Risk of Side-Effects with Amiodarone

Amiodarone is one of the most effective heart rhythm drugs. However, unfortunately, long-term treatment with amiodarone, especially when given at a high dosage, can have side-effects.

In one study (CAMIAT) amiodarone was given to patients after a heart attack, the average dose was 200mg daily at 12 months, but a higher dose was used in the initial period.

After an average of about two years, side-effects attributable to amiodarone were:

• about 10% risk of slowing of the thyroid gland
• about 1-2% risk of developing an overactive thyroid gland
• about 1% risk of significant abnormality of routine blood tests of the the liver
• about 2% risk of developing some lung problems.

On rare occasions very serious lung problems can develop. The lung problems slowly improve over several weeks after cessation of the drug. An underactive thyroid gland can be treated easily but an overactive thyroid gland caused by amiodarone treatment may be more difficult to treat. Amiodarone remains in the body for many months, thus side-effects do not improve immediately upon cessation of the drug.

Amiodarone can also cause increased skin sensitivity to sunlight and patients are advised to use strong sunblock, wear hats and long-sleeved clothing when the UV light is intense. On occasions, especially with high dosages, a bluish discoloration of the skin can occur. Amiodarone is also known to sometimes cause other problems, including neurological problems and deposits on the cornea of the eye which rarely cause visual problems. As with all drugs, the list of potential side-effects is much longer.

Paradoxically, some heart rhythm drugs can cause serious heart rhythm disturbances. It is generally agreed that the risk of one of these serious rhythm disturbances (torsades de pointes) is low with amiodarone. There is a small chance that amiodarone may slow the heart down and on very rare occasions a permanent pacemaker is required because of this problem.

It is important to emphasise that the risk of side effects with lower dosages of amiodarone may be less than that outlined above. Medsafe is the Ministry of Health's website with additional consumer information on amiodarone and other drugs. Click here for the Medsafe information page on the "cordarone" brand of amiodarone.

Thus, as with all drugs, the potential benefits from use of amiodarone should be balanced with the potential side-effects. One expects that the risk of side-effects is less now that many patients with atrial fibrillation are prescribed lower dosages of amiodarone. Regular blood tests to check on the thyroid and liver are necessary. A chest XR should be done before treatment, and during treatment (possibly each year).

Dr Hitesh Patel, Cardiologist
Suite 3, level 2
Ascot Integrated Hospital
90 Greenlane Rd East
REMUERA.
Phone 5209399

18th December, 2004