Basic Principles of Pharmacology V

Question 1

Kinetic compartments

Answer 1

• the fluid space containing the drug
• useful for the mathematical calculations
• view the complete body as one or two compartments for simplicity

Question 2

Molecular Equilibria and the Single Dose Response curve

Answer 2

• site of administration really high blood concentration and then a little bit in plasma and receptors and then plasma and just a little of elimination
• site of administration starts spreading out until some starts getting eliminated
• then it eventually gets all the way to elimination

Question 3

Absorption Kinetics

Answer 3

-absorption rates are related to the transport processes involved, either zero order (carrier mediated with saturated carrier protein at Vmax- not sensitive to drug concentration) or first order- (sensitive to drug concentration)

Question 4

Zero Order Rate Absorption

Answer 4

• disappearance from site of administration
• Ct= kat- an amount per unit time
• when ct=concentration of a drug in volume of distribution (vd), of single kinetic compartment, after time t, for zero order absorption
• the size of the dose does not change absorption
• ka might be fast or slow but is constant
• a large dose of drug could saturate a carrier for facilitated diffusion or constant IV infusion of a dose of a drug

Question 5

First order absorption rate

Answer 5

• proportional to the amount of drug present
• ct= M/Vd (1-e^-kat)
• a proportion per unit time
• oral absorption of lipid soluble drug
• with time we approach a maximum amount absorbed that hopefully equals most of the dose
• the larger the dose, the faster the concentration rises in the compartment

Question 6

Elimination Kinetics

Answer 6

• Cl= Clmet + Clrenal
• a rate limiting step determines the rate of elimination
• independent of drug concentration occurs if the rate limiting step: 1) is insensitive to drug concentration or 2) is saturated

Question 7

Zero Order Elimination

Answer 7

• an amount per unit time
• Ct= Co - ket
• saturated at vmax
• ethanol

Question 8

First Order Elimination

Answer 8

• a proportion per unit time
• log Ct = log Co -kt/2.303
• log paper and straight line= first order elimination
• collander
• half life only for 1st order process
• always reproducible

Question 9

Half life

Answer 9

• t1/2= 0.693/ke

- formula for half-life of a drug in plasma when elimination rate obeys first order kinetics

Question 10

Relationship of Volume of Distibution, Clearance and Half Life

Answer 10

• Cl= Vd x ke
• since t1/2 =0.693/ke
• t1/2= 0.693Vd/Cl
• a decrease in clearance from renal or hepatic failure will increase t1/2