ICS - Pharmacology 2 Flashcards
Which routes of drug administration are local?
- Topical- Intranasal- Inhalation (can be systemic)- Transdermal (can be systemic)
Which routes of drug administration are systemic (enteral)?
- Oral- Rectal- Sublingual/buccal
What does enteral drug administration mean?
Absorbed from gastrointestinal tract
Which routes of drug administration are systemic (parenteral)?
- Intravenous- Intramuscular - Subcutaneous- Inhalation (can be local)- Transdermal (can be local)
Define first pass metabolism
Metabolism of a drug by the liver before being released into the systemic circulation - when drugs are administered orally
Define bioavailability
The proportion of drug given that enters the circulation and so can exert an effect on the body
Define agonist
Binds to a receptor to activate
Define antagonist
Binds to a receptor to prevent a reaction occurring
What is the difference between competitive and non-competitive antagonists?
Competitive antagonists bind directly to the active site of a receptor to prevent other things from binding whereas non-competitive antagonists bind to another part of the receptor (not the active site) to change the shape of the active site and prevent other things from binding
Define selectivity
The ability of a drug to discriminate between and only affect certain cell populations
Define specificity
The capacity of drug to trigger a response
What is the difference between endogenous and exogenous ligands?
Exogenous - originates outside body e.g. drugs Endogenous - originates inside body e.g. hormones/neurotransmitters
Name 4 receptors that drugs target
- Ligand gated ion channels2. G protein coupled receptors3. Kinase linked receptors4. Cytosolic/nuclear receptors
What are ligand gated ion channels?
Membrane proteins that allow ions to pass through so that the cell undergoes a shift in electric charge distribution (e.g. nicotinic ACh receptor)
What are G protein coupled receptors?
Integral membrane proteins used to convert extracellular signals into intracellular responses (e.g. muscarinic and beta-2 adrenoceptor)
What are kinase linked receptors?
Enzymes that catalyse the transfer of phosphate groups between proteins (e.g. receptors for growth factors)
What are cytosolic/nuclear receptors?
Receptors that modify mRNA/protein synthesis (e.g. steroid receptors - steroids affect transcription)
Define affinity in drug action
How well a ligand binds to a receptor
Define efficacy in drug action
How well a ligand activates a receptor (how well it induces a conformation change)
Describe enzyme inhibitors
Molecules that bind to an enzyme and usually decreases its activity. There are reversible and irreversible inhibitors e.g. statins and ACE inhibitors
What are uniporters
Membrane transport proteins that transport individual molecules into a cell
What are symporters?
Membrane transport proteins that transport two molecules across a membrane in the same direction
What are antiporters?
Membrane transport proteins that transport two molecules across a membrane in different directions
What are ENaC inhibitors/blocking used for?
Problems relating to heart failure
What are ENaC inhibitors/blockers?
Epithelial sodium channel inhibitors. Decrease reabsorption of Na+ ions at the collecting ducts. Helps to prevent the loss of potassium and lower blood pressure
Give an example of an ENaC inhibitor/blockers
Amilioride
What are calcium channel blockers used for?
Lowering blood pressure
What are calcium channel blockers?
Prevent influx of calcium into smooth/cardiac muscle cells which causes vasodilation and decreased peripheral vascular resistance
Give 2 examples and 3 side effects of calcium channel blockers
- Amlodipine (vasodilates and doesn’t decrease heart rate - non rate limiting)- Verapamil (vasodilates and decreases heart rate - rate limiting)- Constipation, dizziness, fatigue
What are sodium channel blockers used for?
Local anaesthetics, anticonvulsants etc.
What are sodium channel blockers?
Prevent influx of sodium into cells to slow depolarisation and so reduce conduction velocity
Give an example of sodium channel blockers
Lidocaine (local anaesthetic)
What are potassium channel blockers used for?
Treating arrhythmias and type II diabetes
What are potassium channel blockers?
Block ATP-dependent potassium channels so that they cannot open. This increases calcium influx and prolongs action potentials and also triggers insulin secretion in pancreatic beta cells
What are GABA inhibitors used for?
Sedatives (depress central nervous system)
What are GABA inhibitors?
Block neurotransmitter GABA from binding to GABA A receptors. Binds to GABA A receptors to cause prolonged opening of Cl- channel and increased influx of Cl- ions. This causes the action potential to decrease and inhibits activity
Give an example of GABA inhibitors
Barbiturates e.g. phenobarbital
What are sodium pump inhibitors used for?
Problems relating to irregular heartbeats (e.g. atrial fibrillation and atrial flutter)
What are sodium pump inhibitors?
A.k.a digitalis glycosides. Inhibit Na/K ATPase required for sodium pump (3Na+ out, 2K+ in) which increased intracellular Na+ and therefore intracellular Ca2+. This lengthens the cardiac action potential and so decreases heart rate
Give an example of sodium pump inhibitors
Digoxin
What are proton pump inhibitors used for?
Reducing gastric acid production (for heartburn/indigestion)
What are proton pump inhibitors?
Prevent exchange of K+ from intestinal lumen with cytoplasmic H+ in order to block gastric acid secretion
Give 2 examples and 5 side effects of proton pump inhibitors
- Omeprazole, lanzoprazole- Headaches, dizziness, nausea, constipation/diarrhoea, abdominal pain
Define pharmacokinetics
Action of the body on a drug
Define pharmacodynamics
Action of a drug on the body
What are the 4 steps of pharmacokinetics?
- Absorption2. Distribution3. Metabolism4. Excretion
What are 5 factors that affect absorption of a drug?
- Motility- Acidity- Solubility- Complex formation- Direct action on enterocytes
What are 7 factors that affect distribution of a drug?
- Blood flow- Capillary permeability- Protein binding - Volume of distribution- Size of molecules- How lipophilic/phobic a drug is- Blood brain barrier/blood testicle barrier
Describe metabolism of a drug (pharmacokinetics)
- Lipid soluble drugs cannot be excreted by the kidney (liver metabolises them so they can be)- Liver makes drug hydrophilic and then polar