Which statement indicates a correct understanding of topical drug absorption in a pediatric patient?.

Answer is d. Drug elimination will be slowed. In obese patients, the elimination half-life (T1/2) of lipid-soluble drugs is increased due to their accumulation in fat stores. This leads to a slower drug elimination process.

a. Drug distribution will be more rapid: Incorrect because obesity affects drug distribution due to an increased volume of distribution (Vd) for lipid-soluble drugs. This is primarily due to the greater amount of adipose tissue in obese individuals, which serves as a reservoir for lipid-soluble drugs, leading to a larger apparent volume of distribution. However, this does not result in more rapid distribution but rather a prolonged distribution phase as the drug is distributed throughout the body.

b. Drug metabolism will be incomplete: This statement is too vague and does not directly relate to the pharmacokinetics of lipid-soluble drugs in obese patients. Drug metabolism can be affected by various factors including hepatic function, enzyme activity, and genetic polymorphisms, but the incompleteness of metabolism is not a characteristic feature of obesity.

c. Drug absorption will be impaired: Incorrect, as obesity can lead to increased absorption of oral medications due to increased gastric emptying. However, this primarily affects the absorption phase of pharmacokinetics, not elimination. In fact, increased absorption due to altered gastric emptying may result in higher initial plasma concentrations of the drug but does not directly impact its elimination rate.

d. Drug elimination will be slowed: Correct. In obese patients, the elimination of lipid-soluble drugs is slowed down due to their increased accumulation in fat stores. This is primarily attributed to the lipophilic nature of these drugs, which leads to their sequestration in adipose tissue. Consequently, the prolonged elimination half-life results in slower clearance of the drug from the body, leading to potentially prolonged pharmacological effects and increased risk of adverse reactions.

In summary, the correct answer is d because in obese patients, the pharmacokinetics of highly lipid-soluble drugs are characterized by slowed drug elimination, which is primarily due to the increased accumulation of these drugs in adipose tissue. This understanding is crucial for optimizing drug dosing and minimizing the risk of adverse effects in obese patients.

Choice A rationale:

Absorption is not primarily affected by the functioning of hepatic enzymes.

Choice B rationale:

Distribution is not the main concern when dealing with abnormal functioning of hepatic enzymes.

Choice C rationale:

Excretion is mainly a function of the kidneys, not the liver.

Choice D rationale:

Metabolism is the aspect of pharmacokinetics most affected by the functioning of hepatic enzymes. The liver plays a crucial role in the metabolism of drugs.