Final answer:
When a highly bound drug is displaced by another highly bound drug, it can result in a decrease in the drug effect of the first drug administered. The displacement can increase the amount of unbound drug in the plasma, which is the active form of the drug that can exert its pharmacological effects.
Step-by-step explanation:
When a drug that is highly bound to the plasma is displaced by another administered drug that is also highly bound, it can lead to a decrease in the drug effect of the first drug administered. This is because the displacement of the first drug by the second drug can increase the amount of unbound drug in the plasma, which is the active form of the drug that can exert its pharmacological effects. The bound form of the drug is not able to cross membrane barriers and reach its intended target, so an increase in the unbound drug may result in a decrease in the overall drug concentration at the target site.
For example, if Drug A is highly bound to plasma proteins and is displaced by Drug B, which is also highly bound, the displacement of Drug A by Drug B can increase the amount of unbound Drug A in the plasma. This can lead to a decrease in the concentration of Drug A at its target site, reducing its pharmacological effect. It is important to consider drug-drug interactions and plasma protein binding when administering multiple drugs that are highly bound to plasma proteins, as these interactions can affect the overall effectiveness of the drugs.