Atrial fibrillation (AF) is the most common type of cardiac arrhythmia. Treatments aim to slow the heart rate - using a beta-blocker (propranolol, acebutolol, atenolol, metoprolol, nadolol, oxprenolol, sotalol), a rate-controlling calcium-channel blocker (verapamil) or digoxin - and control the rhythm using an anti-arrhythmic (amiodarone, disopyramide, flecainide) . Patients with AF are at high risk of stroke so are usually on an anticoagulant (usually warfarin, but sometimes aspirin).

Dosage Regimen

* Beta blocker dosages differ according to the agent being used: some need to be given two to three times a day, others have a longer duration of action or are manufactured in modified-release preparations so only need to be given once daily.

* Verapamil is taken three times a day. Modified-release preparations are not licensed for use in AF.

* Digoxin has a long half-life so only requires once daily administration.

* Anti-arrhythmics are usually taken two to three times a day.

* Warfarin is taken once daily. The daily maintenance dose is usually 3-9mg.

Patient's knowledge of the medicine's use

* Explain to AF patients that beta-blockers, verapamil and digoxin slow the heart rate, whereas anti-arrhythmics normalise the cardiac rhythm. Warfarin is used to prevent the development of blood clots as a result of AF.

Is the medicine working?

* Has the patient been taking the correct dosage of their medication?

* Has the patients symptoms/condition deteriorated? If so, refer back to the prescriber.

* Is the patient taking any OTC/herbal remedies, which may interact with their medication?

Side effects

* Beta-blockers can cause sleep disturbances, bradycardia, fatigue, coldness of the extremities and sexual dysfunction. They can also precipitate asthma and interfere with glucose tolerance.

* Calcium-channel blockers: Common side effects include flushing, ankle oedema, headache, bradycardia and hypotension.

* Digoxin: Side effects usually only occur with excessive dosage and can include anorexia, nausea, vomiting, diarrhoea, visual disturbances, fatigue, drowsiness and confusion. Toxicity is usually managed by discontinuing the digoxin. Diuretics can precipitate hypokalaemia which can be dangerous in patients also receiving digoxin. Lower doses of diuretics should be used in the elderly and in patients with impaired renal function. Other side effects of diuretics include mild GI disturbances and postural hypotension.

* Amiodarone can cause taste disturbances, nausea and vomiting, bradycardia and liver or thyroid problems. Visual disturbances can also occur and should be reported immediately. Amiodarone can also cause photosensitivity reactions, so patients should be advised on the need to use sunscreen during treatment.

* Disopyramide can cause tachycardia and hypotension. It has antimuscarinic activity so can cause dry mouth, blurred vision and urinary retention and may precipitate glaucoma.

* Flecainide commonly causes nausea and vomiting, and can cause dyspnoea and visual disturbances.

* Warfarin: Patients should be warned of the signs of over-anticoagulation, such as bruising, subconjunctival haemorrhage and bleeding, and advised to seek medical advice as soon as possible. Other side effects include rash and diarrhoea.

Monitoring

* Beta-blockers: Heart rate, blood pressure, electrolytes, urea and creatinine and clinical status should be assessed after each increment of beta-blocker therapy. Monitoring should also include a clinical assessment of functional capacity, fluid status, cardiac rhythm, cognitive and nutritional status.

* Calcium-channel blockers: Heart rate and blood pressure should be monitored regularly.

* Digoxin: Routine monitoring of serum digoxin concentrations is not recommended, but may prove useful to confirm non-compliance if conducted within eight to 12 hours of the last dose. However, these should be interpreted cautiously as digoxin toxicity can occur even when concentrations are within the therapeutic range.

* Amiodarone: Liver and thyroid function tests should be performed before commencing treatment and at six monthly intervals. Serum potassium and a chest X-ray should also be taken before starting amiodarone.

* Disopyramide: Blood pressure and cardiac rhythm should be carefully monitored.

* Flecainide can cause serious arrhythmias so cardiac function should be monitored.

* Warfarin: International normalised ratio (INR) must be monitored, initially daily or on alternate days, then at longer intervals depending on response. The target INR is usually 2.5.

Lifestyle

* General "healthy heart" measures should be adopted, such as stopping smoking, losing weight, eating a diet low in fat and salt, taking regular exercise, avoiding stress and caffeine and reducing alcohol intake.

* Patients should be advised that they may be eligible for a "one-off" pneumococcal vaccination and a yearly flu vaccination.

* Patients on warfarin should carry a yellow treatment book with them at all times, and be aware of substances that can interfere with the drug's anticoagulant action, such as aspirin, St John's wort, vitamin K, and cranberry and grapefruit juices.

Kevin Alexander, community pharmacist, Hafod Pharmacy, Swansea / Ken Wan, pharmacist, Clacton-on-Sea, Essex / AF

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