Pharmacokinetics

Question 1

Definition of pharmacokinetics

Answer 1

What the body does to the drug

Question 2

ADME

Answer 2

Absorption
Distribution
Metabolism
Excretion

Question 3

Absorption

Answer 3

oral, SC/IM, IV
Medication into the blood
Dependent on:
- lipophilicity
More lipid soluble = more easily passes through lipid bilayer of cell membrane
- acidity of GIT

Question 4

Distribution

Answer 4

systemic drug travels to muscles, skin, bones, organs, etc
Dependent on:
- circulation
- age
- permeability of cell membrane (lipophilicity)
- plasma protein binding

Question 5

Metabolism

Answer 5

Main site is the liver
1st pass metabolism (high = alt route required)
Dependent on:
- age
- genetics (enzymes)
- type of medication
- nutrition / GIT

Question 6

Excretion

Answer 6

Kidneys
Removal of chemically active / inactive or unchanged metabolites
Dependent on:
- age
- GFR
- type of drug

Question 7

Liberation

Answer 7

solid disintegration / dissolution / permeation

Question 8

Bioavailability

Answer 8

Extent of absorption
Fraction of administered dose into bloodstream

Incomplete = unable to cross GIT, breakdown, 1st pass metabolism in GIT /liver, failure to disintegrate

Question 9

Volume of distribution

Answer 9

VD

VD = dose / Cp (drug plasma conc)

Small = drug in blood
Big = drug in tissue

Question 10

Narrow Therapeutic Index

Answer 10

smaller range of dose to give optimal clinical effect

Question 11

P1 metabolism

Answer 11

oxidation
hydrolysis
reduction

CYP P450 enzymes (34A)
- inhibit
- induce
- substrate

Question 12

CYP inhibitors

Answer 12

SICKFACES.COM GAVID

Sodium Valproate
Isonazid
Cimetidine
Ketoconazole
Fluconazole
Amiodarone
Chloramphenicol
Erythro/Clarithromycin
Sulfonamides (Trimethoprim)

Ciprofloxacin
Omeprazole
Metronidazole

Grapefruit
Alcohol
Verapamil
Itraconazole
Diltiazem

Question 13

CYP inhibitors

Answer 13

SCRAP GPS

St Johns Wort
Carbamazepine
Rifampicin
Alcohol
Phenytoin

Griseofulvin
Phenobarbital
Sulfonylureas

Question 14

CYP substrates

Answer 14

Warfarin
Statin
Contraceptives
TCAs

Question 15

P2 metabolism

Answer 15

Conjugation of drug with glucuronic / sulfuric acid to make more water soluble metabolites which are easily excreted

Question 16

Creatinine Clearance

Answer 16

CrCl = (140-age) x kg / SrCl x f

m = 1.23
f = 1.04

Question 17

Renal Disease

Answer 17

Stage 1 (normal) >90
Stage 2 60-89
Stage 3 30-59
Stage 4! 15-29
Stage 5 (failure) <15

CKD = <60 for >3m

Question 18

Half life ( t1/2)

Answer 18

time for concentration of drug in blood to reduce by half (<50%)

longer t1/2 = poor elimination

Question 19

Loading Dose

Answer 19

Ld = Vd x Cp / S x F

Cp (drug plasma conc / target)
S (salt factor - salt vs. non)
F = Bio.A

Question 20

Elimination rate

Answer 20

K = Cl / Vd

Question 21

First order

Question 22

Second order