Failure of the heart to maintain adequate circulation of blood (cardiogenic shock).
• People with a serious defect in the heart's electrical message pathways, resulting in decreased function of the heart (2nd or 3rd degree heart block), unless an artificial pacemaker is fitted.
• People with decreased function of the heart caused by failure of the electrical impulse that causes the heart to beat to leave the pacemaker of the heart (sino-atrial heart block).
• A problem called sick sinus syndrome, which is common in elderly people and is related to poor control of the working of the heart (although this medicine may be used in people with this condition who have an artificial pacemaker fitted).
• Uncontrolled heart failure.
• People with a very slow heart rate (less than 50 beats per minute).
• People with low blood pressure (hypotension) of less than 90mmHg systolic.
• People with an irregular heartbeat called atrial flutter or fibrillation that is associated with heart conditions such as Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome.
• Hereditary blood disorders called porphyrias.
• Verap tablets are not recommended for children under 12 years old.

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

• This medicine should be used with caution during pregnancy and only if the potential benefits outweigh any possible risks to the developing baby. It should be avoided during the first trimester unless considered essential by your doctor. Seek further medical advice from your doctor.
• The medicine passes into breast milk in small amounts. At normal doses it is unlikely to be harmful to a nursing infant. However, the manufacturer states it should be only be used during breastfeeding if considered essential by your doctor. Seek further medical advice from your doctor.

Side effects

• Constipation.
• Flushing.
• Headache.
• Nausea and vomiting.
• Dizziness.
• Fatigue.
• Ankle swelling.
• Pins and needles sensations.
• Muscle weakness.
• Aching muscles or joints.
• Slowed heart rate.
• Low blood pressure (hypotension).
• Heart block or heart failure.
• Impaired liver function.
• Reversible enlargement of the gums (gingival hyperplasia) with long-term use.
• Reversible enlargement of the breasts has been seen in elderly men under long-term treatment.
• Impotence (erectile dysfunction).
• Allergic skin reactions.

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?

If verapamil 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 verapamil with one of these medicines. If you feel dizzy or faint 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
• aldesleukin
• 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 diltiazem, 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
• tizanidine.

There may be an increased risk of a slowed heart rate, low blood pressure and heart failure if beta-blockers (for example atenolol, propranolol, timolol) are used in combination with verapamil. Beta-blocker eye drops (used to treat glaucoma) have also been reported to have this effect. It is recommended that beta-blockers are not given by injection to people taking verapamil.

There may be an increased risk of a slowed heart rate, low blood pressure and heart failure if medicines for irregular heartbeats (antiarrhythmics, for example amiodarone, disopyramide, flecainide) are used in combination with verapamil.

Verapamil 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 reduce your dose of these medicines if you take them in combination with verapamil:

• aliskiren (should not be used in combination with verapamil)
• atorvastatin
• buspirone
• carbamazepine
• ciclosporin
• cilostazol
• colchicine (colchicine should not be used in combination with verapamil in people who have liver or kidney problems)
• dabigatran
• darifenacin
• digoxin
• doxorubicin
• dutasteride
• eplerenone
• everolimus
• imipramine
• ivabradine (not recommended in combination with verapamil)
• midazolam
• quinidine
• ranolazine
• simvastatin
• sirolimus
• tacrolimus
• theophylline.

The following medicines may increase the blood level of verapamil. If you take any of these with verapamil, you should tell your doctor if you feel dizzy or experience any other side effects, as the dose of your verapamil may need to be reduced:

• cimetidine
• itraconazole
• macrolide antibiotics such as erythromycin, clarithromycin or telithromycin
• protease inhibitors for HIV infection, such as ritonavir.

The following medicines may increase the removal of verapamil from the body and could therefore make it less effective. If you take any of these in combination with verapamil your doctor may need to increase your verapamil dose:

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

If verapamil is taken in combination with lithium the level of lithium in the blood may decrease, which could make it less effective. However, there may also be increased sensitivity to lithium, which could increase the risk of its side effects. Combined use should be well monitored by your doctor. If you take these medicines together it is important to tell your doctor if you experience any new or increased signs of lithium side effects.

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).

References:

https://en.wikipedia.org/wiki/Verapamil

https://www.netdoctor.co.uk/medicines/heart-blood/a7728/verapress-mr-verapamil/

https://www.drugs.com/verapamil.html

https://www.medicines.org.uk/emc/product/5863/smpc

https://medlineplus.gov/druginfo/meds/a684030.html