A group of investigators is studying the pharmacokinetic properties of the anesthetic drug propofol. A radiolabeled formulation of the drug is prepared and a single bolus is administered to adult guinea pigs. Blood and tissue samples are then collected at predetermined time intervals. Concentrations of the radioactive drug in the samples are assessed by liquid scintillation counting. The graph below demonstrates the drug concentration-time relationship in various tissues. The red line on the graph most likely corresponds to which of the following tissues?

Question

A group of investigators is studying the pharmacokinetic properties of the anesthetic drug propofol.  A radiolabeled formulation of the drug is prepared and a single bolus is administered to adult guinea pigs.  Blood and tissue samples are then collected at predetermined time intervals.  Concentrations of the radioactive drug in the samples are assessed by liquid scintillation counting.  The graph below demonstrates the drug concentration-time relationship in various tissues.  The red line on the graph most likely corresponds to which of the following tissues?

Quizplus · Accepted Answer

11ec160b_3c27_1c24_9249_5b5bcbefb4cf_MD0001_00 Drug distribution is not uniform; the rate at which drugs are delivered to target tissues is dependent on several factors, such as regional blood flow and drug characteristics. The pharmacokinetic profile of highly lipophilic anesthetic drugs, such as propofol, can be predicted using a multi-compartment model of distribution. Following administration of a single intravenous bolus, drug levels are high in the central compartment (ie, plasma). However, the drug is quickly distributed to the well-perfused peripheral compartment (eg, brain, liver, kidneys, lungs) due to the increased lipophilicity of the tissues compared to the blood. Over time, drug redistribution will occur through the central compartment into the poorly-perfused peripheral compartment (eg, skeletal muscle, fat, bone), which has the highest volume of distribution for lipophilic agents. Redistribution occurs rapidly with highly lipophilic drugs and is responsible for the short duration of action seen with commonly used anesthetics such as propofol. (Choices A, B, C, and D) These organs have relatively high blood flow and are considered part of the well-perfused peripheral compartment. They will rapidly take up drugs from the central compartment and are visualized as the dashed line on the above graph. Educational objective: Following intravenous administration, a highly lipophilic drug will be rapidly distributed to organs with high blood flow (eg, brain, liver, kidneys, lungs). The drug is then redistributed to tissues with relatively lower blood flow (eg, skeletal muscle, fat, bone). This accounts for the short duration of action of many commonly used anesthetics, such as propofol.

A Group of Investigators Is Studying the Pharmacokinetic Properties of the Anesthetic