Flashcards in Pharmacology Deck (98)
Define pharmacodynamics and pharmacokinetics
Pharmacodynamics - What a drug does to the body
Pharmacokinetics - what the body does to a drug - e.g absorption
What is the difference between an agonist and an antagonist?
An agonist binds to a receptor and produces a response.
An antagonist binds to a receptor, blocks another agonist and thus inhibits a response
Define affinity and efficacy
Affinity is the strength of association between the two substances
Efficacy is the ability to provoke a cellular response
N.B antagonists therefore possess affinity but LACK efficacy
On a graph showing the relationship between the concentration of an agonist and the response it produces, what is the EC50?
The EC50 is the concentration of agonists that elects a half maximal response
What is the difference between a competitive and a non-competitive antagonist?
Competitive - competes for the same active site (the same max response can be reached)
Non - competitive - binds to an alternative site, indirectly altering the shape of the active site
(the same max response can't be reached)
What is the relationship between lipid solubility and diffusion across the membrane?
The higher the lipid solubility of the drug, the more rapid the diffusion across the membrane.
What is pKA?
The pH at which 50% of a drug is ionised and 50% is unionised
What is meant by oral and systemic availability?
Oral Availability - The fraction of a drug that reaches the systemic circulation after oral ingestion
Systemic Availability - The fraction of a drug that reaches the systemic circulation after absorption
How does depolarisation and hyperpolaristation affect the membrane potential?
Depolarisation - causes the membrane potential to become less negative / more positive
Hyperpolarisation - cause the membrane potential to become more negative
What are the equilibrium potentials of sodium and potassium?
Sodium (Na+) = +60mv
Potassium (K+) = -90mv
What is meant by the absolute and relative refractory periods?
The absolute refractory period is when no stimulus however strong can elicit a second action potential
The relative refractory period is when a stronger than normal stimulus could cause another action potential
What is 'FIRST ORDER KINETICS' ?
The rate of elimination is directly proportional to the drug concentration
What does dosing to steady state mean?
The rate of drug administration equals the rate of drug elimination
What is half life?
The time taken for the amount of drug in the body to halve
What is 'ZERO ORDER?'
Elimination of the drug is not directly proportional to their concentration
Describe the process of how G-protein coupled receptors work
*Agonist binds and interacts with the G-protein
*GDP dissociates and GTP binds
*GTP is hydrolysed to GDP and Pi
The process by which a drug enters the tissues/ blood/ lymph
The movement of a drug from intercellular to intracellular by diffusion or membrane transport systems
The process by which tissue enzymes catalyse the chemical conversion of a drug to a less active but more polar form that is readily excreted from the body
The process that removes a drug or its metabolites from the body
Which accepts protons- Acid or base?
Do acidic drugs become more ionised in an acid environment?
No they become less ionised
Basic drugs become less ionised in a basic environment. True/ False?
What is the Henderson Hasselbach equation and what is it used to work out?
PKa-PH = Log (AH/A-) FOR AN ACID
PKa-PH = Log (BH+/B) FOR A BASE
*Used to work out the proportions of ionised and unionised drugs
The higher the pH , the more acidic drugs will be ionised and the less basic drugs will be ionised. True/ False
What is meant by free and bound drugs?
A free drug is simply dissolved in plasma
A bound drug is bound to a plasma protein
Vd < 10 implies what?
That a drug is largely retained in the vascular compartment (bound drugs/ drugs too large to cross capillary walls)
Vd 10-30 implies what?
A drug is largely restricted to extracellular water (drugs with low lipid solubility)
How many glycoprotein subunits do nicotine ACh receptors have?
5 glycoprotein subunits