pharmacology basics Flashcards
what are the 6 rights of drug administration?
Right Patient Right medication Right Dose Right Route Right Time Right Documentation
what is pharmacology?
the science of the properties of drugs and their effect on the body
What is a drug/medicine?
any chemical agent that can have a biological response on the body - therapeutic or adverse
what names are used for drugs?
trade name
generic name
What are the medical sources of drugs/medicines?
plants
animal, microorganisms or by body
synthetic
complementary medicines
what acronym is used for drugs over the counter and prescription only?
drugs over the counter (OTC) prescription only (POM)
Name the two classifications that can be used for drugs
Pharmacological - how they work (beta blockers)
Therapeutic - what they do (anti-hypertensive)
What are we legally obligated to do as professionals in regard to drugs?
use standards/ guidelines
confirm accuracy of script
use knowledge and competence
have understanding of the drug
what should the targets of drugs be?
needs to bind to specific targets - the more specific the drug is to the target the better it works
What mechanism is used to describe the binding of drugs to their targets?
lock and key mechanism
name five targets which drugs use
membrane
nucleus - drugs need special properties to enable it to reach nucleus
cytosol
enzymes - drug slows/ speeds up reactions
foreign protein
name three areas with in the membrane that drugs can target
membrane receptors
ion channels
carrier molecules/ pumps
what does a drug influence when it targets the nucleus?
DNA production
What are drugs used to target?
bacteria
virus (retrovirals)
fungus
worms - ameboa
Give examples of 2 drugs which bind to enzymes
Aspirin - COX enzyme
Viagra - increases blood flow
Give examples of 3 drugs which bind to membrane receptors
Salbutamol - dilate airways
Beta blockers
anti-histamine - blocks effect of histamine
Give examples of 3 drugs which bind to ion channels
Local anaesthetics - blocks pain response
Benzodiazepines (valium) - blocks fluoride transport to brain
Give examples of 2 drugs which bind to carrier molecules (or pumps)
Omeprazole - blocks acid production
Cocaine - keeps noradrenaline active
Give an example of a drug which bind to DNA
Steroids - reduces inflammation
Give an example of a drug that binds to a foreign protein
Penicillin
what is an agonist?
Activates receptor
binds to a receptor and mimics chemicals in body
what is an antagonist?
doesn’t activate receptor but blocks it.
binds to receptor and stops chemicals producing response
what happens when a drug binds to a receptor?
drug binds
activation of 2nd messenger
cascade of enzyme reaction
results in response
describe some cellular responses to drugs
muscle cell - contraction glands - secretion Muscle - excitation Nerve - excitation/ inhibition Tumour cell - interrupt cell cycle
Explain how steroids can target the nucleus
steroids are based on structure of cholesterol which is lipid soluble, therefore passes through membrane
explain the term potency and the effect that high potency has
Potency means that it has a high affinity with the receptor - the shape matches well
High potency means that a small dose is required for response
in children is potency higher or lower?
higher
Explain the steps involved in drug deposition
Intake Absorption Distribution - drug can go to target and be directly excreted or be metabolism before drug cell interaction Drug Cell Interaction Metabolism Excretion
List 8 way in which drugs can be administered
Injection Oral Rectal Topical Vaginally Inhalation Transdermal - patches Sustained release
name 6 types of injection
epidural - into epidural space intradermal - few layers of skin intramuscular subcutaneous - below subcutaneous layer intravenous - (IV) intrathecal - into subarachnoid space
which is the most common route for drug administration?
oral
list some advantages of oral drugs
easy for patients to self administer
well absorbed - small intestine
suspension or pill
list some disadvantages of oral drugs
can interact with stomach acid - degradation
not suitable in vomiting/ diarrhoea/ frequent gastric emptying
list some advantages of topical drugs
convenient
overdose risk minimised
local effect
list some disadvantages of topical drugs
poorly absorbed
negative effect on skin
give 3 examples of transdermal drugs
HRT patches
nicotine patches
angina patches
list some advantages of transdermal drugs
long lasting
constant level of drug in blood
wide range of patients
high potency
list some disadvantages of transdermal drugs
variable absorption
drug needs to be very lipid soluble to cross cell membrane
rectal administration can produce a local or systemic effect?
both
what patient would it be useful to use rectal administration?
a vomiting patient
is rectal administration fast or slow acting?
fast
give 4 examples of drugs which could be administered rectally
analgesics
diazepam
prednisolone
anti-fungals
why does inhalation of drugs cause a rapid change in plasma concentration?
lungs have huge surface area and good blood flow
does inhalation of drug cause a local or systemic effect?
both
what is a disadvantage of inhalation of drugs?
drug doesn’t always reach target
what are the advantages of parenteral routes
rapid action
bypass stomach
patient controlled syringe driver
what are the disadvantages of parenteral routes
administration by a trained person
extreme care needed to deliver correctly
accidental overdose more likely
painful
what is contained within a medicine?
active drug and excipients
what are excipients used for?
help protect drug from gastric juices
provide sustained release - this impacts on bioavaliablity
explain the steps involved in dissolution of oral drugs
tablet
granules to fine particles - in GI tract
solution - absorption in stomach and mainly SI
explain the steps involved when lipid soluble drugs cross the cell membrane
they move via diffusion from the gut to epithelial cells to bloodstream
what happens to water soluble drugs?
they remain in the gut and can not cross the epithelial cells to enter the blood
give 3 examples of drugs which can be given by inhalation
nitrous oxide
GTN
salbutamol
how do most drugs cross the cell membrane?
via passive diffusion
what ways other than passive diffusion can drugs cross the cell membrane?
aquaporin’s
endocytosis - eg. insulin
facilitated transport - drugs move down conc. gradient via protein channels (no ATP needed)
active transport - drugs move against conc. gradient (ATP needed)
what is bioavailability?
the amount of drug which ultimately enters the bloodstream
what is the maximum bioavailability?
1 - only happens in IV administration
explain what happens during first pass metabolism
liver responsible for metabolism
drug absorbed in SI then goes to liver
liver degrades drug causing low bioavailability
why is angina drug administered under the tongue?
to bypass first pass metabolism
what is distribution?
movement of drug to the body’s tissues
what factors affect distribution?
lipid solubility
blood flow to organ - higher blood flow = better distribution
binding of drug to protein
what is the blood flow to the liver and kidneys?
liver - 680 b/flow
kidneys - 3,333 b/flow
which organ has the highest blood flow
kidneys
why does the drug binding to protein affect distribution?
when drug binds to protein it is too large to cross the cell membrane or bind to target site
what is polypharmacy?
taking more than four drugs - drug interaction could be caused
why is it important to concerned drug interactions when using drugs that bind to proteins?
if taking two drugs that bind to proteins the drugs will not work together
regular testing is needed to establish efficacy
what is metabolism?
drug removal
what needs to be adjusted in patients with liver disease?
doses must be adjusted as excretion of drug is less effective
most drugs are lipophilic, how are lipophilic drugs excreted?
lipophilic drugs will recirculate in body - they need to become water soluble to be excreted
how are lipophilic drugs converted to become water soluble
enzyme mediated conversion - carried out in the liver using hepatocytes (smooth ER)
where does metabolism occur in the body?
kidneys liver GI tract brain plasma
how many phases does metabolism occur in?
2 - I and II
describe what happens in phase I metabolism
(Producing a metabolite)
modify chemical structure of drug
make drug slightly more water soluble
preparing drug for phase II
what usually happens to drugs following phase I metabolism?
drug is usually less active than parent drug
what are pro drugs?
sometimes following phase I metabolism drugs become more chemically active (pharmacological activation) these are called pro drugs
what is pharmacological activation?
a drug that become chemically active following phase I metabolism
give two examples of pro drugs
prednisone - prednisolone
codeine - morphine
(second drugs are the metabolites)
what happens during phase II metabolism?
‘conjugate’ drug to large molecule (eg. amino acid)
what generally happens to drug following phase II metabolism?
water soluble easily excreted increased molecular weight inactive (pharmacological inactivation) reduced affinity to binding site
what can occur due to drug interactions?
drug metabolism could be induced or inhibted
what would happen if drug metabolism was induced?
could speed up metabolism of another drug meaning it is metabolised too quickly to work
what would happen if drug metabolism was inhibited?
stops drug from being metabolised quickly - thus producing toxic concentration
give an example of a drug interaction
fluoxetine (Prozac) and grapefruit juice
what is excretion?
removal of drug metabolites and water soluble drugs
via what routes can excretion of drugs occur?
urine/ bile - often
faeces - less often
lungs / skin - sometimes
what factors increase drug excretion?
increased blood flow to kidneys
reduced plasma protein binding
what factors can increased or decrease drug metabolism?
genetic differences
drug interactions
what is the therapeutic response to drugs related to?
level of drug in plasma
what is the half life?
time it takes drug to drop by 50% from peak level
how does half life influence drug dosing?
most likely that next dose of drug will be given after 1 half life (eg. HL 4hrs - next dose 4hrs)
what is a therapeutic window?
window in which we see a therapeutic effect
what precautions would you take if the drug to be given had a narrow therapeutic window?
not much difference between low and upper level
patients often need therapeutic concentration test to check drug within safe limits
explain how the half life is determined
give drug
take measurement regularly and plot on graph
work through this example to determine how much drug would be in the body after 10hrs. patient takes 20mg of drug with half life of 2hrs
2hrs - 10mg 4hrs - 5mg 6hrs - 2.5mg 8hrs - 1.25mg 10hrs - 0.625mg (drug amount now negligible)
97% of drugs are eliminated from the body after how many half lives?
5
what would be required if a patient needed a drug to reach the therapeutic range quickly?
a loading dose would be given
what is a compound medicine and give an example?
2 or more meds in one tablet (‘co’ used)
co-codamol - codeine / paracetamol
