Drug Therapy

Question 1

Physico-chemical factors that affect the transfer of drugs across cell membranes

Answer 1

Ionisation - changes in pH
Lipid solubility - must be lipid soluble in order to diffuse across phospholipid bilayer
Structure - Must resemble naturally occurring substances to be able to fit through the pumps

Question 2

Factors affecting absorption of a drug from the GI tract

Answer 2

Motility (speed of gastric activity)
Food (impairs or enhances absorption)
Illness (malabsorption, migraines reduce rate of stomach emptying

Question 3

First pass metabolism

Answer 3

Metabolism of the drug prior to it reaching the site of absorption

Question 4

Benefits of IV medication

Answer 4

Avoids first pass metabolism

100% bioavailability

Question 5

Benefits of topical medication

Answer 5

Can achieve local or systemic effects
Able to achieve controlled, sustained doses of the drug
Avoids first pass metabolism

Question 6

Benefits of inhaled medication

Answer 6

Drug delivered directly to site of action
Rapid effect
Small doses used
Little systemic absorption
Reduced adverse effects

Question 7

Bioavailability

Answer 7

Amount of drug that reaches circulation and is available for action

Question 8

Factors that determine bioavailability

Answer 8

Formulation
Ability to pass physiological barriers
GI effects
First pass metabolism
Particle size
pH and ionisation 
Food
Illness

Question 9

Preparation forms of oral administration

Answer 9

Solutions
Suspensions
Tablets and capsules
Enteric coated tablets

Question 10

Phase 1 drug metabolism

Answer 10

Involves oxidation, reduction or hydrolysis
Increases polarity
Provides active site for phase 2
Mainly carried out by P-450 family of enzymes

Question 11

Phase 2 metabolism

Answer 11

Involves conjugation
Increases water solubility of compound, makes excretion easier
Most drugs inactivated by conjugation but some may remain active

Question 12

Factors that inhibit or induce drug metabolism

Answer 12

Other drugs/substances
Genetics
Hepatic blood flow
Liver disease
Age
Sex
Ethnicity

Question 13

Factors that determine drug metabolism

Answer 13

MUST LEAVE CIRCULATION AND ENTER TISSUES
Plasma protein binding
Tissue perfusion
Membrane characteristics
Blood-brain barrier
Transport mechanisms
Diseases/other drugs

Question 14

Renal drug excretion

Answer 14

Glomerular filtration
Active tubular secretion
Passive tubular reabsorption

Question 15

Glomerular filtration

Answer 15

All unbound drugs are filtered at the glomerulus as long as their size or charge does not prevent this

Question 16

Active tubular secretion

Answer 16

Some drugs are actively secreted into the proximal tubules of the kidneys
Main method of excretion for protein bound cationic and an ionic drugs

Question 17

Passive tubular reabsorption

Answer 17

As filtrate moves down kidney tubules, becomes more positive => body reabsorbs some of the drug (only unionised drug though)
Also affected by renal failure

Question 18

Factors that predispose a patient to drug interactions

Answer 18

Patient specific - advanced age (young/old), genetic polymorphisms, concomitant diseases

Drug specific - polypharmacy, narrow therapeutic range, dose

Question 19

Classification of drug-drug interactions

Answer 19

Direct
Indirect
Antagonistic
Synergistic/agonistic

Question 20

Types of adverse drug reaction

Answer 20

Augmented
Bizarre
Chronic
Delayed
End of treatment
Failure of treatment

Question 21

Augmented (ADR)

Answer 21

Predictable
Dose dependent
Resolved when drug is stopped
Recognised before drug is available

Question 22

Bizarre (ADR)

Answer 22

Unpredictable
Rare
Serious illness/death
Unrelated to dose

Question 23

Chronic (ADR)

Answer 23

Related to dose
Related to length of treatment
Semi-predictable

Question 24

Delayed (ADR)

Answer 24

Occurs years after treatment, or in children of patient

Question 25

End of treatment (ADR)

Answer 25

Effects caused when drug is stopped, especially suddenly

Question 26

Failure of treatment (ADR)

Answer 26

Common

Frequently caused by drug interactions