Block 1 Foundations of Medicine Flashcards
Atropine
Class: Antimuscarinic agent
Mechanism: Inhibits muscarinic ACh receptor
Effect: Stops bradycardia or asystole
Betamethasone
Class: A glucocorticoid receptor agonist
Mechanism: forms a complex, which moves to nucleus, binds to DNA, causing gene transcription alteration, causing production of lipocortins, inhibiting phospholipase A2, reducing biosynthesis of prostaglandins and leukotrienes
Effect: anti-inflammatory, immunosuppressive and anti-mitogenic
Digoxin
Class: A cardiac glycoside
Mechanism: inhibits Na-K-ATPase membrane pump, increasing intracellular sodium, causing sodium calcium exchanger (NCX) to pump in more Ca2+
Effect: used to treat congestive heart failure and supraventricular arrhythmias
Edrophonium
Class: Acholinesterase inhibitor
Mechanism: inhibits acetylcholinesterase, prolonging action of ACh
Effect: used in cardiac arrhythmias and in diagnosis of myasthenia gravis
Ethanol
Class: Cellular Depressant
Mechanisms:
1) binds directly to receptors for ACh, serotonin, GABA and NMDA
2) anti-infective role - acts as a dehydrating agent that disrupts the osmotic balance across cell membranes
Effects:
Sedation - mediated via binding to GABA receptors and glycine receptors (alpha 1 and 2 subunits)
Ethinylestradiol
Class: Oestrogen Nuclear Hormone Receptor Agonist
Mechanism: interacts with oestrogen receptors. When bound, the receptor enters the nucleus to regulate gene transcription. Increases hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG) and suppresses follicle-stimulating hormone (FSH) from anterior pituitary
Effects: During menstruation, increased oestradiol causes maturation and release of egg, including thickening of uterus lining. Too much = acne, constipation, loss of sex drive and depression. Too little = retards bone growth
Used in combined oral contraceptive pill
Ketaconazole
Class: Broad spectrum anti-fungal agent (lanosine demethylase inhibitor)
Mechanisms:
- inhibits 14-α demethylase, a cytochrome P-450 enzyme which converts lanosterol to ergosterol, causing increased fungal cellular permeability
- inhibition of endogenous respiration
- interaction with membrane phospholipids
- inhibition of yeast transformation to mycelial forms
- inhibition of purine uptake
- impairment of triglyceride and/or phospholipid biosynthesis
Morphine
Class: Analgesic opiate agonist
Mechanism: unknown.
- mu-opioid receptors: mechanism of respiratory depression involves a reduction in responsiveness of brain stem respiratory centres to increases in CO2 tension and electrical stimulation
- GABA inhibitory interneurons: inhibits activity of these, limiting descending pain inhibition pathway. Without inhibitory signals, pain modulation can proceed downstream
Naloxone
Class: An opiate antagonist, pure narcotic antagonist
Mechanism: not clear, but thought to be able to antagonise all 3 opioid receptors; has strongest binding to Mu receptor.
Effects: prevents or reverses effects of opioids, such as respiratory depression, sedation and hypotension. Can reverse psychotomimetic and dysphoric effects of agonist-antagonists such as pentazocine
Rifampicin
Class: A broad spectrum bactericidal (DNA/RNA polymerase inhibitor)
Mechanism: inhibits DNA-dependent RNA polymerase, suppressing RNA synthesis and cell death. - Targets bacterial enzyme, not mammalian
Effects: restricted to TB, metabolized in liver, eliminated in bile and partially urine
Suxamethonium
Class: A depolarising nicotinic cholinergic receptor agonist
Mechanism: mimics ACh at neuromuscular junction, but hydrolysed slower, causing prolonged depolarisation and therefore desensitisation and muscle relaxation
Effects: cannot be reversed and recovery is spontaneous
Tamoxifen
Class: A selective oestrogen receptor modulator (SERM)
Mechanism: binds to oestrogen receptor, leading to conformational change, altering expression of oestrogen dependent genes.
Prolonged binding to nuclear chromatin reduces DNA polymerase activity, impairs thymidine utilization, blocks estradiol uptake, decreasing oestrogen response.
Effects: estogenic and anti-estrogenic effects as it can bind to alpha and beta oestrogen receptors, and interacts with multiple co-repressors, or co-activators
Tubocurarine
Class: A neuromusclular blocker (nicotinic cholinergic receptor antagonist)
Mechanism: binds stero-selectively to nicotinic-cholinergic recpetors at autonomic ganglia, adrenal medulla, neuromuscular junctions and in the brain
Effects:
- stimulation (low doses)
- occurs mainly in cortex via locus ceruleus
- reward (high doses)
- exerted in limbic system
Paracetamol
Class: Analgesic and antipyretic compound
Mechanisms:
- indirectly inhibits COX
- Inhibits COX-3
- antipyretic effects due to effects on hypothalamus, resulting in peripheral vasodilation and sweating
Effects: analgesic, antipyretic, but lacks anti-platelet, anti-inflammatory and gastric ulcer effects
Pyridostigmine
Class: cholinesterase inhibitor
Mechanism: reversible competitive inhibition of AChase in synaptic cleft, leading to reduction in hydrolysis of ACh, prolonging its effects and increasing efficiency of cholinergic transmission in neuromuscular junction
Effects: doesn’t pass through blood-brain barrier as poorly absorbed in the gut. Used in treatment of myasthenia gravis and to reverse actions of muscle relaxants
