Principles Flashcards
(22 cards)
What is pharmacology?
study of drug action and its influence on physiological function
What is therapeutic effect?
effect prescribing a drug has on a patient
What are the drug targets?
receptors
enzymes
ion channels
transport proteins
How does selectivity of a drug affect its dosage?
dose of drug is administered is related to the selectivity of the drug
What are the drug receptor interactions?
electrostatic
hydrophobic
covalent - typically irreversible
stereospecific
What is the difference between antagonist, partial agonist and full agonit?
antagonist - block receptor by producing no response when they bind
partial agonist - affinity for receptor but sub maximal efficacy
full agonist - affinity for receptor and maximal efficacy
What is affinity?
strength of the drug receptor complex
What is efficacy?
ability of individual drug molecule to produce effect once bound to a receptor
What is potency?
refers to conc or dose of drug needed to produce defined effect, standard measure is EC50 or ED50
What are the major pharmacokinetic factors?
absorption - passage of drug from site of administration to plasma
distribution
metabolism
excretion
What is bioavailability?
fraction of the initial dose that gains access to systemic circulation
Where is a weak base drug least likely to be absorbed?
in the stomach because of low pH
Where are weak acids least likely to be absorbed?
from the blood
What carrier systems are most important?
those in the renal tubule
biliary tract
blood brain barrier
How do drugs move around the body?
through bulk flow transfer - in the blood stream or
diffusional transfer across short distances
How do drugs diffuse?
through simple diffusion
diffusion across aqueous pores
carrier mediated transport
electrochemical gradient
What factors affect distribution?
regional blood flow - diff organs receive diff cardiac output
plasma protein binding - albumin binds acidic drugs, determines on bioavailability of the drug
capillary permeability - lipid soluble drugs can diffuse, others cant
tissue localisation - lipid solube and water soluble localise at different places due to equilibrium
What is a major metabolic tissue?
liver - has cytochrome p450 enzymes for drug metabolism
What are the phases of drug metabolism?
phase 1 - introduce reactive groups to drug
phase 2 - add conjugate to reactive groups
How do we deal with drugs that are passed through hepatic metabolism?
because the drug is heavily metabolised in the livr, little will reach the systemic circulation. administer a higher dose to ensure enough reaches systemic circulation
How are drugs excreted in the kidney?
glomerular filtration
active tubular secretion
passive diffusion across the tubular epithelium
What is biliary excretion most commonly used for?
2 glucuronide metabolites however enterohepatic recycling can occur which can prolong the drug effect
