240918 Basic pharmacology Flashcards
Define pharmacodynamics
The effect that a drug has on the body
Name four agents that help mediate the effect a drug has on the body
Receptors on the cell surface
Carrier molecules
Enzymes
Specific macromolecules (e.g. DNA)
What are receptors and how are they activated?
Receptors are usually a protein molecule found on the surface of the cell or in the cytoplasm
They are activated when a drug binds to it to form a drug-receptor complex.
What’s the difference between an agonist and an antagonist? And name the two different types of antagonists
Agonist = Drug that has affinity for a receptor and once bound causes a specific response
Antagonist = Drugs that bind to a receptor to block a response. Most bind with them but do not activate (i) Competitive – e.g. naloxone
(ii) Non-competitive e.g. nifedipine
What is a partial agonist/antagonist?
A drug that acts on receptor sites and elicits a smaller pharmacological response compared with a complete agonist / antagonist
Define specificity and affinity
Specificity = How good a drug is at binding with a receptor. (No single drug is totally specific to one receptor therefore we get side effects)
Affinity = The strength of the interaction between a drug & a binding site of the receptor
The closer the fit the greater attraction & greater affinity
Define pharmacokinetics and list the 4 processes that underpin it
The branch of pharmacology concerned with the movement of drugs within the body
Absorption - getting the drug into systemic circulation, i.e. administration (e.g. intravenous, oral, rectal, inhalation etc.)
Distribution - getting it to the various tissues
Metabolism - breaking it down
Excretion - removing it from the body
What is first pass metabolism?
Drugs absorbed from the GI tract enter the portal circulation and some are extensively metabolised as they pass through the liver
Define bioavailability and name the administration method that results in 100% bioavailability
The term to describe the proportion of the drug that reaches the systemic circulation
Bioavailability is 100% with IV injections
Define tolerance
reduced reaction to a drug following its repeated use
List 6 factors that affect the distribution of a drug
Blood flow – e.g. heart faster than bone
Plasma protein binding - amount of dug not bound to a protein (usually albumin) that is available to produce an effect.
Displacement - of one bound drug by another e.g. warfarin can be displaced by tolbutamide
Placental barrier
Blood brain barrier
Storage sites - do drugs accumulate in the fat for example?
Define ‘volume of distribution’, explain why distribution may be uneven, and distinguish between high and low volume of distribution
The estimated amount of dug left in the bloodstream after absorption & distribution is complete.
Drugs are distributed unevenly between various body fluids & tissue fluids due to their physical & chemical composition
A low volume of distribution means mainly confined to blood & body water e.g. gentamicin
A high volume of distribution means the drug has overflowed into the tissues e.g. digoxin, propranolol
Define metabolism, state where it mainly occurs, and name four processes through which it occurs
Drug metabolismis the chemical alteration of adrugby thebody.
oxidation, reduction, hydrolysis & conjugation
List 6 factors affecting metabolism
Genetic factors e.g. genetic inheritance to atypical form of pseudocholinesterase causing prolonged paralysis with suxamethonium
Age - older people first pass metabolism may be reduced or delayed. Neonates – enzyme responsible for conjugation may be underdeveloped
Disease process – e.g. liver disease – reduced hepatic blood flow/ accumulation
Ethnicity
Drug interactions
Tobacco smoke e.g. Clozapine
List 9 routes of drug excretion
Hair
Saliva
Milk
Sweat
Alveolar (breath)
Bilary (in the bile)
Renal (urine)
Faecal
