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COM: Neuro II (Exam I) > Pharmacokinetics > Flashcards

Flashcards in Pharmacokinetics Deck (32):

What are the 3 time allotments considered for routes of administration?

Time for dissolution (if solid formulation)
Time for absorption (considered 0 time for IV)
Time for circulation (to site of action/onset of action)


What are the 2 routes of passive (simple) absorption?

Filtration = through pores or channels; determined y osmotic/hydrostatic pressure differential

Diffusion = through cell membranes; determined y concentration gradient


What method of absorption is most commonly utilized by drugs?

Passive diffusion (through cell membranes y concentration gradient)


What is the difference between an ionized and unionized drug?

Ionized = charged/polar

Unionized = uncharged/nonpolar


What are the characteristics of ionized vs unionized compounds in terms of lipid solubility and PM diffusion?

Ionized compounds = lower lipid solubility and do not easily diffuse across PM

Unionized compounds = higher lipid solubility and easily diffuse across PM


Ionization status of drugs depends on 2 factors. What are they?

pKa of medication
PH of membrane gradient


Define pH versus pKa

PH = measure of acidity of a soln (0-14) and is a fnx of the amt of H+ in soln

PKa = propensity of a compound to donate (acids) or accept (bases) a proton


There are 2 important areas of the body where pH varies and commonly impacts ionization status. What are these 2 locations

GI tract


When is there a 50%:50% ratio of ionized:unionized drug in the body?

When pKa = pH


Differentiate between ionized and unionized drugs in terms of absorption and elimination

HIghly ionized drugs DO NOT get readily absorbed and ARE eliminated

Highly unionized drugs DO readily get absorbed and are NOT eliminated


Facilitated diffusion is considered active transport but is unique. What are the unique characteristics of facilitated diffusion?

- does not require energy
- does not proceed against gradients


What does the alpha represent in bound/unbound fraction of a drug?

Represents the unbound fraction

**Alpha is opposite of percent protein bound


Differentiate between bound and unbound drugs

Unbound = free drug; this is active -> represented by alpha; low protein binding means low displacement

Bound = inactive drug


Explain the naming of CYPs

Family = first number
Subfamily = letter
Individual = last number


List the main sites of action of the cytochrome P450 enzyme system

GI tract


What are the 3 main processes of renal elimination?

1. Passive glomerular filtration -> blood flow dependent

2. Passive tubular diffusion -> PCT or DCT, ionization & concentration status dependent

3. Active tubular secretion -> weak acids/bases secreted into PCT


Explain first order kinetics

- the percentage of the total amount of change in the plasma concentration remains constant over time

$100 - 1/2 = 50 - 1/2 = 25...


Explain zero order kinetics

- the percentage of the total amount of change in the plasma concentration is not constant over time
- saturable (Vmax)

100-50 = 50 - 50 = 0 -> lose the same amount every time instead of a proportional loss


What does Tmax stand for?

Time at Cmax


What does MEC vs MTC stand for?

MEC = minimum effective concentration

MTC = maximum therapeutic concentration


What does F stand for in terms of absorption?

Bioavailability -> represents the fraction oof a dose that enters circulation

- describes the extend of absorption NOT the rate of absorption
- always considered 100% (F=1) for IV route
- no units


What factors determine the bioavailability of a drug?

Ionizing status in various locations
First pass and GI metabolism
Dissolution -> extend vs rate


What does S stand for in terms of absorption?

Salt factor -> percentage of a dose that equals the primary serum-assessed drug

- no units


What are the 3 items that determine the amount of drug absorbed?

Bioavailability (F)
Salt factor (S)


What is the equation for ideal body weight (IBW)?

Female = 45kg + (2.3kg X (height in inches - 60”))

Male = same but base weight of 50kg


What is the adjusted body weight (AdjBW) equation?

(0.4 X (ABW - IBW)) + IBW

**Used for ABW >40% higher than IBW


What does Cpss stand for. In terms of elimination?

Steady state -> represents an equilibrium between drug administration and body clearance, where rate in = rate out

- units = w/v #’s
- related to dose, Cl, Kel and T1/2


What is the equation used to calculate the loading dose and what are the units of the answer?

LD = ((Vd)(Cp)) / ((S)(F))

Units = weight units


What equation do you use to calculate a supplemental loading dose (LDsuppl) and what are the units of the answer?

LDsuppl = ((Vd)(Cpd - CPI) / (S)(F))

Units = weight units


What is the equation used to calculate the maintenance dose (MD)?

((Cl)(Cp)(tau)) / ((S)(F))


What is the equation used to calculate the elimination rate constant (Kel)?



((Ln(Cpt1) - ln(Cpt2)) / (T2-T1)


What is the equation used to calculate creatinine clearance (eGFR)?

[((140-age) X IBW(in kg)) / (72 X SCr)]

** multiply 0.85 if pt is female

**just simply 140-age is a good guess of eGFR so try to eliminate some answers using this