Quinidine is a medication used to stabilize heart rhythm in patients with severe arrhythmia. It works by regulating electrical activity in the nerve cells that stimulate the heart muscles. Quinidine is usually prescribed to be taken once or twice daily by mouth at precise intervals. A high-strength injected solution of the drug may also be used in hospitals to combat life-threatening heart problems. The drug is highly effective in a majority of cases, though there are risks of potentially serious side effects and adverse health complications.
Antiarrhythmic agents such as quinidine regulate the heartbeat by controlling the flow of sodium into heart muscle and nearby nerve cells. Sodium channels are present along cell membranes that allow blood-borne sodium to enter. Inside a muscle or nerve cell, sodium elicits an electric impulse that causes contractions. Quinidine is a sodium channel blocker, meaning that it prevents the chemical from entering cells. As a result, the frequency and strength of electrical impulses is significantly decreased.
People who have irregular heartbeats due to congenital defects, inherited diseases, or acquired conditions such as high cholesterol and high blood pressure can benefit from daily doses of quinidine. The drug can help whenever the heart rate is too fast, too slow, or fluctuating. A doctor can determine the proper dosage amount by analyzing imaging scans of the heart, blood tests, and electrical activity screenings. Most adult patients are instructed to take a single 200 or 300 milligram tablet with water every eight to twelve hours. Special dietary restrictions, such as limiting salt intake, may be put into place when the drug is prescribed.
Most patients are able to take regular doses of quinidine without experiencing major side effects. The most common reactions to the drug include stomach cramps, diarrhea, mild headaches, and fatigue. Some people experience lightheadedness, changes in vision and hearing, hand tremors, and chest pains. Since quinidine affects how fast the heart beats, it can potentially cause a sudden drop in blood pressure that may result in heart or lung failure.
The risks of side effects can be limited by following a doctor's instructions and attending regular medical appointments. During the course of treatment, patients need to have their blood pressure, heart rate, and breathing monitored frequently. A doctor may decide to switch to a different medication or adjust dosage amounts if major side effects occur or if a patient's condition fails to improve after several weeks of treatment.