DONE Pharmacokinetics

Question 1

Focal administration of drugs

Answer 1

Eyes/skin/inhalation = less systemic absorption (fewer side effects), concentrates drug @ site of action

Question 2

Drug absorption

Answer 2

Little absorption in stomach (small SA)

Constant movement in small intestine = more uptake

Question 3

Drug absorption passive diffusion

Answer 3

Weak acids/bases
Diffuse if uncharged
Lipophilic drugs

Question 4

Drug absorption facilitated diffusion

Answer 4

E.g. glucose (if a drug is charged)
Solute carrier transport (SLC)
Charge within GI pH range = cross GI epithelia
Driven by electrochemical gradient on solute
SLCs = organic anion transporters (OATs) or organic cation transporters (OCTs)

Question 5

Factors affecting drug absorption

Answer 5

GI surface/length
Drug lipophilicity 
Blood flow (increased post meal)
GI motility (slow post meal)
Low pH destroy drugs

Question 6

First pass metabolism

Answer 6

GI and liver = gut/bacteria enzymes denature some drugs =
CYP450s (phase 1 enzymes) + conjugating enzymes (phase 2)
Reduces drug availability to systemic circulation

Question 7

How to avoid first pass metabolism

Answer 7

Parenteral or rectal (but drains to portal + systemic systems) or sublingual

Question 8

Class 1 drugs/object drug

Answer 8

Dose less than available binding sites = conc of free drug low

E.g. warfarin

Question 9

Class 2 drugs/precipitant drug

Answer 9

Dose greater than available binding sites, displaces class 1 drug

E.g. aspirin

Question 10

What is pharmacokinetics?

Answer 10

What body does to drug (ADME) or is it getting to site of action

Question 11

What are the main factors affecting rates of drugs in/out of the body?

Answer 11

ADME

Absorption (drug in)
Distribution (drug in)

Metabolism (out)
Elimination (out)

Question 12

What are the factors affecting drug distribution?

Answer 12

Drug lipophilicity or hydrophilicity
Degree of drug binding to plasma/tissue proteins (decrease free drug available, acts as reservoir, e.g. albumin/lipoproteins, only FREE DRUG MOLECULES can bind to target + have therapeutic effect)

Question 13

What can affect Vd?

Answer 13

Drugs with narrow therapeutic ratio
Pregnancy
Marked changes in body weight