Basic Pharmacology Flashcards
(31 cards)
What is the meaning of “Pharmacology”?
Study of how a drug affects the biological system & how the body responds to the drug
What is the meaning of “Pharmacodynamics”?
Study of what the drug does to the body
What is the meaning of “Pharmacokinetics”?
Study of what the body does to the drug
What is the meaning of “Pharmacogenomics”?
Study of the role of genomes in drug response
What are the principles of pharmacodynamics?
Downstream signaling - process where a signal is transmitted by a receptor / effector molecule to activate intracellular signalling events; lead to changes in
- gene expression
-protein activity
- cellular behaviour
What are the concepts of receptors?
- Responsible for the selectivity of drug actions
- Determine the quantitative relations concentration of drugs & it’s effects (high receptor affinity = lower concentration of drug dose required to Brin about action)
- Mediate the action of Pharma-antagonists
What are the different drug types leading to different effects?
- Agonist - regulate the function of receptors & activates it
- Antagonist (competitive) - share the same receptor site as endogenous molecule; block agonist from binding to receptors
- Allosteric activator - increase affinity of receptors leading to enhanced activity
- Antagonist (non-competitive) - bind to different receptor site from agonist leading to inhibition of activity
What are the different ways to classify drugs?
- Indication - what is the drug used for
- Chemical structures - agonist. antagonist, etc)
- Mechanism of actions (what is it’s effect)
What is the clinical use of Clopidogrel?
Action - platelet inhibitor; used to reduce the risk of MI infection / stroke
- irreversibly inhibits P2Y12 which is a subtype of ADP receptor
- P2Y12 is required for platelet activation & cross-linking of fibrin
What is the side effects of using Clopidogrel?
- excessive bleeding
- secondary to inhibitory effect on platelet function
What are the 4 principles of pharmacokinetic principles?
Absorption, Distribution, Metabolim, Excretion
What is the definition of Bioavailability?
The amount to unchanged drug that reached the systemic circulation after administration; the extent of drug absorption
- BA differs with the route of administration
- IV BA 100%
What are the main modes of absorption?
- Passive diffusion
- Facilitated passive diffusion
- Active diffusion
What is the first pass effect?
Drugs that is metabolised at a specific location in the body (mostly liver), resulting in a reduced concentration of the active drug upon reaching it’s site of action / systemic circulation
What are the factors affecting drug absorption?
Drug factors
- Degree of ionization
- Lipid solubility
- Molecule size
- pKa (higher pKa = lower pH)
- Stability in gastric acid
Patient factors
- Area of absorptive surface
- Gut pH
- Gut motility
- Presence of food or other drugs
What is Volume of distribution (Vd)?
The amount of drug in the body in relation to the concentration in the plasma / blood
- High Vd = drug going into tissues & organs; little stay in blood
- Low Vd = drug staying in blood; does not go to organs / tissues
How does protein affect drug distribution?
Drugs can bind to proteins
- Higher % of drug binding to proteins = smaller Vd
What are the factors affecting drug distribution?
Drug factors
- Degree of ionization
- Lipid solubility
- Molecule size
- Protein binding
- Partition coefficient
Patient factors
- Fat & water content
- Protein level
- Disease status
- Concomitant drugs
What is the meaning of Biotransformation?
It refers to the metabolisation of drugs into a more hydrophilic form for it to be cleared by the kidneys
- Most metabolism occurs in the liver
What are the 2 main enzymatic phases?
Phase 1 - reaction of functionalization
- creating a functional group / modification of existing group (i.e. oxidation, reduction, hydrolysis)
- typically involves CYP450 enzymes (heme-containing)
- CYP3A4 is the most prevalent
- CYP enzymes helps to breakdown non-drug compounds (alcohol by CYP2E1)
Phase 2 - reaction of conjugation
- coupling a drug with endogenous molecule to make it more hydrophilic
- Eg. of molecules - glucuronidation, Sulphation, acetylation
What are the factors affecting drug metabolism?
Drug delivery factors
- blood flow to liver
- protein binding
Intrinsics factors
- metabolising capacity depending on genetics
- concomitant interacting drugs
- genetic polymorphism - presence of 2 or > variants of a specific DNA
How does drug-drug interaction occur during Phase 1 of biotransformation?
Via inhibition / induction of CYP enzymes
Eg. Warfarin + CYP = increase effect of warfarin = increased anticoagulant effect
How are drugs excreted?
Metabolites & parent drugs are eliminated from the kidneys and excreted in the urine
- Accumulation of drugs may occur in patients with kidney dysfunction
- Might need to alter the type of drug / reduce the dosing
What is the definition of half-life?
The time taken for the concentration of drugs to reduce to half; how fast the drugs can be cleared from the body
- Shorter T1/2 = faster drug clearance = more frequent dosing
- Dosing of drugs depends of T1/2
