Anti-Arrhythmic Drugs continued...
But some people with AFib do struggle daily with fatigue, shortness of breath, and dizziness that may accompany the condition. In that case, doctors may recommend one of a number of medications. The one they choose for you will depend on a number of factors -- for example, certain anti-arrhythmic drugs are not suitable for people who also have other underlying heart disease.
The two main categories of drugs that are used specifically to control rhythm are:
- Sodium channel blockers, which decrease the speed of electrical conduction in the heart muscle. These include drugs like disopyramide, flecainide, and propafenone. “They can’t be used in patients with coronary disease or any kind of heart failure,” cautions Wylie.
- Potassium channel blockers, which slow nerve impulses in the heart. They include dofetilide and sotalol. “Because they affect the kidneys, they can’t be given to patients with renal dysfunction,” Wylie explains. Dofetilide also poses a risk of causing life-threatening ventricular arrhythmias, so it must be started in the hospital. That way, the patient can be carefully monitored during the first few days of therapy, when most of these complications happen.
Most of the common anti-arrhythmic drugs have similar success rates: anywhere between 45% and 55%, says Wylie.
Then there’s amiodarone (Cordarone, Pacerone), which is a bit of a hybrid. It’s both a sodium channel blocker and a potassium channel blocker. It’s by far the most effective anti-arrhythmic drug available -- possibly as much as 75%, Wylie says. But because it lingers in many parts of the body for a long time, it has many possible side effects, including lung, liver, and thyroid damage.
“Because of this, we usually will not prescribe it in people who are younger and likely to be treated for a long period of time,” says Whang. If you’re on amiodarone, you’ll have to have regular liver, lung, and thyroid function tests.
There’s also a somewhat controversial new drug called dronedarone (Multaq). “It was designed to be like amiodarone without the side effects, but it turned out to be amiodarone with some of the side effects and none of the efficacy,” says Wylie. “The trials showed that it didn’t keep people in sinus rhythm very well.”
The drug’s manufacturers say that it didkeep people with atrial fibrillation out of the hospital more effectively, however. “It may not prevent AFib, but it might prevent some of the symptoms of AFib, perhaps by blunting fast heart rates,” Wylie concedes. “I rarely use it, but some people love it because it does make some people feel better, and after all, we’re treating for symptoms.”
But in January 2011, the FDA reported two cases of acute liver failure, requiring a transplant, tied to dronedarone. “That didn’t show up in the trials, but if we start seeing more of this, then you’ve got a drug that doesn’t work all that well and is toxic,” Wylie says.