TBL 4 - Pharmacokinetics

Question 1

What treatment should be given for an overdose of a weak acid (aspirin, phenobarbitone) and what is the effect?

Answer 1

NaHCo3 alkalinizes the urine.

Question 2

What treatment should be given for an overdose of a weak base (amphetamine) and what is the effect?

Answer 2

NH4Cl acidifies the urine.

Question 3

Where are weak acids absorbed?

Answer 3

Stomach

Question 4

Where are weak bases absorbed?

Answer 4

Intestines

Question 5

What is the equation for volume of distribution (Vd)?

Answer 5

Vd = Dose/Concentration

Question 6

What does a high Vd mean?

Answer 6

Drugs with a high Vd will bind tightly in tissues and will have a higher concentration in tissues compared to the vascular compartment.

Question 7

What does a low Vd mean?

Answer 7

Drugs with a low Vd will be retained within the vascular compartment.

Question 8

What is the volume of the different compartments of the body (plasma, EC fluid, and IC fluid)?

Answer 8

Plasma: 4L
EC fluid: 14L
IC fluid: 28L

Total: 42L

Question 9

What is P-glycoprotein and what does it do?

Answer 9

Is an efflux pump that opposes the distribution of drugs to tissues, leading to drug resistance.

Question 10

What is the equation for loading dose?

Answer 10

LD = (Volume of Distribution)(Steady state Concentration)/Bioavailability

LD= (Vd)(Css)/F

Question 11

What is included in Phase I of Metabolism of Drugs?

Answer 11

Oxidation, Reduction, and Hydrolysis

Question 12

What are some examples of CYP450 Inducers?

Answer 12

Carbamazepine, Phenobarbitone, Phenytoin, Primidone, Rifampin, Chronic Alc, Glucocorticoids, St. John’s Wort, Nevirapine, and Griseofulvin

Question 13

What are some examples of CYP450 Inhibitors?

Answer 13

Macrolides, Doxycycline, Sulfonamides, Cimetidine, Disulfiram, Grapefruit Juice, Itraconazole and Ketoconazole, Ritonavir, Ciproflaxcin, Amiodarone, Sulfonamide, Omeprazole, and Valproate.

Question 14

What is included in Phase II of Metabolism of Drugs?

Answer 14

Conjugation with acetate, glucuronate, sulfate, or glycine.

Occurs in the cytosol

Question 15

What is the equation for clearance?

Answer 15

CL=volume of distribution/k

CL=Vd/k

k = 0.7/t1/2

Question 16

What is the equation for maintenance dose?

Answer 16

MD = (Clearance)(Steady state Concentration)(time interval)/bioavailability

MD = (CL)(Css)(t)/F

Question 17

What is the equation for infusion rate?

Answer 17

Ko = (Steady state concentration)(clearance)

Ko = (Css)(CL)

Question 18

What is the equation for the half life of a drug?

Answer 18

t1/2 = (0.7)(volume of distribution)/clearance

t1/2 = (0.7)(Vd)/(CL)

Question 19

What is the equation for loading dose?

Answer 19

LD=(volume of distribution)(concentration in plasma)/bioavailability

LD=(Vd)(Cp)/F

Question 20

Describe first order elimination.

Answer 20

The rate of drug elimination is proportional to plasma drug concentration at any given time.

A constant fraction of drug is eliminated per time.

Question 21

Describe zero order elimination.

Answer 21

Constant or fixed amount of drug is eliminated per time, regardless of concentration.

Saturable.

Role of elimination is not affected by the serum concentration of the drug.

Ex: phenytoin, ethanol, aspirin