Tambocor (flecainide) is one of a group of antiarrhythmics called ‘class I agents’, or sodium-channel blockers. Class II agents are the beta-blockers, and class IV agents are calcium antagonists. Class III drugs are usually prescribed for atrial fibrillation (see Case study, p 8).
The class I drugs are designed to stabilise an irregular heartbeat (arrhythmia) by slowing nerve impulses in the heart, and by anaesthetising heart tissue, making it less sensitive to nerve impulses.
Class I agents are being given to patients for whom the drug was never intended. One report concluded that these drugs are more harmful than helpful in patients recovering from a heart attack (Ann Rev Med, 1994; 45: 119-38).
The Cardiac Arrhythmia Suppression Trial (CAST) had reached a similar conclusion five years earlier when it abandoned its research after finding conclusively that flecainide and encainide, another class I agent, increased death due to arrhythmias and the incidence of cardiac arrest by more than three times the rate with placebo (N Engl J Med, 1989; 321: 406-12).
The CAST results should have radically transformed the use of heart-therapy drugs, but though they did usher in newer and safer agents, the use of class I drugs remains as supreme as ever.