Pharmacodynamics Flashcards
What is the definition of pharmacodynamics?
What the drug (chemical) does to the body and how the body responds
Interaction between chemical compounds of the body and foreign chemicals
What are the 4 ways in which drugs tend to work?
1) replace missing chemicals/act as their substitutes
2) stimulate particular cell activities
3) slow down/inhibit particular cell activities
4) interfere with function of foreign cells
What are the 4 types of proteins drugs mainly exert their effects on?
1) receptors
2) enzymes
3) ion channels
4) carrier (transporter) molecules
Define receptor…
Protein molecule
Has a specific shape/3D structure
Only substances that fit precisely can interact (complementary)
Enable natural substances e.g. NT/hormones to influence activity of the cell- influence may be stimulate or inhibit process inside cell
What is a ligand?
Molecule/chemical that binds to a receptor
What are target cells?
Cells with the appropriate receptor to detect/respond to hormones, mediators and NT
Define specificity…
Ability of the drug to combine with one particle type of receptor
No drug acts with complete specificity- this causes unwanted side effects
Define efficacy…
Measure of the bound ligand to activate a response
Define affinity…
Interaction between drug and binding site
Closer the fit and greater number of bonds leads to higher affinity of the drug for the receptor
What is the effect of an Agonist drug?
Activate or stimulate their receptors
Trigger a response to increase or decrease cell activity
What is the effect of an Antagonist drug?
Block the access/attachment of body’s natural agonists (NT) to receptors
Prevent/reduce cell responses to natural agonists
Define agonist…
Mimic action of endogenous (naturally occurring) ligands
Define antagonist…
Block action of endogenous ligands
What is the function of a reversible competitive antagonist?
Competes with the agonist for the agonist binding site on the receptor- blocks it, stopping agonist binding
Increasing agonist conc. can overcome blocking effect , restoring response
What is the function of irreversible, competitive antagonists?
Forms covalent bonds to agonist binding site so block cannot be overcome
What are the functions of non-competitive antagonists?
Bind to a site other than agonist binding site
Often causes conformational change in receptor, reducing ability of the agonist to bind to its binding site- reduces response to agonist
What are the functions of alpha-receptors?
Associated mainly with increased contractibility of vascular smooth muscle and intestinal relaxation
What are the functions of beta-receptors?
Associated with vasodilation and relaxation of non-intestinal smooth muscle and cardiac stimulation
What is an enzyme?
A protein which acts as a biological catalyst
Controls rate at which reactions occur
Remain unchanged
What is the function of the active site?
Where chemical reactions occur
Where the enzyme interacts with its substrate
The prime target for drugs acting on enzymes
What is the function of non steroidal anti-inflammatory drugs (NSAIDS)?
Drugs that block activity of an enzyme
Inhibit enzyme cyclo-oxygenase (COX)- block its activity
What is the function of COX?
Responsible for formation of some important chemical mediators e.g. Prostaglandins- play key role in inflammation and pain
What is the function of acetylcholinesterase inhibitors?
Used to improve/stabilise symptoms of Alzheimer’s disease
Breaks acetylcholine in the synapse- if you inhibit breakdown of acetylcholine more NT would remain in synapse, enhancing memory
What is the function of Acetylcholine?
NT helping with memory and thinking
What are the functions of calcium channel blockers?
Act as vasodilators- blocking intracellular calcium required for contraction of arteriolar smooth muscle
Reduce aldosterone production (adrenal cortex)
Lowers BP
Slows HR
Reduce force of contraction in cardiac smooth muscle
Negative chronotrophic effect- atrial fibrillation possibly causing heart block
What does vasodilation cause in calcium channel blockers?
Causes reduction in peripheral vascular resistance- reduced BP
What are the functions of sodium channels?
Vital for propagation of AP along nerve cells
What happens if sodium channels are blocked?
Prevents sensation of pain
Delay in conductance, decrease in excitability and prevents sensations of pain
What are the functions of potassium channel blockers?
Prolongs repolarisation (going back to resting state)
What are the functions of potassium channel openers?
Used to rest hypertension and angina- relax smooth muscle- vasodilation
What is the function of GABA?
Most common NT
Acts to reduce excitability in CNS
Reduced signalling in the brain
Sedating NT
What are the functions of Benzodiazepines?
Act as modulators of GABA receptors, potentiating effect of the receptor
What is the function of Serotonin?
In the CNS it is a mood enhancer
Increasing levels in synaptic cleft available to bind to postsynaptic receptors causing mood enhancement
What is the function of Selective Serotonin Reuptake inhibitors?
Prevent reuptake of Serotonin from synaptic cleft back into the pre-synaptic neurone
