ANTIARRHYTHMIC DRUGS
Antiarrhythmic drugs carry a significant risk of proarrhythmia
along with other cardiovascular and noncardiovascular
adverse effects (Table 1). Drugs with a
low therapeutic index, such as digoxin, or drugs
predominantly renally cleared, such as sotalol, should
be started at low doses. Although most cardiac drugs
can be used in the elderly, amiodarone and digoxin must
be used with caution and at low doses, and the planned
duration of therapy reassessed periodically.7 Dosages
of antiarrhythmic drugs are monitored predominantly on
clinical grounds, but from time to time drug levels are
required for optimising care and avoiding toxicity, e.g.
serum digoxin levels are useful in determining toxicity.
Antiarrhythmic drugs have been traditionally classified
as possessing one or more of the four classes of
antiarrhythmic action described by Vaughan Williams.