Session 2 - Pharmacodynamics Flashcards
Define drug action
Interaction at cellular level between a drug and cellular components.
Define drug effect
The response resulting from the the drug action which may affect local function or wider body function.
Explain specific drug action
Effects produced by interaction of the drug with a specific site, either on the cell membrane or inside the cell. Eg receptor activation
Name 4 types of drug action
- Stimulation
- Inhibition/Depression
- Replacement
- Cytotoxic
Explain and give an example of the drug action “stimulation”
Selective enhancement of the level of activity of specialised cells
Eg adrenaline and heart
Explain and give an example of the drug action “inhibition/depression”
Diminution of activity of specialised cells
Eg diazepam
What are type of structure is the cell membrane
Phospholipid bilayer
Name 3 targets of drug action
- Receptors
- Enzymes
- Transport or uptake inhibitors
Explain how drugs interact with receptors
Specific proteins situated on cell membranes .
Each are able to react with ligans (eg hormones, neurotransmitters and nutrients).
Drugs with similar chemical shape bind to these receptors. Eg adrenaline and the heart by mimicking the shape of the ligans
What are ligans
Endogenous substances such as hormones and neurotransmitters
Receptor activation - name 3 ways in which ligands can act
- Agonist
- Antagonist
- Partial Agonist
What is an agonist ?
Drugs that occupy receptors and activate them
What is an antagonist ?
Drugs that occupy receptors but do NOT activate them. Antagonists block receptor activation from agonists.
Name an antagonist and how it works
Beta blocker (bisoprolol) blocks receptors so that a ligans (adrenaline) can not activate the receptor which in turn works to lower blood pressure.
Explain a partial agonist
Only has a partial efficiency at the receptor, triggers a response lower than a full agonist at tech receptor
Example of an agonist action
Activates or enhances cellular activity
Morphine and insulin
Define affinity
The force of attraction between the drug and a receptor
Define efficacy
Drugs ability to activate a response once bound to the receptor
Difference between potency and efficacy
Potency is how much drug is needed to produce an effect that’s required.
Efficacy is the capacity of drug to activate a receptor.
If two drugs are in competition for the same receptor which is going to win ? This is known as competitive antagonism
The one with the higher affinity
Non competitive antagonism
Counter the effect of another drug or natural chemical but not competing for the receptor
What acid is involved in response to an inflammatory response ?
Arachidonic acid
What are enzymes ?
Biological catalysts, they speed chemical reactions and are not changed them selves.
Explain ACE inhibitor hypertension medicine in terms of pharmacodynamics
Renin is released by the kidneys.
Renin converts angiotensinogen produced by the liver to angiotensin 1.
Angiotensin converting enzyme (ACE) forms angiotensin 2 which causes the arteries to narrow.
ACE inhibitors stop the ACE activity, and therefore relaxes the arteries and lowers blood pressure.
What is activated in response to arachidonic acid ?
Cox- 1 enzyme
Cox - 2 enzyme
Explain the cyclooxygenase pathway
Arachidonic acid is realised in response to irritation or injury. In response to arachidonic acid COX 1 and COX 2 catalyse the formation of prostaglandins within the body.
Cox 1 catalyses prostaglandins that are responsible for what ?
Name 3
Homeostatic effects
1 - renal homeostasis
2 - Gastric mucosal production
3 - platelet function
Cox 2 is responsible for catalysing prostaglandins that are responsible for what ?
Name 3
Inflammatory effects
1- pain
2- inflammation
3- fever
Which enzyme is expressed constantly ? Cox 1 or cox 2 and why ?
Cox 1 - as it is responsible for homeostatic effects
Which enzyme is only expressed during irritation or injury ? Cox 1 or cox 2 and why ?
Cox 2 as it has inflammatory effects.
Name the 3 targets for drug action.
- Receptors
- Enzymes
- Transport or uptake inhibitors
Define an enzyme
A biological catalyst catalyst that increases the chemical reaction in the body.
Define receptors
A macro molecular structure found within a cell or on its plasma membrane that is able to react with ligans.
Explain transport/uptake inhibitors in terms of SSRIs
Serotonin is released into the synaptic cleft.
Under normal circumstances, some of the serotonin is taken back into the presynaptic nerve ending.
SSRIS inhibit this mechanism therefore serotonin levels are increased in the synaptic cleft and more serotonin is available to bind to receptors
What does SSRIs stand for.
Selective serotonin reuptake inhibitors.
Name to SSRIS
Fluoxetine and citalopram
Define competitive antagonism in terms of morphine naloxone.
Naloxone has a higher affinity to receptors than morphine therefore naloxone can reverse the effects of morphine on the body.
Define non competitive antagonism.
Counter the effect of another drug or natural chemical but not competing for the same receptors.
