Pharmkinectics Flashcards
(23 cards)
- dissolutin in stomach
- Absorption- into central compartment (duodenum-liver)
- Distributions- movement in tissue onto receptors (plasma)
- Biotranform/Metabolize - liver
- Elimination- urine bile
Five steps in time course of drug actions
Efficacy
determined by concentrate of drug at the receptor.
correlate w/ plasm drug levels
Absorbion, Distributin Elimination
LD, MD, Effect Drug concnetraion
What pharmacokinetics deals with (6 terms)
Routes of Drug Administration
IV Oral- swallow (po) Buccal- into cheek Sublingual-under tongue IM SC Inhalation- naxalone Transdermal-pathc Topical Rectal Intrthecal- spinal cord
ClearanceCL
Types of clearance
FActors the predict ratel of elimination
Mostly liver and kidney responsible for CL
Liver_lipid to water__now_kidney can clear__urine
Vol of fluid that would be cleared by drug/time
Fraction of unchanged drug reach plasm following admin of route of drug
IV F= 100%
Po F=5+%
Bioavailability F
Area under the curve AUC
F=AUC. AUC PO/AUC/IV dose
F IV= 100%
Drug exposure
Extent of absorbtion
First pass effect
portal blood system_liver 1st_ before entry into systemic circulation.
most of rx elimintated(depends on perfusion through organ
High isoniazid, morphin propanaol, verapamil, TCA
Rectal, sublinual, transdermal
Cocaine- if swallowed goes thru 1st pass. no brain, why snorts
assumption that ther is target concentrion for max effect which correlates to Cp (drug plasma levels)
Rational dosage regimens
Maintenance dose definition
does in should = dose out
does rate/F
Dose rate=Cl/Hr/Wt x target plasma [}
Dose rate/F
Cp does not correlates to therapeutic efficay and toxcity
Measure toxicity
Dose not related to efficacy
Lab will not do labs on TW 1-1000, impossible to OD
Monitor compliance
Change in cl rate d/t kidney or liver failure
Change in Vd d/t fluid, edem, acistes
half life change d/t age
Drug interaction
Therapeutic Drug Monitoring (TDM)
TDM what drugs to measure
low TI (digoxin) .5-2.0 Chonically used no s/s of toxictiy bio effects not easily measured Helps determine Target concentration Revise based on Cp
Passage of drugs across membranes (8 terms)
Ionized drugs (most drugs, water soluble) depend on ph environment. DO NoT cross membrane
Lipid soluble cross membrane-sone
Non IOn- lipid soluble- non polar, neutral
pka high for BASE
pKa low for ACID
Stomach PH 2, no absorbtion
Duondenum major site absorbtion
Drug absorption from stomach
Volume of distributionVd
concentration of drug in body/ {} of drug in Plasma
volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.
Vd given
Plasm{} labs provide
Low Vd L means excreted in body, never entered organ, water soluble
5- only in plasma
5-20 ECF
20-40 total bodily fluid
>40 in deep tissue, lipid soluble
Which has greater pentration to deep tissue?
Zero-constant amount of drug elimnated/unit-OD. Constant amt eliminated regardless of ingestion
0 order- aspirin, phenytoin, ethanol
10mg/ 1hr only
Start with 50g
1hr 40, 2hr 30
1/2 dependent on {drug}
Enzymes needed, often not enough enzyme, more drug
REst RX- 1st- more drug in plasma= more drug in urine constant 1/2 life 2mg/hr 4mg/ 2hr 6mg/3rd hr ec.
Zero order vs First order
Half Lifet1/2
Time it takes to eliminate 1/2 of drug. Time to lower {drug} by half
1hr is half life
100-0
50mg= 1hr-1 half life
25-hr= 2hr-2 half life
Rate of elmination deteremined by concentration
RX- 4-5 1/2 lives elapse b4 full effect of drug
Creatinine clearance (CC)
used for rX 100% cleared by kidney (also liver)
If kidney damage, drug stays in body= toxicity
((140-age) x (kg)/ Serum Cp (given) x 72) x .85 W, 1 M
As a rule of thumb 100
Creatine related body wt and muscle mass, produced daily, constant.
filtered by glomerous no absorbtion
measure GFR
F- 72-110 M 94-140 100mL/min avg ** Renal Fx Slight 52-63 Mild 42-52 Marked <28
Reference Interval (concept and usage)
Calculation of dose adjustment using the CC
How much still in, is person coming out of this
1/2 life given
{}in plasma=Cp from lab ( volume distribution)
Plasma Serum
Water+ clotting factors
Water- minus clotting factors
Compartments (organ)
Central compartment
Tetracylceine
any drug stoargage:
ICS
ECS (space fluid),
fat stores,
bone (lead 90% in bone 6y 1/2life, tetracyclin)
Blood- route to all tissue, cenral compartment
Sequestered
constant amount of drug eliminated per time
Aspirin
Phenytoin
Ethanol
