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Absorption
Antiarrhythmic drugs can be administered orally, intravenously, or through other routes.
Oral medications are typically absorbed through the gastrointestinal tract, while intravenous drugs bypass this step and enter the bloodstream directly.
The absorption of an antiarrhythmic drug can be reduced or the absorption time can be prolonged by the presence of certain foods (eg, milk) or drugs (eg, antacids or cholestyramine) that bind the drug in the gastric lumen.
Distribution
After absorption, a drug enters the plasma and is distributed to a highly perfused "central" compartment consisting of organs such as the heart, kidney, liver, and brain.
From there, it is metabolized and eliminated or redistributed into a more slowly equilibrating, "deep" compartment composed of adipose tissue, muscle, skin, and other tissues.
Many factors determine the volume of distribution of a drug, a theoretical concept that describes the relationship between the drug dose and plasma level expressed as a function of body weight. These include the ability of the drug to enter various tissues, the lipophilicity, and the degree to which the drug is protein bound.
Metabolism
The biotransformation (or metabolism) of most antiarrhythmic drugs occurs in the liver and is mediated by cytochrome P-450 isoenzymes, of which P4502D6 and P4503A4 are 2 of the most important.
Elimination
Metabolites and unchanged drug are eliminated from the body mainly through the kidneys via urine.
Some drugs may also undergo biliary excretion into the feces.
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