Flashcards in Pharmacology Deck (246)
List the 3 types of drug interactions.
Define physicochemical drug interactions.
Drugs directly reacting with each other.
List 4 types of physicochemical drug interactions.
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.
Addition of 2 drugs works in the same way.
Give an example of a summative reaction.
sevoflurane + isoflurane
Define synergistic reactions.
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.
Drugs work against each other.
Give an example of antagonistic reactions.
morphine + naloxone
Define potentiation reactions.
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.
Proportion of administered drug that is in systemic circulation.
What is bioavailability expressed as? (2)
What route of administration has a bioavailability of 100%/1?
List 3 reasons why the bioavailability of oral drugs varies.
1) gut surface area
2) gut pH
What oral drug has a very high bioavailability?
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.
List 3 ‘places’ a drug could be distributed from a blood vessel.
1) bind to plasma protein
2) effect site
3) other tissue
What is the effect of a drug binding to a plasma protein.
It exerts no clinical effect.
What organ is most important for drug metabolism?
Describe alcohol and the metabolism of morphine. (5)
1) morphine is metabolised by cytochrome P450 enzymes in the liver into morphine-6-glucoronide
2) morphine-6-glucoronide is 10x more effective than morphine
3) alcohol increases efficacy of cytochrome P450 enzymes
4) concentration of morphine-6-glucoronide increases due to alcohol
5) analgesic effect increases due to alcohol
What is altered to improve excretion of a drug?