Pharmacokinetics
describe the 4 characteristics of the bioavailability factor (F)?
-the dosage form (tablet, capsule, etc.) -the route of administration (IV, subQ, IM, oral, etc.) -the extent of "First Pass" metabolism (intestines, liver, etc.) -the absorption properties of the drug (lipophilic, ionic, size, etc.) *note that the bioavailability factor does NOT take into account the MASS of the active ingredient.
equations to know to solve problems:
1) Amount of Absorbed Drug = F x (Amount of Administered Dose) 2) C = C₀ e ^ -kt (you must be able to solve for time t) 3) t₁/₂ = ln2/k = 0.693/k 4) C = (SFD/Vd)(e^-[Cl/Vd)t]) (you must be able to solve this equation for the clearance Cl) 5) k = Cl/Vd 6) C₀ = SFD/Vd
Absorbed dose = F x D what is F & D?
absorbed dose = F (bioavailability factor) x D (administered dose)
In terms of this equation: C=(SFD/Vd)(e^-[Cl/Vd)t]): While D is the amount of drug that is _____, SFD is the amount of drug that is actually ______ into the circulation.
administered; absorbed
in the integrated rate equation, what does this term represent? [S F D₀/Vd]
administration + absorption + distribution
in the integrated rate equation, what does this term represent? e^-kt
elimination (metabolism + excretion)
A larger clearance Cl leads to a ______ rate, and so C decreases ______ with time and this is reflected in Cl being in the numerator of the exponential function.
faster; faster *and vice versa: a smaller clearance Cl leads to a slow rate, and so C decreases slower with time.
The Volume of Distribution (Vd) gives us a ______ sense to the extent of distribution of a drug, but it cannot tell us _____ where a drug went.
general; exactly
what is the formula that represents the relationship between the clearance and the elimination rate constant?
k = Cl/Vd *know how to preform calculations using 2/3 values, and solving for the 3rd.
In terms of this equation: C=(SFD/Vd)(e^-[Cl/Vd)t]): in the equation, elimination is represented by the actual _____, embodied by the (e^-[Cl/Vd)t]) term, which explicitly includes the ____ dependency of the elimination process.
kinetics; time
A larger volume of distribution leads to a _____ C₀ and therefore ____ a lower C.
lower; initially
a larger volume of distribution in the exponential function leads to a _____ rate, so C decreases ______ with time, and this is reflected in Vd being in the denominator of the exponential function.
slower; faster *and vice versa: a smaller volume of distribution (Vd) in the exponential function leads to a faster rate, and so C decreases slower with time.
The effect of Vd on C is much _____ in the first linear term (SFD/V) than the effect of Vd on C in the second exponential term (e^-[Cl/Vd)t]), because the second term changes MUCH ______ than the first term for a given value of Vd.
smaller; faster
What is the bioavailability factor (F)?
the measure of the percentage or fraction of the administered dose that reaches the systemic circulation of the patient
The Volume of Distribution (Vd) formal definition
the size of a compartment necessary to account for the total amount of drug in the body if it were present throughout the body at the same concentration found in plasma *plays a role in determining BOTH the distribution (initial concentration-C₀) and the elimination of drug.
What is the formal definition of the Clearance (Cl)?
the volume of plasma cleared of drug per unit time by the processes of elimination (metabolism and excretion) *represents the efficiency of the organs of elimination such as the liver and the kidneys.
In terms of this equation: C=(SFD/Vd)(e^-[Cl/Vd)t]): the equation describes the distribution of the drug, embodied in the volume of distribution term Vd. Specifically it describes the extent of the distribution but not the ______ of distribution.
KINETICS
the integrated rate equation is descriptive of administration, absorption, distribution, and elimination even though we only treat the ______ of ______.
KINETICS; ELIMINATION
The Salt Factor S represents the actual _____ of the active ingredient
MASS
