Pharm: Pharmacokinetics 2

Question 1

What are the 4 physical factors that influence drug absorption?

Answer 1

1. Blood flow to the absorption site
2. Total surface area available for absorption
3. Contact time at the absorption site
4. P-glycoprotein: ATP-dependent efflux pump

Question 2

What can shock reduce that affects drug absorption from subcutaneous administration?

Answer 2

Blood flow, which can minimize absorption.

Question 3

What does increased surface area lead to in terms of drug absorption?

Answer 3

Increased absorption.

Question 4

How does the speed of a drug’s movement through the GI tract affect its absorption?

Answer 4

The faster a drug moves through the GI tract, the less it is absorbed.

Question 5

How does diarrhea impact drug absorption?

Answer 5

Causes reduced absorption because the drug moves faster through the GI tract.

Question 6

What is bioavailability?

Answer 6

The rate and extent to which an administered drug reaches systemic circulation.

Question 7

What is bioavailability?

Answer 7

The administered dose that reaches systemic circulation.

Question 8

What is the bioavailability (F) of drugs given IV?

Answer 8

100%.

Question 9

If 100 mg of a drug is administered orally and 70 mg is absorbed, what is the bioavailability?

Answer 9

70%.

Question 10

What are the 3 factors that influence bioavailability?

Answer 10

1. First-pass hepatic metabolism
2. Solubility of drug
3. Chemical instability

Question 11

How does first-pass metabolism impact bioavailability?

Answer 11

Causes a decrease in F.

Question 12

What is the bioavailability of hydrophilic drugs?

Answer 12

Low.

Question 13

What are the two compartments involved in drug absorption?

Answer 13

1. Compartment 1 is where the drug is placed
2. Compartment 2 is movement into the blood.

Question 14

Does IV administration involve absorption?

Answer 14

No.

Question 15

What is lag time?

Answer 15

The time from administration to appearance in blood.

Question 16

What is MEC?

Answer 16

Minimum effective concentration, the amount of drug required to produce a therapeutic effect.

Question 17

What is the onset of activity?

Answer 17

The time from administration to reaching MEC.

Question 18

What is the duration of action?

Answer 18

The time plasma concentration remains above MEC.

Question 19

What happens to pH when taking Tums or Pepto-Bismol?

Answer 19

pH would increase due to the antacid.

Question 20

What happens to the absorption of a weak acid drug like Amoxicillin when taking Tums or Pepto-Bismol?

Answer 20

Absorption of amoxicillin would decrease because pH was increased due to Tums or Pepto.

Question 21

What happens to the plasma level curve graph when taking a weak acid drug like Amoxicillin with Tums or Pepto-Bismol?

Answer 21

Plasma level curve would move to the right and be smaller (not reach peak).

Question 22

What happens to the absorption of a weak base drug like Amphetamines when taking Tums or Pepto-Bismol?

Answer 22

Absorption of amphetamines would be increased due to pH becoming more basic.

Question 23

What happens to the plasma level curve graph when taking a weak base drug like Amphetamines with Tums or Pepto-Bismol?

Answer 23

Plasma level curve graph would move to the left and become ‘larger’ (higher peak) while reaching the MEC quicker.

Question 24

What should be done with a drug’s dose in renal dysfunction?

Answer 24

Lower it because elimination of the drug is worse.

Question 25

What are the 4 things that determine the distribution of a drug?

Answer 25

1. Size of the organ 2. Cardiac output and local blood flow 3. Capillary permeability 4. Hydrophobic vs. hydrophilic nature of drug.

Question 26

How does albumin impact the volume of distribution?

Answer 26

Albumin is the primary binding protein and is an inert binding site that inactivates the drug when it binds.

Question 27

What happens to bound drugs in relation to pharmacological activity?

Answer 27

Bound drugs are pharmacologically inactive, thus albumin lowers effective concentration of free drug and decreases rate of transport to other sites = need higher dose.

Question 28

What are the water compartments of the body and their volumes in a 70 kg individual?

Answer 28

Plasma compartment = 4L Extracellular fluid = 14 L Total body water = 42 L.

Question 29

What does Vd relate to?

Answer 29

The amount of drug in the body to the plasma concentration of the drug.

Question 30

What is the equation for Vd?

Answer 30

Vd = amount of drug in body / plasma drug concentration or Total amt of drug / Cp.

Question 31

What is the relationship between Vd and Cp?

Answer 31

Vd and Cp have an inverse relationship.

Question 32

What does a higher Vd indicate?

Answer 32

More drug moving into the extravascular compartments.

Question 33

If a total amount of drug in the body is 20 mg and the concentration in the plasma is 2 mg/L, what is the Volume of distribution?

Answer 33

10 L (20/2) and the drug will reside in interstitial volume/extravascular compartments.

Question 34

What are the units for Vd?

Answer 34

Liters (L).

Question 35

If a total amount of drug in the body is 20 mg and the concentration in the plasma is 18 mg/L, what is the Volume of distribution?

Answer 35

1.1 L (20/18) and the drug will reside mostly in the plasma/vascular compartment.

Question 36

If a total amount of drug in the body is 200 mg and the concentration in the plasma is 2 mg/L, what is the Volume of distribution?

Answer 36

100 L (200/2) and the drug will reside in extravascular compartments.

Question 37

Can Vd be larger than the volume of the body? Why or why not?

Answer 37

Yes, if a drug is given in large doses and rapidly leaves the vascular compartment.

Question 38

What is the constant fraction of drug being eliminated over time?

Answer 38

Elimination.

Question 39

What are the 2 parts to the elimination phase?

Answer 39

1. Biotransformation 2. Excretion.

Question 40

What is the Vd equation and its units?

Answer 40

Vd = amt in mg / Cp in mg/L.

Question 41

If a drug has a Vd of 25 L and you desire a plasma concentration of 1 mg/L, what amount of drug would you give?

Answer 41

25 mg.

Question 42

What is the formula relating Vd and dose?

Answer 42

Vd x Cp = dose.

Question 43

If a cardiac patient with arrhythmia needs to increase digoxin levels from 1 ug/L to 3 ug/L with a Vd of 440 L, how much additional drug should be given?

Answer 43

880 ug.

Question 44

What does a large Vd indicate about the location of most of the drug?

Answer 44

Most of the drug is outside the plasma.

Question 45

What effect can a factor that increases Vd have on half-life?

Answer 45

Increase.

Question 46

What are the 4 drug reservoirs?

Answer 46

1. Plasma proteins 2. Cellular reservoirs 3. Fat 4. Bone.

Question 47

Most drugs are bound to what?

Answer 47

Plasma proteins.

Question 48

Acidic drugs bind to which protein?

Answer 48

Albumin.

Question 49

Basic drugs bind to which protein?

Answer 49

Alpha 1 acidic glycoprotein.

Question 50

What is the pharmacological activity of bound drugs?

Answer 50

Bound drugs are pharmacologically inactive.

Question 51

How do drugs cross the placenta?

Answer 51

Primarily by simple diffusion.

Question 52

What type of drugs readily enter the fetal blood from the maternal circulation?

Answer 52

Lipid-soluble.

Question 53

What molecules cross the BBB?

Answer 53

Lipophilic and very small molecules.

Question 54

If a patient weighs 60 kg and the dose of drug is 1000 mg with Cp at 2 mg/L, what is the Vd in L/kg?

Answer 54

Vd = 500 L; 500 L / 60 kg = 8.333 L/kg.

Question 55

If Cp is 20 mg/L and Vd is 0.3 L/kg, what is the dose for a patient weighing 60 kg?

Answer 55

Dose = 18 L x 20 mg/L = 360 mg.