Pharmacodynamics Flashcards
What are the different types of adverse effects?
-Quantitative- expected, unwanted consequences of the drug or toxicity due to high doses (eg hypertension if too much metaraminol)
-Qualitative effects ie unwanted effects due to hypersensitivity or idiosyncrasy
WHat is tolerance?
Decreased effect following repeated exposure to a drug
What is tachyphylaxis?
Decreased responsiveness after a single dose of a drug
What is sensitisation?
Increased response after repeated exposure to a drug
What is a class 1 receptro and example
ligand gated ion channel eg nACH receptor
WHat is class 2 receptor and example
GPCR (metabotropic)
eg mACh receptor
t3 receptor and example
kinase linked receptor-cytokine receptors
T4 receptor and example
Nuclear receptor
Oestrogen receptor
DIfferent types of G protein?
Gi, Gs, Gq
WHat does an activated Gs do?
Increase cAMP
What does activated Gi do?
decrease cAMP
What does activated Gq do
increase DAG or IP3
How does an activated alpha unit of a g protein return to resting state
Phosphorylase on the alpha subunit cleaves a phosphate from GTP to form GDP/the inactivated form of the subunit. This can then recombine with the BY subunit
What is ED50
immediate effective dose 50%
Dose of drug that produces a specified response in 50% of the population to which it was administered
What is EC50
Median effective concentration 50%
Concentration that induces a response halfway between 0 and max
What is the therapeutic window?
Difference between the dose that produces desired effects and the dose that produces undesired effects
How do we calculate the therapeutic index
LD50/ED50
(lethal dose in 50%)
Examples of drugs with narrow therapeutic windows/low therapeutic index
Warfarin, aminoglycosides, theophylline, phenytoin
What is affinity
Strength of association btw drug + receptor
WHat is Kd
DIssociation constant
Drug dose at which 50 % of receptors are bound + 50% unbound
What is efficacy
The ability of a drug to interact with a receptor and produce a response
What is potency
The ability of a drug to produce a certain effect at a certain dose. Determined by pharmacokinetics
TYpes of antagonist?
Competitive
Non competitive
Irreversible
Partial agonists and affinity?
GEnerally lower than full agonists, though they can be the same
Hepatic enzyme inducers?
Phenytoin
CIgarette smoking
Rifampicin
CHronic alcohol
Enflurane
Halothane
Phenobarbitol
Thiopental
Phenytoin
Carbamazepine
Steroids
Hepatic enzyme inhibitors
MEtronidzaole
Isoniazid
Chloramphenicol
Phenelzine
Trancypromine
Cimetidine
Grapefruit juice
Amiodarone
Drugs affected by acetylator status?
Hydralazine
Isoniazid
sulphonamides
phenelzine
dapsone
procainamide
Rapid acetylator status inheritance?
AD- 40% o f pop
Slow acetylator status inheritence
AR
WHat are the different types of drug anatagonism?
Competitive
Non competitive
Physiological
Chemical
WHat is competitive drug antagonism
Drugs bind reversibly and the interaction can be overcome by increasing the concentration of the agonist
What is non competitive drug antagonism?
Irreversible binding of drugs (usually covalent) that cannot be overcome
WHat is physiological antagonism od drugs?
WHere the opposing actions cancel each other out- eg norad increasing BP histamine decreasing BP
WHat is chemical antagonism of drugs
Direct interaction which removes the drug or prevents it reaching the target ( eg penicillamine chelating lead)
Examples of drugs acting to inhibit enzymes?
Allopurinol (xanthine oxidase)
Physostigmine (anticholinesterase)
Indomethacin (cyclooxygenase)
Enoxomone (phosphodiesteradse)
Drugs that exhibit tachyphlyaxis?
GTN
Ephedrine
Trimetaphan
Example of a mixed agonist-antagonist?
Opioids (Pentazocine, Nalbuphine and Buprenorphine), Mirtazepine, Pindolol and Xameterol
