M104 T2 L14 Flashcards
What are the six rights of prescribing?
Right patient Right drug Right route Right dose Right time Right outcome
What is Pharmacokinetics about as a medical student?
it’s about relating its principles to clinical applications
What does having a knowledge of Pharmacodynamics help with?
the safe and effective use of medicines
working out the optimal dosage regimen
predicting potential drug interactions
How is the optimal dosage regimen worked out?
dose, route
dose interval
duration of treatment
What are the four subheadings of Pharmacokinetics? (ADME)
Absorption
Distribution
Metabolism
Excretion
Where does absorption of a drug take place normally?
a receptor site
What are the two types of routes for drug administration?
Enteral and Parenteral
What are the two routes of enteral drug administration?
Oral
Rectal
What are the two routes of parenteral drug administration?
Sublingual
Buccal
What happens to drugs administered buccally?
they are held or applied in the buccal area
they diffuse through the oral mucosa
they then enter directly into the bloodstream
What happens to drugs administered sublingually?
the drug is held under the tongue to dissolve
it is absorbed into the blood through the mucal membrane tissue there
What factors influence enteral absorption?
GI motility Absorptive area GI blood flow Drug properties Drug physicochemical properties Drug binding
How does rapid GI motility influence enteral absorption?
rapid GI motility means that there’s not enough time for the drug to maintain contact with the GI system
AAR it is not properly absorbed (fully)
How does inflammation influence enteral absorption?
it lowers the absorptive area available for the drug
How does GI blood flow influence enteral absorption?
lack of / suboptimal blood flow results in lowered absorption rates
What are two properties of drugs being absorbed?
particle size and formulation
How does drug binding influence enteral absorption?
the drug needs to be able to bind to cells in the GI system if it is going to be absorbed
What are examples of drug physicochemical properties that influence enteral absorption?
solubility
pH
How does solubility of drugs influence enteral absorption?
more lipid soluble, increased absorption
less more water soluble, decreased absorption
How does drug pH influence enteral absorption?
acidic drugs are better absorbed in acidic media
basic drugs are better absorbed in basic media
What types of molecules are not lipid soluble?
hydrophilic, polar or ionized mlcs, e.g. Na+, K+
What types of molecules are water soluble?
hydrophilic, polar or ionized mlcs, e.g. Na+, K+
Where are acidic drugs better absorbed?
in the stomach, e.g. aspirin
Where are basic drugs better absorbed?
in the intestines
Where are acidic drugs better absorbed?
in the acidic media
Where are acidic drugs better excreted?
in the basic media
Where are basic drugs better absorbed?
in the basic media
Where are basic drugs better excreted?
in acidic media
In what tissue layer are vaccines administered into?
vaccines
What are less common routes of drug administration?
Topical
Transdermal
Inhalational
Intrathecal
What are the more common tissue layers for drug administration?
subcutaneous
intradermal, intramuscular, intravenous
What are the less common tissue layers for drug administration?
Topical
Transdermal
Inhalational
Intrathecal
Between what levels is ideal dosing of a drug achieved?
below the MTC but above the MEC
Is 250mg of paracetamol four times a day optimal?
no because it is below the MEC so it’ll be ineffective
Is 3g of paracetamol four times a day optimal?
no because it is above the MTC so it could be dangerous
What are the pharmacokinetic concepts?
Absorption First-pass (pre-systemic metabolism) Bioavailability Bioequivalence Volume of distribution Cytochrome P450 enzyme system Half-life Steady state Clearance
What is the maximum dosage of paracetamol four times a day?
8x 500mg tablets a day
Will Crohn’s disease change the effectiveness of a contraceptive oral pill taken on a daily basis?
yes bc crohns can impair absorption
What is the equation for calculating Bioavailability?
oral AUC / IV AUC
What is the bioavailability of IV AUC?
100% bc all of it is directly entered into the bloodstream so all of it is absorbed
Which method has a higher bioavailability, oral or IV?
IV bc not no drug administered orally will make it into the blood 100%, while IV will
Which method has a higher bioavailability, oral or IV?
IV bc not no drug administered orally will make it into the blood 100%, while IV will
If a drug has an oral bioavailability of 20%, how will the oral dose be adjusted to achieve therapeutic effectiveness?
it will be ~5x higher than the corresponding IV dose
What is furosemide used to treat?
high bp, HF and oedema
Why does congestive heart failure decrease the bioavailability of an orally administered drug?
bc congestion in the heart also causes the organs to have oedemas, including in the gut
this increases the distance the drug has to travel through the gut to get into the bloodstream
What is the most suitable route of administration of drugs for stable HF?
orally
What is the most suitable route of administration of drugs for decompensated HF?
IV
What type of medication is furosemide?
a diuretic
What is the most appropriate route of administration of drugs for a patient with severe CAP and why?
IV bc bioavailiability is 100% and quick treatment is needed as they are very ill if it is SEVERE CAP
What is the most appropriate route of administration of drugs for a patient with CAP and why?
orally
What are examples of bacterial infections Amoxicillin is used to treat?
pneumonia, skin infections, and UTIs
How is Amoxicillin administered?
orally, less commonly by injection
Which pharmacokinetic parameter(s) is/are affected if a patient for osteoperosis takes alendronic acid at least 30 minutes before breakfast?
bioavailability and absorption
the bioavailability would already have been low (20-30%) but the food would reduce it further
What is the first pass metabolism otherwise known as?
pre-systemic metabolism
What is the effect of a high first pass effect on bioavailability?
it reduces BAVT
What is the effect of a low first pass effect on bioavailability?
it increases BAVT
Why is the sublingual route of drug administration suitable for a patient with stable angina?
bc it will bypass the GI tract and be administered directly to the blood stream instead
it will be exposed to extensive first pass metabolism
What type of medicine is glyceryl trinitrate?
a nitrate
What is GTN used to treat?
angina - can help stop chest pain if an angina attack has already started. It can also help to prevent them from starting
What can GTN ointment be used to treat?
tears in the skin around the bottom (anal fissures)
How can GTN be administered?
tablets, spray under tongue
patches and ointment on skin
When might GTN patches be used and for what purpose?
in hospital to make veins easier to see if administering a drip (infusion)
Why might it be a concern that a patient on propranolol for hyperthyroidism has deranged liver function?
?
What type of substance is propranolol?
a non-selective beta blocker
When are two drugs considered bioequivalent?
when there is no significant difference in the rate or extent of bioavailability at the same molar dose and under the same conditions
When might the bioequivalence of two drugs be relevant?
Different formulations from different companies
Different batches of drugs from the same company
