Antilipemic drugs

Antilipemic drugs

Antilipemic drugs are used to lower abnormally high blood levels of lipids, such as cholesterol, triglycerides, and phospholipids. The risk of developing CAD increases when serum lipid levels are elevated. Drugs are used in combination with lifestyle changes (such as proper diet, weight loss, and exercise) and treatment of an underlying disorder causing the lipid abnormality to help lower lipid levels.

The classes of antilipemic drugs include:

• bile-sequestering drugs
• fibric acid derivatives
• 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors
• nicotinic acid
• cholesterol absorption inhibitors.

Bile-sequestering drugs

The bile-sequestering drugs are cholestyramine, colestipol, and colesevelam. These drugs are resins that remove excess bile acids from the fat deposits under the skin.

Pharmacokinetics

Bile-sequestering drugs aren’t absorbed from the GI tract. Instead, they remain in the intestine, where they combine with bile acids for about 5 hours. Eventually, they’re excreted in stool.

Pharmacodynamics

The bile-sequestering drugs lower blood levels of low-density lipoproteins (LDLs). These drugs combine with bile acids in the intestines to form an insoluble compound that’s then excreted in stool. The decreasing level of bile acid in the gallbladder triggers the liver to synthesize more bile acids from their precursor, cholesterol. Getting out of storage

As cholesterol leaves the bloodstream and other storage areas to replace the lost bile acids, blood cholesterol levels decrease. Because the small intestine needs bile acids to emulsify lipids and form chylomicrons, absorption of all lipids and lipid-soluble drugs decreases until the bile acids are replaced.

Pharmacotherapeutics

Bile-sequestering drugs are the drugs of choice for treating type IIa hyperlipoproteinemia (familial hypercholesterolemia) when the patient can’t lower his LDL levels through diet alone. Patients whose blood cholesterol levels place them at a severe risk of CAD will most likely require one of these drugs in addition to dietary changes.

Drug interactions

Bile-sequestering drugs produce the following drug interactions:

• They may bind with acidic drugs in the GI tract, decreasing their absorption and effectiveness. Acidic drugs likely to be affected include barbiturates, phenytoin, penicillins, cephalosporins, thyroid hormones, thyroid derivatives, and digoxin.
• Bile-sequestering drugs may decrease absorption of propranolol, tetracycline, furosemide, penicillin G, hydrochlorothiazide and gemfibrozil.
• Bile-sequestering drugs may reduce absorption of lipid-soluble vitamins, such as vitamins A, D, E, and K. Poor absorption of vitamin K can affect prothrombin times significantly, increasing the risk of bleeding.

Warning!

Adverse reactions to bile-sequestering drugs

Short-term adverse reactions to these drugs are relatively mild. More severe reactions can result from long-term use. Adverse GI effects with long-term therapy include severe fecal impaction, vomiting, diarrhea, and hemorrhoid irritation.

Rarely, peptic ulcers and bleeding, gallstones, and inflammation of the gallbladder may occur.