How Drugs Act 1 Flashcards
(27 cards)
Explain the meaning of pharmacology.
The branch of medicine and biology concerned with the study of drug action.
More specifically, it is the study of the effects of drugs on the function of living organisms.
Define receptor.
In pharmacology, it describes protein molecules whose function is to recognise and respond to endogenous chemical signals (permanently or transiently).
Other macromolecules with which drugs interact to produce their effects are known as drug targets.
Define ligand.
A molecule which produces a signal by binding to a site on a target protein.
Define second messenger.
Intracellular signalling molecules released by the cell in response to exposure to extracellular signalling molecules that act to transmit signals from a receptor to a target.
Define agonist.
A drug that produces a positive effect (boosts) when bound to a receptor.
Define antagonist.
A drug that reduces the effect of an agonist at a given receptor.
Explain the concept of irreversible binding.
An irreversible antagonist binds covalently to the receptor and can’t be displaced by either competing ligands or washing.
Give some examples of irreversible binding.
Aspirin irreversibly inhibits cyclooxygenase (COX) by acetylation of an amino acid serine residue, and thus blocks the subsequent biosynthesis of prostaglandins and thromboxane.
Explain the concept of reversible binding.
A reversible antagonist binds non-covalently to the receptor, therefore can be ‘washed out’.
Explain the concept of competitive binding.
A competitive antagonist binds to the same site as the agonist but doesn’t activate it, thus blocks the agonist’s action.
Explain the concept of non-competitive binding.
A non-competitive antagonist binds to an allosteric (non-agonist) site on the receptor to prevent activation of the receptor.
What is efficacy?
E_max
The maximum response achievable from a drug.
What is potency?
The dose of drug required to produce a specific effect of given intensity (depends on the efficacy and affinity).
What is EC50?
The concentration of a drug that induces a half-maximal response.
It is useful for comparing different drugs that produce quantitively similar effects.
Name the four types of receptor.
- Ligand-gated ion channels
- G-protein-coupled receptors
- Receptor kinases
- Nuclear receptors
Describe ligand-gated ion channels. (location, effector, coupling, examples and structure)
Location: membrane
Effector: ion channel
Coupling: direct
Examples: nicotinic acetylcholine receptor and GABA_A receptor
Structure: oligomeric assembly of subunits surrounding central pore
Describe G-protein-coupled receptors (location, effector, coupling, examples and structure)
Location: membrane
Effector: channel or enzyme
Coupling: G-protein
Examples: muscarinic acetylcholine receptor and adrenoceptors
Structure: monomeric or oligomeric assembly of subunits comprising seven transmembrane helices with intracellular G-protein-coupling domain
Describe receptor kinases (location, effector, coupling, examples and structure)
Location: membrane
Effector: protein kinases
Coupling: direct
Examples: insulin, growth factors and cytokine receptors
Structure: single transmembrane helix linking extracellular receptor domain to intracellular kinase domain
Describe nuclear receptors (location, effector, coupling, examples and structure)
Location: intracellular
Effector: gene transcription
Coupling: via DNA
Examples: steroid receptors
Structure: monomeric structure with separate receptor- and DNA-binding domains
Define drug.
Any man-made, natural or endogenous chemical substance of known structure, other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect.
How much does the UK spend on medical and non-medical drugs?
Medical: £18bn p.a.
Non-medical: £30bn p.a. (£500 pp)
Explain specificity in drugs.
Specificity is reciprocal, so individual classes of drug bind only to certain targets, and individual targets recognise only certain classes of drug.
However, no drugs are completely specific, and in many cases increasing the dose of a drug will cause it to affect targets other than the principal one, leading to side effects.
Give some examples of receptor targets.
Salbutamol (B2 adrenoceptors)
Sildenafil (PDE5)
Ibuprofen (COX-2)
Give some examples of non-receptor targets.
Plant sterols (cholesterol lowering)
Ammonium hydroxide (anti-pruritic/itching)
Alcohol (sedative/hypnotic)
