Question 1

The distribution of a drug is determined by:

Accepted Answer

All of the factors listed (blood flow to the organ, presence of certain barriers, plasma protein-binding capacity, and solubility of the drug) can affect the distribution of a drug in the body. Blood flow determines how quickly a drug reaches its target organ, barriers such as the blood-brain barrier can prevent certain drugs from entering the brain, protein binding can affect the amount of free drug available for distribution, and solubility can affect how well a drug can dissolve and be distributed in the body. Therefore, all of these factors play a role in determining drug distribution.

Question 2

Which of the following choices is the process by which a substance is transported against a concentration gradient?

Accepted Answer

Active transport is the only process among the choices that can transport a substance against a concentration gradient. This process requires energy in the form of ATP to move molecules or ions from an area of low concentration to an area of high concentration.

Question 3

When the acidity of the tissue increases, as in instances of infection, the effect of a local anesthetic decreases; therefore, the local anesthetic is a weak acid.

Accepted Answer

The first part of the statement is true,the second part is false.Infections lead to an accumulation of acidic waste products,which lowers the pH of the local area.Local anesthetics must penetrate the nerve cell membrane to cause their action.They become more ionized as the pH drops.This property is a characteristic of weak bases,not weak acids.Local anesthetics are weak bases.Weak bases are better absorbed when the pH is greater than the pKa.A weak base is associated and ionized when the pH is less than the pKa.

Question 4

A drug is defined as a biologically active substance that can modify:

Accepted Answer

Drugs are biologically active substances that can modify cellular function by interacting with specific targets, such as enzymes, receptors, and ion channels. While drugs may indirectly affect the environment, pH, and immune response, these are not the primary targets of drug action.

Question 5

One dose of a drug is administered that has a half-life of 8 hours. Assuming first-order kinetics, how much time is needed for this drug to be over 96% eliminated from the body?

Accepted Answer

Assuming first-order kinetics,40 hours would be required for this drug to be over 96% eliminated from the body.Five half-lives are needed to reduce the levels of a drug to 3.125% of the original levels,or eliminate over 96%.For a drug with an 8-hour half-life,this amounts to five half-lives× 8 hours per half-life,or 40 hours.

Question 6

The movement of a drug from one site in the body to other sites is called:

Accepted Answer

The correct term for the movement of a drug from one site in the body to other sites is distribution.

Question 7

The half-life of a drug is most related to its:

Accepted Answer

The half-life of a drug is the time it takes for half of the drug to be eliminated from the body. This is most related to its duration of action, as drugs with longer half-lives will stay active in the body for a longer period of time. Onset and time to peak concentration are more related to the speed of the drug's effects, while safety is a broader concept that can be influenced by multiple factors.

Question 8

Which of the following is true regarding basic principles of drug distribution in the bloodstream?

Accepted Answer

All drugs in the blood are either bound to plasma proteins or free.Only the drug that is free can exert the pharmacologic effect.Only the free drug can pass across cell membranes.The bound drug is a reservoir for the drug.

Question 9

If one dose of a drug is administered and the drug's half-life in the body is 3 hours, what percentage of the drug would be left after four half-lives?

Accepted Answer

The half-life is the time required for a drug level to fall to one half of its concentration.The drug concentration would go to 50% ® 25% ® 12.5% ® 6.25% in four half-lives.The information given is more than sufficient to answer the question.One needs merely to count the number of half-lives and divide the percentage drug in half for every half-life passed since the drug was administered.

Question 10

A noncompetitive antagonist:

Accepted Answer

A noncompetitive antagonist reduces the maximal response of the agonist, but does not bind to the same receptor site as the agonist. Instead it binds to a different allosteric site, causing a conformational change that reduces the efficacy of the agonist. It typically does not cause a shift in the dose-response curve.

Question 11

Drugs that are weak electrolytes will cross body membranes best when they are (1)nonionized, (2)ionized, (3)polar, (4)nonpolar, (5)lipid soluble, (6)water soluble.

Accepted Answer

Drugs that are weak electrolytes will cross body membranes best when they are nonionized,nonpolar,and lipid soluble.These drugs dissociate in solution and equilibrate into a nonionized form and an ionized form.The nonionized,or uncharged,portion acts as a nonpolar,lipid-soluble compound that readily crosses body membranes.The ionized portion of drugs that are weak electrolytes will traverse membranes with greater difficulty because they are less lipid soluble.

Question 12

Which of the following statements is true concerning the mechanism of action of drugs?

Accepted Answer

Drugs either produce the same action as an endogenous agent or block the action of an endogenous agent.Drugs do not impart a new function to the organism;they merely either produce the same action as an endogenous agent or block the action of an endogenous agent.

Question 13

In comparing two drugs, the dose-response curve for the drug that is more efficacious would:

Accepted Answer

The efficacy of a drug is indicated by the maximum effect it can produce, which is represented by the height of the dose-response curve. A more efficacious drug will have a greater curve height.

Question 14

Which of the following statements is (are)true concerning passage across body membranes?

Accepted Answer

The lipid molecules in membranes form a bilayer with hydrophobic tails inside, making the membrane selectively permeable, especially to ions and polar molecules.

Question 15

Which of the following is not a subject of pharmacokinetics?

Accepted Answer

Pharmacokinetics is concerned with the actions of drugs on the body, including the absorption, distribution, metabolism, and elimination of drugs. Physiologic action of drugs is a subject of pharmacodynamics.

Question 16

Which of the following statements is true regarding the therapeutic index (TI)of a drug?

Accepted Answer

The therapeutic index (TI) is defined as the ratio of the median lethal dose (LD50) to the median effective dose (ED50) of a drug. Therefore, option D is the correct statement. Option A is incorrect, as a drug with a larger TI is considered safer since the dose required to produce toxic effects is much higher than the effective dose. Option B is incorrect since the formula for TI is LD50/ED50, not ED50/LD50. Option C is also incorrect since the effective clinical dose is the dose that produces the desired therapeutic effect in 50% of the population, not 50% of the effective dose.

Question 17

When a drug has affinity for a receptor and produces no effect, it is called a(n):

Accepted Answer

A competitive antagonist has affinity for a receptor,combines with the receptor,competes with the agonist for the receptor,and produces no effect.An agonist has affinity for a receptor,combines with the receptor,and produces an effect.Competitive agonist is nonsensical terminology.A physiologic antagonist has affinity for a site different from that of the agonist in question.

Question 18

Increasing the pH of a solution will cause:

Accepted Answer

Weak bases become ionized at low pH and un-ionized at higher pH.If the pH of the site rises,the hydrogen ion concentration will fall.For weak bases,this results in the un-ionized form (B),which can more easily penetrate tissues.Conversely,if the pH of the site falls,the hydrogen ion concentration will rise.This results in an increase in the ionized form (BH⁺),which cannot easily penetrate tissues.

Question 19

Administering a drug of greater potency is better because drugs of greater potency do not require as high a dose.

Accepted Answer

The first part of the statement is false,the second part is true.The absolute potency of a drug is immaterial as long as the appropriate dose is administered.If equally efficacious,both drugs will produce the same effect.Both meperidine and morphine,for example,have the ability to treat severe pain,but approximately 100 mg of meperidine would be required to produce the same action as 10 mg of morphine.The dose of meperidine needed to produce pain relief is larger than that for morphine.Less potent drugs require higher doses to produce therapeutic effects whereas more potent drugs can reach toxic levels at lower doses.

Question 20

When different drugs compete for the same receptor sites, the drug with the stronger affinity for the receptor will bind to:

Accepted Answer

The drug with the stronger affinity for the receptor will bind to more receptors than the drug with the weaker affinity because it has a higher attraction to the receptor. This means that it is more likely to bind to the receptor and occupy it, leaving fewer receptors available for the weaker drug to bind to.

Quiz 2: Drug Action and Handling