6: Basic Priciples VI

Question 1

Steady state is attained at about ______ half lives, & time to steady state is ______ of dosage, but is dependent upon the clearance capacity of the individual.

Note that @ SS, the rate of absorption is equal to the rate of elimination.

Answer 1

Steady state is attained at about four half lives, & time to steady state is INDEPENDENT of dosage but is dependent upon the clearance capacity of the individual.

Note that @ SS, the rate of absorption is equal to the rate of elimination.

Question 2

? = 0.693Vd/Cl

Answer 2

t1/2 = 0.693Vd/Cl

Question 3

We give ______ doses when the dose interval is greater than the half life.

We give ______ individual doses when the dose interval is less than or equal to t1/2.

Answer 3

We give single doses when the dose interval is greater than the half life.

We give repeat individual doses when the dose interval is less than or equal to t1/2.

Dose interval is the frequency of intermittent drug administration, based on the drug’s half-life.

Question 4

Multiply the concentration of the drug at the first half life by ______ to get concentration at steady state.

Answer 4

Multiply the concentration of the drug at the first half life by two to get concentration at steady state.

Question 5

For emergencies, we give ______ doses to get us to immediate therapeutic concentrations first.

______ infusions get us to steady state.

Answer 5

For emergencies, we give loading doses to get us to immediate therapeutic concentrations first.

Maintenance infusions get us to steady state.

Question 6

Loading Dose = ?

Answer 6

Loading Dose = Cp x Vd

Question 7

Therapeutic Index

TI = ?

Answer 7

TI = TD50/ ED50

Therapeutic Index = Toxic Dose50/ Therapeutic Dose50

ED50 - Effective dose in 50% of the population

TD50 - Toxic dose in 50% of the population

Question 8

Margin of Safety = ?

Answer 8

Margin of Safety = TD50 - ED50

ED50 - Effective dose in 50% of the population

TD50 - Toxic dose in 50% of the population

Question 9

For newborns:

Give ______ loading dose cause their total body water is a greater proportion than in the adult.

We give ______ maintenance doses since their half life is ______

Elimination (b-phase) ______ compared with distribution (a-phase)

______ apparent volume of distribution in neonates.

Answer 9

For newborns:

Give higher loading dose cause their total body water is a greater proportion than in the adult.

We give lower maintenance doses since their half life is higher***

Elimination (b-phase) prolonged compared with distribution (a-phase)

Increased apparent volume of distribution in neonates.