Pharm 1 Flashcards
A drug with a Vd that exceeds TBW is assumed to be lipophilic or hydrophilic? Do you need more or less of the drug?
Lipophilic
Need more of the drug to achieve a given plasma concentration
Ex: of lipophilic drugs?
Propofol
Ex: of hydrophilic drugs?
NMB
A dug with a Vd less than TBW or <42L is assumed to be lipophilic or hydrophilic?
Hydrophilic
(need less of the drug)
Clearance is directly proportional to ?
Blood flow to organ
Extraction ratio
Drug dose
Clearance is inversely proportional to ?
Half life
Drug concentration in the central compartment
What is steady state?
Rate of administration = rate of elimination
Creates a stable plasma concentration
Steady state is achieved after how many half-lives?
5
Two compartment model photo
Elimination Half-time vs Half-life
Half-time; Amount of time for 50% to be removed from the plasma
Half-life; Amount of time for 50% to be removed from the body
How many half lives till we say the drug is eliminated from the body? What percentage of the drug is gone?
5 half times
96.9% of the drug is eliminated
What is context sensitive half time?
Takes into account the duration of the infusion of the drug. The amount of time after the infusion is stopped to decline by 50%
What two factors determine the extent of ionization?
pKa of the drug
pH of the solution
What is pKa?
50% of the drug is ionized and 50% of the drug is unionized
Are ionized drugs or unionized drugs more likely to be renally excreted? What about cross the BBB?
ionized drugs are more likely to be excreted from the kidneys
Non-ionized drugs cross the BBB
What is fetal ion trapping?
A non-ionized drug crosses the placenta and reacts with the slightly more acidic fetal pH and becomes ionized. This traps the drug in the placenta with baby.
Is mom or baby more acidotic?
Fetal pH is slightly lower
Do highly protein bounds drugs have slower or faster elimination?
Slower elimination
How is the volume of distribution affected when plasma protein binding increases?
The Vd decreases because more of the drug is bound to albumin
What does hepatic extraction ratio measure?
How much the drug is delivered to the liver vs how much is eliminated by the liver
What does a hepatic extraction ratio of 0.5 mean? 1.0?
50% of the drug is eliminated that is delivered to the liver
100% of the drug is eliminated
Which drugs undergo Hoffman elimination?
Cisatracurium
Atracurium
Which drugs undergo alkaline phosphatase elimination?
Fospropofol
