Med Chem 1 Flashcards
What is the blood brain barrier
Prevents drugs accessing the brain as cells are tightly joined
Where are oral drugs absorbed?
In the small intestine.
Affected by:
physicochemical properties of drug
contents of the gut
lipid solubility
formulation
What is Therapeutic Index
Ratio between toxic dose / effective dose in blood plasma
Low therapeutic index = small distance between therapeutic dose and harmful dose.
Digoxin has a TI of 2:1, paracetamol has a TI of around 7:1, Lithium, Warfarin, insulin around 2:1
What are the advantages and disadvantages of skin route of administration?
Advantages
Local or systemic action
Avoid FPM & GI tract
Disadvantages
Irritation, absorption varies
What are the advantages and disadvantages of nasal route of administration?
Advantages
Local or systemic action
Avoid FPM & GI tract
Disadvantages
Irritation, absorption varies
What are the advantages and disadvantages of oral route of administration?
Advantages
Patient compliance & Self admin
Good product stability, Controlled release
Disadvantages
Slow onset, Variable BioA, FPM, stability in GI tract. Effect of food
Patient must be awake
What are the advantages and disadvantages of buccal / sublingual routes of administration?
Advantages
Local or systemic action
Avoid FPM & GI tract
Rapid onset
Disadvantages
Taste, low dose, must be retained in mouth
What are the advantages and disadvantages of subcutaneous route of administration?
Advantages
Avoid FPM & GI tract
Prolonged delivery & self admin possible
Disadvantages
Painful, irreversible dosing, irritation/ tolerance. sterile product (infect), variable stability
What are the advantages and disadvantages of lung route of administration?
Advantages
Avoid FPM & GI tract
Local and rapid action
Disadvantages
Majority dose swallowed, patient coordination, irritation to lung, propellant toxicity
What are the advantages and disadvantages of intravenous route of administration?
Advantages
Avoid FPM & GI tract
Immediate & 100% Bio A
Unconscious patient
Disadvantages
Trained personnel gives dose,
Painful, irreversible dosing, irritation/ tolerance. sterile product (infect), variable stability
What are the advantages and disadvantages of vaginal route of administration?
Advantages
Avoid FPM
Local or systemic action
Disadvantages
Inconvenient, absorption varies, irritation
What are the advantages and disadvantages of ears route of administration?
Advantages
Local effect
Disadvantages
May be difficult to self-administer (drops)
Slow (keep head tilted)
What are the advantages and disadvantages of rectal route of administration?
Advantages
Local or systemic action
Avoid FPM & GI tract
Disadvantages
Unpopular, inconvenient, absorption slow/varies, irritation
What are the advantages and disadvantages of eyes route of administration?
Advantages
Location action only
Disadvantages
Large dose lost, sterile (infection).
What are the advantages and disadvantages of intramuscular route of administration?
Advantages
Avoid FPM & GI tract
Prolonged delivery & self admin possible
Disadvantages
Painful, irreversible dosing, irritation/ tolerance. sterile product (infect), variable stability
What sorts of injection are there and why would you use them?
IV – into vein (electrolytes, anaesthetics, pain relief, nutrition)
IM – intramuscular – relatively quick, good blood supply. (vaccines, hormones)
SC – subcutaneous – insulin, heparin
IO – intraosseous – into the bone marrow – generally emergency when veins not working
ID – intradermal – tuberculosis vaccine
What is pharmacokinetics and what is pharmacodynamics
Pharmacokinetics is how a drug moves through the body whereas pharmacodynamics is how the drug affects the body
What is A of ADME and how does it work?
Absorption - drug moves from site of administration across one or more membranes into the bloodstream and cells.
Passive transport moves through cell on its own. Active transport requires ATP to move through the cell wall
What is D of ADME and how does it work?
Distribution - the drug journey around the body to reach the target cells and molecules.
If drug binds too tightly to plasma proteins then cannot reach the target.
Can be hindered by membranes such as blood-brain barrier, blood-placenta barrier
What is M of ADME and how does it work?
Metabolism - the action by enzymes to render the drug ineffective.
Usually trying to make more ionic so dissolves
What is E of ADME and how does it work?
Excretion - removal from the body.
Kidneys involved here as metabolites passed through to urine.
Some drugs excreted into bile that then excreted into GI tract
How are oral drugs metablolised?
Metabolism of oral drugs - through the small intestine to the liver via the hepatic portal. Takes drug to the liver where it gets metabolised. This is the 1st Pass mechanism and reduces the bioavailability.
Drugs also metabolised in the blood by enzymes (body protects against small molecule with enzymes and large molecule pathogens with the immune system)
What is a Pro-drug
If metabolism activates the drug then it is a Pro-drug (codeine metabolised to morphine).
Salts may aid bioavailability but are not pro-drugs as don’t need metabolic activity to realise their therapeutic effect.
What are agonist and antagonists?
Any receptor has a ligand that activates it.
Agonist - fits onto the receptor and mimics the ligand to activate the signal (facilitator)
Antagonist - fits onto the receptor and blanks it off to prevent the signal (inhibitor / blocker)
