Calcium Channel Blockers

Calcium channel blockers are one of the key drugs administered in cardiovascular conditions. In most cases they are used in case of hypertension and angina.They are classified depending upon their mode of action and their chemical composition. These chemicals when induced in the body block the calcium channels in the cell membrane.

Dihydropyridines

They are selected for vascular sites rather than the myocardial region. These drugs facilitate good vasodilator effects with limited electro physiological effect on the cardiac conduction system pertaining to the AV and SA nodes. Thus the negative inotropic effects do not occur in these drugs.These drugs are more selective to the cerebral arteries than the systemic arteries. Eg: Nifedepine, Amlodipine, nimodipine.

Diphenylalkylamines

These drugs cause peripheral vasodilation with a moderate inotropic effect. Subsequently they increase the coronary vasodilation. Cardiac rate may or may not increase as it causes a slight depression in the SA or AV nodal conduction route. Eg: Verapamil.

Benzothiazepines

These drugs are also associated with peripheral vasodilation causing mild inotropic effect and minimum depression in the SA / AV node conduction. They increase coronary vasodilation. They also exhibit intermediate vaso-selectivity. Eg: Diltiazem.

The elimination route for most of these drugs is through the liver. In most cases the recommended dosage is twice a day for sustained release in the body. The limitation of calcium channel blockers administration for hypertension is often related to their functionality such as vasodilation. However, because of their mechanism of action and efficacy, they do not cause conditions such as reflex tachycardia.

Calcium channel blockers are given to children who have low renin levels. The drug is given with other drugs such as beta-blockers and diuretics to attain desired results of cardiac physiology. In most cases, calcium blocker administration requires investigative tests such as blood vessel abnormalities, liver and kidney function tests.

Side effects and precautions

Calcium channel blockers are known to have some side effects since they are closely associated with vascular physiology and cardiac conduction system. Syncope and presyncope episodes followed by dizziness are commonly-noticed side effects. This happens because of the decrease in blood pressure due to reduced heart rate. Arrhythmia is another potential side effect along with gastro-esophageal reflux and nausea.

Lower extremity swelling or edema is a complication of treatment with calcium channel blockers (especially with Felodipine and Amlodipine), Thioglitazones and Minoxidil. Transient Incontinence is another symptom noticed with Calcium Channel Blocker drugs.

The most common side effects of calcium channel blockers are peripheral edema, Bradycardia, headache and constipation in some cases. The dihydropyridine agents such as Nifedipine, Nicardipine, Isradipine, Felodipine, Nisoldipine and Amlodipine, can produce symptoms of vasodilation - specifically headaches, palpitations, flushing and peripheral edema or swelling in lower extremities.

Some studies indicate that juices such as grapefruit should be avoided during the administration of calcium channel blockers as they hinder with the drug absorption and breakdown in the system. Alcohol consumption must also be avoided as it may cause damage because of hepatic involvement in the respective drug.

Calcium channel blockers are taken as second line cardiac drugs with respect to anti-hypertensive drugs and beta-blockers. However careful examination of the patient drug history is performed before recommending these drugs because some studies also imply that prolonged usage of all three drugs may increase the incidence of diabetes and the risks associated with it. Drug evaluation is essential because recent studies indicate the involvement of clarithromycin along with calcium channel blockers causing kidney damage and prolonged usage of these drugs can also cause breast cancer in women.

Anti hypertensive drugs

Anti hypertension drugs can be classified into 8 broad categories depending upon their mode of action. In this collection of health articles, we strive hard to impart information with no commercial bias and hence you may not find any commercial name of the drugs or brand names as far as possible. Instead we may present the generic names of the drugs.

To control the high blood pressure, your doctor may use one of the following group of drugs:

• Diuretics
  
  
• Beta blockers
  
  
• Angiotensin Converting Enzyme (ACE) inhibitors
  
  
• Calcium channel blockers
  
  
• Angiotensin Receptor Blockers
  
  
• Alpha Blockers
  
  
• Centrally acting drugs
  
  
• Direct vasodilators
  
  

Ischemia

Ischemia is one of the most studied medical conditions. It is associated with various infectious and non-infectious medical conditions. The term ischemia is derived from the Greek word Icheim (restrain) referring to the lack of blood supply to a respective tissue. The occurrence of ischemia in the body triggers many biochemical abnormalities in the body therefore creating insufficiency of metabolites to the tissue.

Studies indicate that almost fifty percent of deaths around the world happen because of ischemia. The most prevalent forms of ischemia are associated with the cardiovascular system and brain. Ischemia progresses itself in to metabolic disorders such as hypoxia. Hypoxia is a fatal condition in which there is oxygen deficiency to the cells causing cellular damage and death. The predisposing factors for hypoxia may include blockage of arteries in a respective circulatory region preventing the blood supply. Ischemia gradually results in tissue necrosis and damage to blood vessels restricting the flow of blood into the tissues.

Biochemical changes such as accumulation of metabolized waste products occur as a result of ischemia in relation to conditions such as embolism, atherosclerosis, thrombosis and compression. This metabolic waste accumulation eventually leads to increase in toxin levels in the body. Cell death is one of the main outcomes of ischemia. The complications of ischemia range from reversible forms to irreversible forms depending on the type of organ damage.

Physiological studies indicate the significance of parenchyma cells in the occurrence of ischemia. Parenchyma cells located in each organ have a specific threshold. In the cardiac muscle, the threshold levels are 20-30 min whereas in the neural cells it is only 3-4 min. Parenchyma cells are more prone to damage than the cells of the stoma and hence the difference in these threshold values indicate the exact etiology of ischemia.

Ischemia occurring in the cardiac region is predominantly because of the hypoxia present in the sub endocardial region. Simultaneously in the central nervous system, it is because of the watershed infarcts. Hence the effect of ischemia is directly proportional to the micro vascular anatomy of the organ systems. Another form of ischemia is silent ischemia. It is an asymptomatic condition often found in people who are old, women and have a history of diabetes. Silent ischemia does not present any visible clinical signs of illness, however through diagnostic examinations such as electrocardiogram and stress testing; the insufficient blood supply to the cardiac muscle can be identified.

Mesenteric Ischemia

Acute mesenteric ischemia is caused due to inadequate blood flow the the mesentery artery and results in tissue hypoxemia. Symptoms such as acute abdominal pain, nausea, diarrhea and vomiting are noticed. Some feel acute pain on eating - 'abdominal angina'. The narrowed mesenteric artery is usually a result of chronic atherosclerosis. Anticoagulation and vasodilation are resorted to. Often surgery is done to treat mesenteric ischemia due to embolus or thrombosis.

Treatment

Ischemia is treated by administering blood thinning drugs such as aspirin. This is done to prevent the clot formation in the blood vessels. Temporary opening of the arterial walls is done by using nitro-glycerine medication. Since ischemia is the precursor for the occurrence of tachycardia, beta blockers are used to relax the heart muscle. Other medications include calcium channel blockers and cholesterol lowering drugs.