Mechanism of Action of Para Drugs Flashcards
Adrenaline 1:1000
Highly potent adrenergic agonist
• Sympathomimetic agent
• Alpha & beta 1 & beta 2 binding at adrenoreceptors
• Alpha excitatory – pupil dilation, vasoconstriction of blood vessels
• Beta 1 – heart (excitatory) intestinal & smooth muscle (inhibitory) (chronotrophic, inotrophic effect)
• Beta 2 – bronchial dilation, vascular & uterine smooth muscle; inhibitory (inhibits histamine release, causes bronchodilation)
Definitions
Adrenergic agonist - mimics the NS
Chronotrophic - increases heart rate
Inotrophic - increases contraction
Aspirin
Is an NSAID (inhibits prostaglandin synthesis)
• Enzyme inhibitor (COX) - reduces rate of enzyme catalyst reaction
• Anti-inflammatory; anti-pyretic, anti-platelet
• Reduces platelet aggregation (part of clotting) by preventing the creation of thromboxane (also called TXA2 & is a prostaglandin)
• Inhibits COX 1 and COX 2 irreversibly
Anti inflammatory - reduce swelling
Antipyretic - reduce fever
Antiplatelet - prevents blood clotting
Entonox
Moa not well understood
?modulates pain receptor process in the spinal cord
Glucagon
Stimulates glycogenolysis and gluconeogenesis to raise blood glucose
GTN
Causes peripheral vasodilation, especially in veins, & lowers pre-load & dilation of coronary arteries
• Lowering pre-load reduces distension of heart & decreases oxygen demand on heart
• Metabolism of GTN leads to the production of nitric oxide (NO)
• NO activates guanylyl cyclase increasing cGMP in vascular smooth muscles cells - increasing vasodilation
• Given sublingually to avoid first pass metabolism
cGMP - second messenger molecule that modulates downstream effects, ie vasodilation, pupil dilation, neurotransmission
Hydrocortisone
Corticosteroid - affects gene expression in nucleus and production of arachidonic acid and prostaglandins
Role in salt & water balance, BP blood glucose, anti- inflammatory
Arachidonic acid - promotes repair and growth of skeletal muscle tissue
Prostaglandins - lipids at the site of damage or infection that control inflammation, blood flow and induction of labour
Ipatrpium bromide
Anticholinergic at muscarinic receptors (parasympathetic NS)
• Muscarinic antagonist
• Reduces parasympathetic nervous system action on the bronchioles (prevents smooth muscle from contracting)
• Results in decrease in formation of cGMP which affects intracellular calcium levels (increase) & results in decreased smooth muscle contraction
Anticholinergic - blocks and inhibits the neurotransmitter acetylcholine
Salbutamol
Selective B2 adreno-receptor agonist
• Activation of beta-2 adrenoreceptors relaxes smooth muscle by increasing cAMP ( which increases the binding of infra cellular calcium to the cell membrane) & activating a protein kinase. This inhibits muscle contraction.
Midazolam
Has anxiolytic, hypnotic, muscle relaxant, anticonvulsant & amnesic actions
• Benzodiazepine (sedative)
• Acts on central GABA receptor ( the main CNS inhibitory neurotransmitter )
• Enhances GABA inhibition in CNS
• CNS depressant - slows down functions of the brain and relax muscles
Naloxone
Competitive antagonist at mu opioid receptor - which reverses and blocks the effects of other opioids
• Very high affinity – higher than most opiates
Paracetamol and Ibuprofen
Ibuprofen – NSAID, non-selective COX inhibitor
Paracetamol – precise mechanism of action unknown - thought to inhibit COX 1 and 2 INDIRECTLY which are involved in prostaglandin synthesis
• Also been suggested that COX3 is inhibited too
NSAIDs - All inhibit cyclo-oxygenase (COX) enzyme
Results in inhibition of prostaglandin synthesis, this inhibition in the gastric mucosa causes GI damage
Chlorphenamine
Antihistamine that antagonises histamine that is released during allergic reactions
Anticholinergic properties (drowsiness, dry mouth etc.)
