A patient receiving Morphine for postoperative pain relief displays slow, shallow breathing with a rate of 8 breaths/minute. The nurse recognizes this as a side effect called:

Choice A reason: This is correct. The liver is the main organ responsible for drug metabolism. The enzymes that the body uses to metabolize drugs are present throughout the body but are most abundant in the liver. The liver can transform drugs into more polar and water-soluble compounds, which can then be excreted by the kidneys or the biliary system.

Choice B reason: This is incorrect. The lungs are not primarily responsible for drug metabolism, although they can play a minor role in some cases. The lungs can metabolize some drugs that are inhaled, such as anesthetics, or drugs that circulate through the pulmonary blood vessels, such as propranolol. However, the lungs have a lower capacity and a lower variety of enzymes than the liver.

Choice C reason: This is incorrect. The heart is not responsible for drug metabolism, although it can be affected by it. The heart is the organ that pumps blood throughout the body, delivering oxygen and nutrients to the tissues and organs. The heart can be influenced by the pharmacokinetics and pharmacodynamics of drugs, which are the processes of drug absorption, distribution, metabolism, and excretion, and the effects of drugs on the body, respectively.

Choice D reason: This is incorrect. The kidney is not primarily responsible for drug metabolism, although it is important for drug excretion. The kidney is the organ that filters the blood and removes waste products and excess fluid as urine. The kidney can excrete drugs that are water-soluble or that are not reabsorbed by the tubules. The kidney can also metabolize some drugs, such as aspirin, but to a lesser extent than the liver.

Choice A reason: Distribution is not the correct term to describe the movement of a drug from its site of administration to the bloodstream. Distribution is the process by which a drug moves from the bloodstream to the tissues and organs of the body. Distribution depends on factors such as blood flow, tissue permeability, plasma protein binding, and tissue binding. Distribution occurs after the drug has been absorbed into the bloodstream, and it determines how much drug reaches the site of action.

Choice B reason: Metabolism is not the correct term to describe the movement of a drug from its site of administration to the bloodstream. Metabolism is the process by which a drug is chemically transformed in the body, usually by enzymes in the liver or other tissues. Metabolism can affect the activity, duration, and elimination of a drug. Metabolism occurs after the drug has been absorbed into the bloodstream, and it can occur before or after the drug reaches the site of action.

Choice C reason: Excretion is not the correct term to describe the movement of a drug from its site of administration to the bloodstream. Excretion is the process by which a drug or its metabolites are eliminated from the body. Excretion can occur through various routes, such as urine, feces, sweat, or breath. Excretion occurs after the drug has been absorbed into the bloodstream, and it can occur before or after the drug reaches the site of action.

Choice D reason: Absorption is the correct term to describe the movement of a drug from its site of administration to the bloodstream. Absorption is the process by which a drug enters the bloodstream from the site of administration. Absorption depends on factors such as the route of administration, the dose, the formulation, and the bioavailability of the drug. Absorption is the first step of pharmacokinetics, and it determines how much and how fast a drug reaches the bloodstream and the site of action.