Pharmacokinetics Flashcards
What are the equations for clearance?
Cl = Dose/AUC (AUC of a concentration/time graph of an IV bolus dose)
Cl = Q x ER
Cl = Vd x K
Cl = Vd/t (t = time constant)
What are the equations for rate of elimination?
Relim = Concentration x Clearance
Relim = VD x K
Volume of distribution
VD = Dose / Co
Where Co is the concentration at time 0
What is the equation to find the loading dose for a single compartment model?
Loading dose = VD x C
where VD is volume of distribution and C is desired plasma concentration
What is the equation for the infusion rate required for a single compartment model?
Rate inf = C x CL
Where C = concentration and CL is the clearance
What are the equations for the time constant?
t = 1 / K
t = VD/Cl
What is the equation for Half life for a zero order reaction?
T 1/2 = Co/2K
Where Co is the concentration at time 0 and K is the rate constant of elimination
What are the equations for half life for first order reactions?
t1/2 = 0.693/K
t1/2 = 0.693T
or
t1/2 = 0.693(VD/CL)
Where T = time constant
Define volume of distribution
The apparent volume into which a drug disperses to explain the observed plasma concentration at time t=0.
Define time constant
The time it takes plasma concentration to fall to 1/e of its current value (37% of its current value)
OR
The time it would have taken the plasma concentration to fall to zero had the initial rate of decline continued.
Define half life
The time it takes for plasma concentration to fall to half of its current value
t1/2 = ln2.T
(T = time constant)
Define the rate constant for elimination
The inverse of the time constant
The fractional volume eliminated in unit time
Define clearance
The volume of blood from which drug is completely removed per unit time.
The product of volume of distribution and rate constant for elimination (Vd x K)
The ratio of volume of distribution to time constant (Vd/T)
