A nurse is caring for an older adult client. The nurse should recognize that which of the following considerations apply to older adults and pharmacology? (Select all that apply).

A. Category A:
Medications classified as Category A are considered the safest during pregnancy. They have been well-studied in pregnant humans, and no risk to the fetus has been demonstrated. This classification means that adequate and well-controlled studies have shown no evidence of harm to the fetus in the first trimester and no risk in later trimesters.

B. Category C:
Category C medications have shown potential risks to the fetus in animal studies, and there are no well-controlled studies in humans. The benefits of the medication may outweigh the potential risks, but caution is advised. These medications are used when the potential benefits justify the potential risks to the fetus.

C. Category X:
Category X medications are contraindicated in pregnancy due to evidence of fetal abnormalities or risks that outweigh any potential benefits. These medications have demonstrated clear evidence of harm to the fetus in both human and animal studies, and their use is not recommended during pregnancy.

D. Category B:
Category B medications have shown no risk to animal fetuses, but there is a lack of adequate and well-controlled studies in pregnant humans. The absence of evidence of harm in animal studies suggests that these drugs are generally considered safe, though their effects on human fetuses are not well-documented.

A. Absorption:
Chronic liver failure primarily affects the metabolism of drugs rather than their absorption. While liver disease can impact various bodily functions, the absorption of medications is generally more influenced by gastrointestinal factors and not as directly affected by liver function.

B. Excretion:
Excretion of drugs is primarily managed by the kidneys, not the liver. While liver failure can lead to changes in drug metabolism, it does not directly impair the excretion process, which is largely renal. However, compromised liver function can indirectly affect renal excretion due to altered pharmacokinetics.

C. Metabolism:
Liver failure significantly affects drug metabolism. The liver is the primary site for the metabolism of many medications, converting drugs into more water-soluble compounds for excretion. In chronic liver failure, the liver's ability to metabolize drugs is impaired, leading to potential drug accumulation and increased risk of toxicity. This step of pharmacokinetics is most directly impacted by liver dysfunction.

D. Distribution:
While liver function can affect drug distribution to some extent, it is not as directly impacted as metabolism. Distribution can be influenced by factors such as changes in plasma protein levels and blood flow, but the liver's primary role in drug metabolism is more directly affected by chronic liver failure.