Lecture 3 - Pharmaocdynamics And Pharmacokinetics Flashcards
(102 cards)
What are the 4 main processes in drug administration?
Absorption
Distribution
Metabolism
Excretion
What form of a drug is functional?
When it is the free drug and not bound to transporters
What are the regulatory bodies interested in the Pharmacokinetics of a drug that are responsible for approval and standardisation of dosing?
MHRA
EMA
FDA
What are some key factors that must be considered when assessing pharmacokinetics?
Bio-availability
Half-life
Drug eliminate
Inter patient variability
Drug-drug interactions
What bodily functions should we consider when thinking about pharmacokinetics?
Renal function
Stress
Pyrexia
Liver function
Gi function
CVS function
Immune status
What is bioavailability?
The measure of drug absorption where it can be used
How much of a drug can be measured of a drug in the plasma when its given via IV or oral
What method of drug administration gives 100% bioavailability?
IV (intravenous)
How would you calculate bioavailability of a drug given via oral?
Fraction of what the IV would be
AUC oral/AUC IV x 100
What affects bioavailability?
Absorption ability (formulation, age, food, vomiting, previous surgery)
First Pass metabolism
What is first pass metabolism?
When drugs are metabolised before they reach the systemic circulation (gut lumen, ,gut wall, liver and even lungs)
What drug uis given to help relieve an angina attack via being absorbed by tongue mucosa?
GTN spray
How does GTN spray work?
Smooth muscle vasodilation helping widen blood vessels supplying the heart
Why is metformin a modified released preparation?
Side effect of metformin is GI upset, so by making it so you have to take it less frequently reduces the frequency of GI upset
What is a modified released preparation?
When the drug is modified to be released at a specific rate so that large fluctuations inn plasma concentration dont happen so have to take drug less frequently
Why shouldn’t modified release tablets be crushed before taking?
Negates the affect of the modification that controls the rate of release of the drug
How does metformin work?
Decrease the livers synthesis of glucose helping to treat diabetes Mellitus (Gluconeogenesis)
Also makes body more sensitve to insulin
What are some factors that affect the ability of a drug to be distributed through the body?
Blood flow/capillary structure (how well perfused the tissue is)
Lipophilicity and hypophilicity
Protein binding
What are some common proteins that bind to drugs?
Albumin (acidic drugs)
Globulins (hormones)
Lipoproteins (basic drugs)
Glycoproteins (basic drugs)
What stops the majority of drugs from affecting the brain?
What cells contribute to this?
Blood Brain Barrier
Foot processes of Astrocytes
What is the volume of distribution of a drug?
The volume of distribution (Vd) is a pharmacokinetic parameter representing an individual drug’s propensity to either remain in the plasma or redistribute to other tissue compartments
What is negative about a narrow therapeutic index?
A small change in concentration of the drug can have toxic affects if too high or very little affect if too low
What is important to consider when prescribing multiple drugs?
One may have a higher protein binding affinty that the other. So when the other drug is administered it may displace the first drug from the protiens leading to more free circulating drug than anaticapted leading to toxic affects
What is apparent volume of distribution>
The amount of a drug given whose concentration can be measured in the plasma
What would the apparent voliuiume of distribution of a drug that’s given as a 100mg dose but its measured as a plasma concentration as 20mg/L?
100mg/20mg/? = 5
Vd = 5L
