Focus on Pharmacology: Essentials for Health Professionals, 3e (Moini) Chapter 3 Pharmacokinetics

1) Simple diffusion involves:

A) drugs crossing membranes against their gradient from areas of low concentration to high concentration

B) movement of molecules from areas of higher concentration to areas of lower concentration

C) a certain carrier protein

D) unevenly distributed electrical charges

Answer: B

Explanation: B) Simple diffusion involves movement of molecules from areas of higher concentration to areas of lower concentration. Over time, drug molecules are inactivated (metabolized) by tissues, and additional doses may be administered to create a continual concentration gradient, from blood to tissue.

2) Which of the following is false regarding plasma membranes?

A) They contain two layers of phospholipids.

B) They contain cholesterol, carbohydrates, and proteins.

C) Their phospholipids have a round head and one tail.

D) Cholesterol and phospholipids are essential.

Answer: C

Explanation: C) Regarding plasma membranes, their phospholipids do NOT have a round head and one tail. While their heads are round and contain the phosphate, they have two tails, which are long-chain hydrocarbons. Other substances embedded in the membrane include cholesterol, carbohydrates, and proteins.

3) An example of a polar molecule is the:

A) water molecule

B) hydrogen molecule

C) sugar molecule

D) alcohol molecule

Answer: A

Explanation: A) A water molecule is an example of a polar molecule, which has unevenly distributed electrical charges. In the water molecule, the negative electrons remain closer, most of the time, near the oxygen atom in comparison to the two hydrogen atoms. Therefore, the area near the oxygen atom is usually negatively charged, whereas the area near the hydrogen atoms is usually positively charged.

4) The primary site of gastrointestinal (GI) absorption of a drug is the:

A) esophagus

B) stomach

C) small intestine

D) large intestine

Answer: C

Explanation: C) The small intestine is the primary site of GI absorption of a drug, because of its very large surface area, across which drugs may diffuse. Acids are normally absorbed more extensively in the intestines that in the stomach even though the intestines have a higher pH. The higher the pH, the more alkaline; the lower the pH, the more acidic.

5) The speed of systemic availability depends on pharmaceutical factors and:

A) bloodstream absorption

B) gastrointestinal absorption

C) rate of excretion

D) cellular absorption

Answer: B

Explanation: B) The speed of systemic availability (or bioavailability) depends on pharmaceutical factors and gastrointestinal absorption. Pharmaceutical factors include the rate at which a tablet or capsule dissolves, or the use of binding products in formulating the medication. Factors that affect drug absorption include food in the stomach, other drugs taken concurrently, intestinal motility, or certain disease states.

6) Which of the following is false regarding the GI tract and drug absorption?

A) pH partitioning influences absorption.

B) The presence of food in the stomach or intestine influences absorption.

C) Protein solubility influences absorption.

D) Blood flow influences absorption.

Answer: C

Explanation: C) Regarding the GI tract and drug absorption, protein solubility does NOT influence absorption. However, absorption is influenced by pH partitioning, the presence of food in the stomach or intestine, and blood flow. The term pH partitioning refers to a drug's molecules being more likely to be ionized in the plasma, because of differences between plasma pH and the pH at the site of administration.

7) Many drugs are bound to circulating proteins; the most common of which is usually:

A) interferon

B) enzymes

C) glycoproteins

D) albumin

Answer: D

Explanation: D) The most common circulating protein to which drugs are bound is usually albumin. Many drugs are also bound to lipoproteins or glycoproteins. Only the fraction of drugs not bound to protein can bind to cellular receptors, pass across tissue membranes, and gain access to cellular enzymes, thus being distributed to body tissue.

8) During pregnancy, the placenta may transfer drugs that are:

A) ionized

B) lipid-soluble

C) water-soluble

D) metabolized

Answer: B

Explanation: B) During pregnancy, the placenta may transfer drugs that are lipid-soluble from the mother to the fetus. The substances most likely to pass through the placenta are those that are lipid-soluble and nonionized. These agents are linked to birth defects, drug dependency, and respiratory depression.

9) Most drug metabolism occurs in the:

A) liver

B) kidneys

C) bloodstream

D) lungs

Answer: A

Explanation: A) Most drug metabolism (or biotransformation) occurs in the liver, through the same biochemical pathways and reactions that affect nutrients, vitamins, and minerals. The majority of metabolism in the liver occurs through the hepatic microsomal enzyme system (P450 system). Its key component is cytochrome P450, which is actually a group of 12 enzyme families.

10) An important mechanism that affects varying drug action and metabolism is the:

A) GI tract effect

B) intestinal effect

C) first-pass effect

D) toxic drug action

Answer: C

Explanation: C) An important mechanism that affects varying drug action and metabolism is the first-pass effect. When oral drugs are absorbed from the GI tract, they move to the liver through the hepatic portal vein. Metabolism accomplishes the conversion of molecules as well as biodegradation of foreign substances.

11) The initial rate of distribution of a drug is heavily dependent on the ________ to various organs.

A) blood flow

B) hepatic portal circulation

C) oxygen distribution

D) reactions

Answer: A

Explanation: A) The initial rate of distribution of a drug is heavily dependent on the blood flow to various organs. Lipid-soluble drugs enter the CNS rapidly. Because of the blood-brain barrier, certain drugs are poorly distributed to the CNS because they pass through the barrier. The three major influencing factors related to drug distribution are: blood flow to the body tissues, how drugs are able to exit the vascular system, and how drugs are able to enter body cells.

12) Which of the following carries blood directly to the liver?

A) A biochemical pathway

B) Renal portal circulation

C) Hepatic portal circulation

D) Lymphatic portal circulation

Answer: C

Explanation: C) The hepatic portal circulation carries blood directly to the liver. If the liver has a high metabolic capacity, the drug is totally inactivated on its first pass, and no therapeutic effects occur. A drug may be given parenterally in order to avoid the first-pass effect. The liver is temporarily bypassed, and the drug reaches therapeutic levels in the systemic blood.

13) Orally administered drugs are usually absorbed in the:

A) lower GI tract

B) esophagus

C) pharynx

D) upper GI tract

Answer: D

Explanation: D) Orally administered drugs are usually absorbed in the upper GI tract (the stomach and the small intestine). From the small intestine, drugs are absorbed and immediately move to the liver for metabolism, involving various enzymes, to reach the systemic circulation. This process is called the first-pass effect.

14) The stomach has a(n) ________ environment.

A) basic

B) acidic

C) alkaline

D) physiochemical

Answer: B

Explanation: B) The stomach has an acidic environment. Lipid-soluble drugs and weak acids may be absorbed directly from the stomach. Weak bases are not normally absorbed from the site. Aspirin and other drugs that have an acidic pH are easily absorbed in the stomach's acidic environment.

15) Most drug metabolism is also referred to as:

A) glucuronidation

B) oxidation

C) biotransformation

D) conjugation

Answer: C

Explanation: C) Most drug metabolism is also referred to as biotransformation. It is the process of conversion of drugs via enzymatic actions, and may be divided into four main stages: oxidation, reduction, hydrolysis, and conjugation. Oxidation is combination with oxygen. Reduction involves the gaining of electrons. Hydrolysis is the cleaving of a compound into simpler compounds, with uptake of hydrogen and hydroxide from water molecules. Conjugation is the combination of substances with glucuronic or sulfuric acid.

16) Which of the following medications temporarily bypasses the liver?

A) Vitamin D

B) Penicillin

C) Vitamin A

D) Nitroglycerin

Answer: D

Explanation: D) Nitroglycerin temporarily bypasses the liver. It may avoid the first-pass effect via sublingual administration, since this method allows it to be absorbed directly into the systemic circulation. The drug moves to its sites of action prior to being exposed to liver enzymes.

17) For which of the following drugs may toxicity occur when blood levels of potassium are lower than normal?

A) digoxin

B) cortisol

C) tetracycline

D) morphine

Answer: A

Explanation: A) For digoxin, toxicity may occur when blood levels of potassium are lower than normal. This is a highly significant example of altered drug response due to electrolyte imbalance. Lower than normal levels of potassium may result in digoxin toxicity, and potentially fatal dysrhythmias.

18) Which of the following is NOT one of the three categories of tolerance?

A) pharmacodynamic

B) hydrophilic

C) metabolic

D) tachyphylaxis

Answer: B

Explanation: B) The term "hydrophilic" is NOT one of the three categories of tolerance. It refers to a substance that is water-soluble. The three categories of tolerance include: pharmacodynamic tolerance, metabolic tolerance, and tachyphylaxis.

19) Which of the following chemical substances in the blood normally cannot pass during glomerular filtration?

A) simple sugars

B) electrolytes

C) proteins

D) uric acids

Answer: C

Explanation: C) Proteins in the blood normally cannot pass during glomerular filtration. This process occurs at the glomerulus of the kidney tubule. Drugs are forced through pores of capillary walls, then into the tubular urine. However, blood cells and large molecules such as proteins cannot undergo this process due to their size. Therefore, drugs bound to albumin remain in the blood.

20) Manipulation of urinary pH results in decreased passive reabsorption and increased:

A) excretion

B) glomerular filtration

C) recirculation of urea

D) elimination of iron

Answer: A

Explanation: A) Manipulation of urinary pH results in decreased passive reabsorption and increased excretion. Regarding competition for active tubular transport, if two drugs are administered concurrently that both use the same transport system, excretion of each drug is delayed by the other's presence.

21) Certain drugs are poorly distributed to the CNS because they:

A) must be approved by the FDA

B) are fat soluble

C) pass through the blood-brain barrier

D) are hepatotoxic

Answer: C

Explanation: C) Certain drugs are poorly distributed to the CNS because they pass through the blood-brain barrier. This is the highly-selective permeable barrier separating the blood from the brain extracellular fluid in the CNS. It prevents entry of many undesirable chemicals.

22) The lowest amount of blood flow in solid tumors occurs because:

A) they are infected

B) they have metastasized to other organs

C) they are benign

D) there is a limitation of blood supply

Answer: D

Explanation: D) The lowest amount of blood flow in solid tumors occurs because there is a limitation of blood supply. Low regional blood flow affects drug therapy in tumors and abscesses. When a tumor is sold, the lowest amount of blood flow is in the tumor's core. High drug levels, therefore, cannot reach the deeper parts of a tumor, making solid tumors highly resistance to drug therapy.

23) Faster drug excretion via the kidneys occurs by converting:

A) lipid-soluble drugs into more water-soluble forms

B) water-soluble drugs into more lipid-soluble forms

C) the color of urine

D) urea to amino acids

Answer: A

Explanation: A) Faster drug excretion via the kidneys occurs by converting lipid-soluble drugs into more water-soluble forms. This speeds up excretion of many drugs. Methods of conversion include the structural addition of a hydroxyl group, or by glucuronidation, which is the addition of glucuronic acid to a substrate. This process is often involved in metabolism of drugs and other substances. It is also called glucuronosylation.

24) Which of the following is NOT a stage of biotransformation?

A) hydrolysis

B) fluoridation

C) oxidation

D) conjugation

Answer: B

Explanation: B) Fluoridation is NOT a stage of biotransformation. The stages of biotransformation include oxidation, reduction, hydrolysis, and conjugation. Fluoridation is defined as the addition of fluorides to the public water supply, to reduce the incidence of tooth decay.

25) End-products of a drug occur in the:

A) small intestine

B) pancreas

C) kidneys

D) liver

Answer: D

Explanation: D) End-products of a drug occur in the liver, after the drug was previously moved from the liver, through the bile duct, to the duodenum, and then moved back to the liver via the portal blood. Since the liver is the major site of drug metabolism, liver disease may result in drugs accumulating in the body.

26) Total clearance of a drug is directly affected by the:

A) dosage of the drug

B) amount of blood flow to the organs of elimination

C) age, sex, and race of the patient

D) drug plasma concentration

Answer: B

Explanation: B) Total clearance of a drug is directly affected by the amount of blood flow to the organs of elimination. The rate of drug clearance can also be significantly affected by cardiac disease, as well as drugs that alter blood flow. Also, for some drugs, clearance is not constant.

27) Peak concentration of a drug is the:

A) plasma level at which toxic effects begin to occur

B) plasma drug levels below which therapeutic effects do not occur

C) highest level at which a drug is present in the body

D) minimum effective concentration and the toxic concentration

Answer: C

Explanation: C) Peak concentration of a drug is the highest level at which it is present in the body, whereas the trough concentration is the lowest level at which a drug is present in the body.

28) A comparatively large dose given at the beginning of treatment to quickly obtain therapeutic effects is called a:

A) loading dose

B) maintenance dose

C) plateau

D) half-life

Answer: A

Explanation: A) A loading dose is a comparatively large dose given at the beginning of treatment to quickly obtain therapeutic effects. A maintenance dose keeps the plasma concentration of the drug continuously in the therapeutic range. However, the more a drug is taken, the more chance that drug accumulation will occur.

29) When patients are taking monoamine oxidase inhibitors (MAOIs), they may eat:

A) beef liver

B) ripe cheese

C) fish

D) yeast products

Answer: C

Explanation: C) When patients are taking monoamine oxidase inhibitors (MAOIs) used for depression - they may eat fish but not products such as beef liver, ripe cheese, or yeast products. This is because these foods, as well as Chianti wine, may trigger serious malignant hypertension.

30) Which of the following defines the "half-life" of a drug?

A) the time taken for it to metabolize in the liver

B) the time taken for its concentration to increase from one-half to full, after the last dose

C) the time taken for it to be excreted by the kidneys

D) the time taken for its concentration to decrease from full to one-half, after the last dose

Answer: D

Explanation: D) A drug's half-life is the time taken for its concentration to decrease from full to one-half, after the last dose. This is the major determinant of the duration of drug action. The half-life of each may be different.