Examples of a Blocker Drug

All drugs somehow interfere with the natural progression or processes of the disease they treat. In this sense, almost any drug can be called a "blocker" in some way. However, medical professionals use the term "blocker" more precisely for particular kinds of drugs. Most blockers--also called antagonists by medical professionals--interfere with or block a biochemical receptor or pathway in the body. Others block the transmission of nerve impulses and some block the absorption of certain nutrients.

Adrenal Hormone Receptor Blockers

• Nonsteroidal adrenal hormones such as norepinephrine cause blood vessel constriction at the alpha receptors in the blood vessels and increased heart rate and contraction force at beta receptors in the heart. Blocking the alpha and beta receptors has value in treating numerous cardiovascular and other diseases.

  Alpha blockers cause the blood vessels to open up (vasodilation). The many alpha blockers include doxazosin, prazosin and alfuzosin. The "-zosin" ending indicates an alpha blocker. Beta blockers reduce heart rate and contraction force. They include several drugs with an "-olol" ending, such as metoprolol, atenolol and bisoprolol. Carvedilol and labetalol block both alpha and beta receptors.

Calcium Channel Blockers

• The contraction of muscles in the heart and blood vessel involves a transfer of calcium ions across the cells' membrane through the calcium channel. Calcium channel blockers relax these muscles and cause vasodilation. They have many uses in treating cardiovascular diseases. Calcium channel blockers include many drugs with an "-dipine" ending, such as amlodipine, nifedipine and felodipine, but also diltiazem and verapamil.

Angiotensin II Receptor Blockers

• Angiotensin II results from an enzymatic conversion of angiotensin I. Angiotensin II causes vasoconstriction and regulates sodium and water retention. Blocking the angiotensin II receptors will cause vasodilation, which has value in many cardiovascular diseases. Angiotensin II receptor blockers, often called ARBs, include "-sartan" drugs such as losartan, eprosartan and telmisartan.

Aldosterone Blockers

• Aldosterone, a steroid adrenal hormone, increases water and sodium retention in the kidneys and thereby elevates blood pressure. An article by CT Stier in the fall 2003 edition of Cardiovascular Drug Review lists several additional cardiovascular conditions that aldosterone might influence. Blocking the aldosterone receptors results in water and sodium excretion, lower blood pressure and, ideally, prevention of other negative effects of aldosterone. Aldosterone blockers include spironolactone and eplerenone. The "-one" ending also occurs with other steroidal compounds such as prednisone and cortisone.

Histamine-2 Blockers

• As Pharmacology2000 notes, histamine, which is commonly associated with allergy symptoms and the antihistamines that treat them, also regulates stomach acid secretion. Blocking the histamine-2 receptors in the stomach reduces acid secretion and has value in treating acid reflux disease (heartburn) and ulcers of the stomach and duodenum. Ranitidine, famotidine and nizatidine are histamine-2 blockers.

Other Blockers

• Tumor necrosis factor (TNF), a cellular protein, causes inflammation in rheumatoid arthritis. TNF blockers interfere with the action of TNF to reduce inflammation. They include etanercept, infliximab and adalimumab.

  Neuromuscular blockers prevent muscular nerve impulses from reaching the brain and cause temporary paralysis. Used in surgery locally to prevent limb movement or systemically to facilitate general anesthesia, they include atracurium, cisatracurium and rocuronium.

  The carbohydrate blockers acarbose and miglitol reduce the absorption of carbohydrates from food in the intestines and have use in treating diabetes. The fat blocker orlistat reduces the absorption of fat in the intestines to aid in weight loss.