Comprehensive Nursing Pharmacology Q 299

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Drug distribution is affected by which of the following?

  

     A. Biotransformation

     B. Excretion

     C. Protein binding

     D. Lipid binding

    

    

Correct Answer: C. Protein binding

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Distribution depends on protein binding as well as circulation. Some drugs leave the bloodstream very slowly because they bind tightly to proteins circulating in the blood. Others quickly leave the bloodstream and enter other tissues because they are less tightly bound to blood proteins. Some or virtually all molecules of a drug in the blood may be bound to blood proteins.

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Option A: Biotransformation is the act of metabolizing the drug. Biotransformation is the process by which a substance changes from one chemical to another (transformed) by a chemical reaction within the body. Metabolism or metabolic transformations are terms frequently used for the biotransformation process.

Option B: Excretion describes the act of eliminating the drug. Drug excretion is the removal of drugs from the body, either as a metabolite or unchanged drug. There are many different routes of excretion, including urine, bile, sweat, saliva, tears, milk, and stool. By far, the most important excretory organs are the kidney and liver.

Option D: There is no such thing as lipid binding. The protein-bound part is generally inactive. As unbound drugs are distributed to tissues and its level in the bloodstream decreases, blood proteins gradually release the drug bound to them. Thus, the bound drug in the bloodstream may act as a reservoir for the drug.

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