Download Tom Hsiung, BS Pharm

Summary of Pharmacokinetics Core Equations
Tom Hsiung, B.S. Pharm
Amount of Drug Absorbed or
Raching the Systemic Circulation = (𝑺)(𝑭)(𝑫𝒐𝒔𝒆)
F: Bioavailability factor
S: Fraction of the administered dose that is the active drug.
Administration Rate RA =
(𝑺)(𝑭)(𝑫𝒐𝒔𝒆)
𝝉
RA: The administration rate is the average rate at which absorbed drug
reaches the systemic circulation.
τ: Dosing interval
The Fraction of Free Drug Concentration or 𝐟𝐮 =
𝑪 𝒇𝒓𝒆𝒆
𝑪 𝒃𝒐𝒖𝒏𝒅+𝑪 𝒇𝒓𝒆𝒆
Fraction of Unbound
C free: Serum concentration of free or unbound drug
C bound: Serum concentration of bound drug
Low Plasma Protein Concentrations
𝑪𝑵𝒐𝒓𝒎𝒂𝒍 𝑩𝒊𝒏𝒅𝒊𝒏𝒈 =
𝑪′
(𝟏 − 𝒇𝒖) [
𝑷′
+ 𝒇𝒖
𝑷𝑵𝑳 ]
CNormal Binding: The plasma drug concentration that would be expected if the
1/3
patient’s plasma protein concentration were normal.
PNL: The normal plasma protein. An average normal albumin
concentration is 4.4 g/dL (range: 3.5 to 5.5 g/dL).
C’: The patient’s plasma drug concentration
P’: The patient’s plasma protein concentration
fu: Fraction of free drug concentration or fraction of unbound
Loading Dose =
(𝑽)(𝑪)
(𝑺)(𝑭)
V: The volume of distribution
C: The desired plasma level
Incremental Loading Dose =
(𝑽)(𝑪𝒅𝒆𝒔𝒊𝒓𝒆𝒅 −𝑪𝒊𝒏𝒊𝒕𝒊𝒂𝒍)
(𝑺)(𝑭)
Incremental Loading Dose: The additional loading dose that will be
required to achieve a higher plasma concentration (Cdesired) than the
present concentration (Cinitial).
Clearance Cl =
(𝑺)(𝑭)(𝑫𝒐𝒔𝒆/𝝉)
𝑪𝒔𝒔 𝒂𝒗𝒆
Cl: Clearance represents the theoretical volume of blood or plasma which
is completely cleard of drug in a given period.
Css ave: The average steady-state drug concentration
τ: Dosing interval
2/3
Maintence Dose =
3/3
(𝑪𝒍)(𝑪𝒔𝒔 𝒂𝒗𝒆)(𝝉)
(𝑺)(𝑭)