Pharamacology Lecture Flashcards
Define a drug
Chemical ages capable of producing a biological effect that be desirable or undesirable
What’s a biologic
Agents naturally prouduced in cells
How do you name a drug
Chemical name = structural formula of chemical
Generic name = used by the wider population eg. Aspirin
Proprietary name = manufacture specific name
Outline the general flow of drug movement through the body (pharmacokinetics)
Absorption
Distribution
Biotransformation/metabolism
Elimination
Explain the factors that go into the decision of absorption of the drug
Can be administered directly into blood via IV or get the drug through body and into blood
We have routes we can use for administration which is dependent on:
- formulation of drug
- patient comfort (tablet the most easy so pt will go for this)
- ease of administration
- plasma levels required
Exaplin drug admintration in terms of IV injection
IV
- rapid effect (absorption isn’t required)
- used as slow continuous infusion
- increased risk of toxicity
- main route for contrast media
- important route for emergency medicine
- only some drugs suitable (ie. not suspension (drug particles is suspended in and will sediments in the bottom when at rest - you can kill the patient if a suspension is injected IV)
solution (drug is dissolved in fluid completely)
Explain drug administration in terms of oral
Convenient
Slow absorption
Used with instruction (fasted or with food (acidic environment activation))
Many drugs would be unsuitable for liver metabolism ie. morphine (so we do IV)
Used for barium
Explain drug administration in terms of sublingual
Under the tongue ie. drugs treated to use angina
Convenient
Rapid absorption
Explain drug administration in terms of nebulisation
Rapid absorption
Drugs is converted into a fuse (mist - droplets of fluid) which can be inhaled
- can be admintrated directly into the region without spread to other parts ie. lungs
Explain drug administration in terms of intramuscular injection
Useful for depot effect
Prolonged drug affect
Depot effect = slowly absorbed during a period of time
Place under muscle through injection (can cause pain)
Explain how the drug is actually distributed in the body
Many drugs are transported when bound to plasma proteins (especially lipid soluble drugs as they can’t dissolve in plasma)
Only the free form of the drug can have a biological effect (this is what’s used in dose calculation)
Eg. Warfarin = 99% plasma protein (albumin) bound, thus only 1% of the dose has a biological effect and the remainder is a depot
Some NSAIDs have greater protein affinity than warfarin and will displace it and lead to toxic effects. It will basically make you overdose as there’s an increase in free warfarin to effect you biologically
Liver or renal disease pt = low protein levels in blood causing to toxicity
Explain what’s the first pass effect
It’s relevant to drug distribution that occurs when you admin orally
So orally administrated drugs = pass through liver after absorption before reaching parts of body
Many drugs are extensively metabolised (where they broken down extremely) before even getting to the region of interest
Exaplin whats biotransformation/metabolism
Drugs that have low water solubility are metabolised in liver to make them more soluble
However, the metabolic conversion of drugs may decrease its pharmacological activity, but other times metabolism of the drug may be required to activate it
Biotransformation is affected by
- age (lowered as you age)
- sex
- genetics
- health
- concurrent and previous intake of drugs (increase capacity to breakdown the drug)p, less enxymes to accomodate, more drugs you to take the greater the amount of enzymes you’ll have
Explain what’s elimination
Can occur usually most common via kidneys
- as you get older kidney function decreases (elimination slows down)
Usually urine but the ph of urine can affect rate of excretion
What’s efficacy of a drug
How well a medication produces its desired effect
Used to measure drug action
What’s potency of a drug
Amount of medication required to produce a desired effect and thus is related very closely to dose
Used to measure drug action
What’s half life
It’s the interval required for the elimination processes to reduce drug concentration in body to 50%
This is the most common method of measure drug action
As you get older you excretion rate decreases, hence half life increases
When measuring drug action, what do we have to consider for it to be deemed effective
The drugs concentrations must
- exceed the minimum effective concentration (MEC)
- remain below minimum toxic concentration (MTX)
the safety margin between the MEC and MTC is the THERAPUTIC INDEX. So we basically dose the patient in terms of the half life of the drug through time. So in that sense, as you age, half life of drugs increase and so there’s more chances for toxicity to occur as you get a build up of drug doses that go beyond the therapeutic index.
Small gap makes it really hard, you have to dose that pt. Many time over time interval, and big gap allows were less frequent doses
How do drugs exert their effect
Their effect takes place intracellularly
The drug combines to a receptor (intracellular or extracellular)
Extracellular receptors = non-lipid soluble (water soluble)
Intracellular receptors = lipid soluble drugs
Some Drugs usually serve as a agonist, in which they mimic the function/structure of other physiological substances
Some drugs usually serve as a antagonist, in which they combine with receptor and prevent physiological substances from having a effect
Give examples of an agonist and antagonist
They both possess specificity to the receptors
Agonist = ventolin (bronchodilators) that bind to the adrenaline receptors of the airway cells and dilate the bronchioles ie. asthma patients with narrow airways
Antagonist = beta blockers used to block of adrenaline receptors to combat hypertension (high blood pressure) as adrenaline isn’t being activated
Explain the relationship of dose on effect
As you increase drug dose, more receptors will be activated therefore the effect will be greater
Drugs can work synergystically to increase their effect rather than just working by themselves
What type of adverse reactions can occur when administering a drug dose?
Non immunological
Immunological
Explain what’re non immunological adverse reactions to drugs
Toxicity
- predictable dose related reaction
Idiosyncratic reaction
- unexpected response to administration (that be excessive response or failure to respond)
- interaction with other drugs
- pre existing condition becomes severe
Explain what’re immunological adverse reactions to drugs
Allergy
- unpredictable reaction (toxicity is predictable) even at low exposures (can occur anytime even if you’ve used the drug before, an allergic reaction can occur)
- not an effect of drug itself rather body chemistry (immune response). Therefore these immune responses must be sesnsetised
- can be a rash or even an anaphylaxis (severe)
After one allergic reaction, it will then occur from there on out
Ie. allergic reaction to contrast media are common
How can an adverse reaction to a drug be detected?
There should be a temporal relationship between dosage and reaction,
Time and dose
Give a pt. A drug at time 0 and 20 mins later, there’s indication with the patient getting rashes or something
So if you withdraw the drug, the reaction will cease and then it will resume when drug is reintroduced
Explain the difference Between dependence and tolerance
Dependance = developing a physical need for drug and is unable to function normally without it ADDICTION
Tolerance = increasing dose required to achieve the same effect
What types of contrast media are there
Iconic contrast media
Non ionic contrast media
Barium sulphate
Contrast agents for MRI
These are all usually administered IV or intra arterial
What’s ionic contrast media
Carried freely in plasma (since they are ionic and so are soluble in plasma) where less than 5% of dose is protein bound
Immediately after injection the agent begins to diffuse into extravascular space, and water is drawn from the intravascular compartment
5 mins in = conc of intravascular and extravascualr compartments is same in most tissues (except neural)
Excreted via kidneys (renal disease = liver is alternative pathway)
No significant metabolism occurs
Who are at high risk to develop adverse reactions to ionic contrast media
- who’ve had previous reactions to media
- asthma or significant allergic disease
- anaphylactic history
- cardiovascular disease
- advanced age
- renal disease
- excessive anxiety
What’s non ionic contrast media
Lower toxicity and lower osmolality than ionic media
Acute reactions to IV media occur within one hour of administration
They can even be delayed reactions that can occur between one hour to a week after
What’s barium sulphate
Doesn’t act on cells, in which it doesn’t change what’s happening in the cells (function of cells remain)
It’s an Aqueous suspension used to analyse the GIT
Explain the contrast agents used for MRI
They’re carried free in plasma with little protein binding
Rapidly enter the extracellular fluid and intravascular space
They don’t penetrate the intact blood-brain barrier
Excreted via Kidneys
Adverse reactions are very uncommon
How’s a drug actually developed in pharmacology?
Stages
- in vitro testing (testing in testtubes and strains)
- in Vivo animal tests looking for acute effects
- in vivo animal tests looking for chronic effects (ie. toxicity, carcinogensis , teratogenicity (birth defects)
- human trials
Explain the phases going through during the human trials of drug testing
Phase 1 = pharmacodynamics (interaction between drug and receptor) and pharmacokinetics (drug transportation) in healthy people
Phase 2 = studies to determine best dose ie. special cases like renal failure
Phase 3 = clinical trials (testing drug on 1000 people sample)
Phase 4 = post marketing surveillance
How do you register a drug to be available to the wider population?
Has to be added to Australian register of therapeutic goods marinated by Therapeutic goods administration
Covers
- medicines (ie. prescription drug, vaccines, OTC medicines, some complementary medicines(might not be so safe))
- medial devices (X-RAY MACHINE, CT, MRI)
Can prescribed drugs be advertised?
No. Only OTC drugs like Panadol and all that
