Pharmacology Flashcards
(246 cards)
List the 3 types of drug interactions.
1) physicochemical
2) pharmacodynamic
3) pharmacokinetic
Define physicochemical drug interactions.
Drugs directly reacting with each other.
List 4 types of physicochemical drug interactions.
1) adsorption
2) precipitation
3) chelation
4) neutralisation
Give an example of a physicochemical drug interaction.
Paracetamol binding to activated charcoal (paracetamol overdose). Adsorption.
Define pharmacodynamic drug interactions.
Physical effect of a drug on the body.
what the drug does to the body
List 4 types of pharmacodynamic drug interactions.
1) summative reactions
2) synergistic reactions
3) antagonistic reactions
4) potentiation reactions
Define summative reactions.
1+1=2
Addition of 2 drugs works in the same way.
Give an example of a summative reaction.
sevoflurane + isoflurane
anaesthetics
Define synergistic reactions.
1+1>2
Addition of 2 drugs works better than they would individually.
Give 2 examples of a synergistic reaction.
1) paracetamol + morphine
2) paracetamol + ibuprofen
Define antagonistic reactions.
1+1=0
Drugs work against each other.
Give an example of antagonistic reactions.
morphine + naloxone
Define potentiation reactions.
1+1=1+1.5
Drug A increases drug B potency. Drug B doesn’t increase drug A potency.
Give an example of potentiation reactions.
probenicid + penicillin
Define pharmacokinetic drug interactions.
Movement of drug in the body.
What the body does with the drug.
List 4 factors that affect pharmacokinetic drug interactions.
1) absorption
2) distribution
3) metabolism
4) excretion
Define bioavailability.
Proportion of administered drug that is in systemic circulation.
What is bioavailability expressed as? (2)
1) percentage
2) fraction
What route of administration has a bioavailability of 100%/1?
Intravenous.
List 3 reasons why the bioavailability of oral drugs varies.
1) gut surface area
2) gut pH
3) diarrhoea
What oral drug has a very high bioavailability?
Paracetamol.
List 2 factors that affect absorption.
1) gut motility
2) gut acidity
What are 2 forms a drug exists as?
1) unionised - can pass through membrane
2) ionised - cannot pass through membrane
How does change in gut pH affect absorption?
Changes concentration of unionised and ionised forms of drug, therefore affects passage across membranes.