Calcium channel blockers are medicines used to control high blood pressure, or hypertension. There more than 10 different drugs that fall under the category of calcium channel blocker. Apart from hypertension, calcium channel blockers are used to treat abnormal heart rhythms, or arrhythmias; migraine headaches; a type of brain bleed called subarachnoid hemorrhage; and congestive heart failure. According to the Utah Poison Control Center, calcium channel blockers are the most common cardiovascular drugs involved in ingestions, resulting in significant toxicity.
Mechanism of Action
Calcium channel blockers lower blood pressure by dilating the blood vessels in the body. One of the causes of hypertension is that arteries, the blood vessels that carry refreshed blood from the heart, become narrow, forcing the heart to pump harder and increasing the blood pressure. According to Dr. Robert W. Piepho at Emory University, calcium channel blockers stop the influx of calcium into cells. Calcium is an important element in the contraction or narrowing of blood vessels, so by stopping the influx of calcium into those cells, calcium channel blockers cause relaxation and enlargement of the vessels, decreasing the pressure the heart needs to pump blood.
Causes of Toxicity
The causes of calcium channel blocker toxicity include ingestion of long-lasting formulations of the drugs and interaction of these medicines with other pharmaceuticals. The calcium channel blockers are eliminated from the body by the liver, so any condition that affects the liver can prolong the effect of these medications and predispose the person to toxicity. Also, taking medicines like antifungal drugs, which interfere with the liver enzymes in charge of eliminating the calcium channel blockers, can also result in toxicity.
Symptoms
The symptoms of calcium channel blocker toxicity depend on the class of drug taken. The Utah Poison Control Center reports that, in general, symptoms of toxicity include low blood pressure, loss of consciousness, lethargy, dizziness, and other changes in mental status like confusion. The drugs can also diminish the force of the heart's contractions, resulting in the pooling of blood and fluid in the lungs, called pulmonary edema, which can cause shortness of breath, difficulty breathing and hypoxia, or decreased oxygen in the blood and the tissues. Some calcium channel blockers can cause nausea, vomiting and high blood glucose.
Treatment
The treatment of any acute ingestion starts by making sure the person's airway is open and not at risk of collapsing, by making sure the person is breathing adequately, and by checking to see that the heart is pumping blood to the brain and the rest of the body. Liquid charcoal, a thick substance that prevents the absorption of drugs from the gut, can be administered by mouth in cases of acute ingestion, especially if the person took several of the long-lasting or continuous-release formulations. Medicines to improve the heart's pumping ability or increase blood pressure can also be administered if needed.
