Calcium channel blockers, also called calcium antagonists, are mainly prescribed for high blood pressure and other cardiovascular issues. Renin is an enzyme that the kidney cells release in certain situations, and one function of renin is to raise blood pressure, explains Merck Manuals Online Medical Library. Different calcium channel blockers have different effects on renin.
Calcium Channel Blocker Benefits
Calcium channel blockers decrease the rate at which calcium travels into the blood vessels and the heart, an effect that relaxes blood vessels and allows them to widen, notes MayoClinic.com. Some calcium channel blockers also slow the heart rate. Doctors prescribe these medications to treat high blood pressure, pulmonary hypertension, arrhythmia, angina, certain circulatory disorders and migraine headaches. Examples of calcium channel blockers include mibefradil and amlodipine.
Renin Function
The kidneys release renin when the body has decreased sodium levels or low blood volume. The release of renin leads to production of the hormone angiotensin II, which stimulates the release of aldosterone, a hormone involved in regulating the body's salt and water balance, explains the U.S. National Institutes of Health. In addition, angiotensin II is important for regulating blood pressure; it helps raise it, when necessary, by causing the muscles surrounding blood vessels to contract.
Interactions
Animal research published in the June 1998 issue of the British Journal of Pharmacology found that some types of calcium channel blockers lower renin---known as T-type---while other types increase it. Mibefradil is a calcium channel blocker that inhibits calcium ions from traveling across T-type calcium channels. Although mibefradil also inhibits this movement across L-type calcium channels, it has a greater selectivity for T channels and is known as a T-type calcium channel blocker.
L-type calcium channel blockers, such as amlodipine, stimulate renin release. Calcium channel blockers are actually more effective for people who have high blood pressure and low renin, a condition commonly associated with salt sensitivity, explains MedlinePlus. The manufacturer of mibefradil, Roche, voluntarily withdrew the drug from the worldwide market in 1998 due to potentially harmful drug interactions.
Salt-Sensitive Hypertension
About 25 percent of people with primary hypertension, or high blood pressure not caused by another health disorder, have low renin levels, according to UpToDate. This situation is more common in people of African descent and the elderly. In these persons, elevated blood pressure is more likely to be a salt-sensitive condition, and lifestyle changes such as weight loss are not as effective as they are for other patients with high blood pressure.
Significance
Although calcium channel blockers are not usually the first choice for high blood pressure treatment, people who are salt sensitive and have high blood pressure and low renin levels tend to respond well to these medications. Diuretics also are effective. If you have high blood pressure, your doctor may order a blood test to measure renin and aldosterone levels to indicate sensitivity to salt. Salt sensitivity causes low renin with normal aldosterone levels, explains MedlinePlus. The test results help your doctor choose the best medication for you.
