Week 1 (Quiz 1) Flashcards
PK
Behavior of drugs in the body (ADME- absorption, distribution, metabolism, elimination); based on analysis of plasma concentration of drug over time
Bioavalibility of IV and IA
100%
Volume of distribution formula
Vd = Ab/Cp
If Vd is large…
Wide distribution outside of plasma
If Vd is small..
Drug distributes more to extracellular fluid, including plasma
5 Factors influencing absorption/distribution
- differing characteristics of body tissues
- Disease states that alter normal physiology
- Lipid/water solubility of the drug
- Regional differences in physiologic pH
- Extent of protein binding
pK equation for weak acids
pH = pKa + log(A-/HA)
pK equation for weak bases
pH = pKa + log (B/HB+)
Examples of weak acids
phenobarbital, salicylic acid, methotrexate
Weak acids are trapped in:
alkaline environment
Overdose treatment for weak acids
sodium bicarbonate + diuretic
Examples of weak bases:
amphetamines, cocaine, strychnine, quinidine
Weak bases are trapped in:
acidic environment
Overdose treatment for weak bases:
ammonium chloride or ascorbic acid
Clearance equation
Cl = Vd x Ke
Zero-order kinetics
rate is independent of plasma concentration of the drug
First-order kinetics
rate is dependent on plasma concentration of drug, also means constant fraction of drug appears or disappears per unit time.
Rate of elimination equation
-Ke x Cp
Half-life equation
t1/2 = 0.693 xVd/Cl
input rate equation
Css x Cl
Steady state kinetics dogma 1
Steady-state concentration is only dependent on rate of administration and rate of elimination
Steady state kinetics dogma 2
Time to achieve steady state is 4-5 half-lives
Maintenance dose equation
MD = Css x Vd x Ke
Loading dose equation
LD = Vd x Css