Second Year Drugs

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Anonymous
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302366
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Second Year Drugs
Updated:
2015-05-08 10:41:56
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Pharmacology
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Vet Med - Second Year - Drug mechanisms of action
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  1. What is the mechanism of action of local anaesthetics?
    Na+ channel blockers, preventing initiation and conduction of APs.
  2. Are local anaesthetics weak acids or bases?
    Weak bases
  3. What form of local anaesthetics is active: charged or uncharged?  What form can cross the axonal membrane?
    • Charged
    • Uncharged
  4. What is the mechanism of action of NSAIDs?
    NSAIDs inhibit cyclooxygenase which decreases the production of prostaglandins and thrombaxanes.
  5. What are the clinical classifications of NSAIDs?
    • Non-selective COX inhibitors (COX1 and COX2)
    • Preferential COX2 inhibitors (COX2 first but will then bind to COX1)
    • Selective COX2 inhibitors (only bind to COX2)
  6. What is the mechanism of action of neuromuscular blocking agents?
    They are competitive antagonists at the nicotinic ACh receptor.
  7. How many sites must be blocked for neuromuscular blocking agents to have their effect?
    ~80%
  8. What is the mechanism of action of organophosphates?
    Inhibit acetyl cholinesterase
  9. What is the mechanism of action of pyrethrins and pyrethroids?
    Act on presynaptic Na+ channels so the insect dies of flaccid paralysis
  10. What are pyrethroids?
    Synthetic pyrethrins
  11. What species is pyrethrin contraindicated in?
    Cats - it is toxic
  12. What is the mechanism of action of avermectins and milbemycins?
    Act on GABA and/or glutamate gated chloride channels
  13. What species is ivermectin contraindicated in?
    • Dogs with the MDR1 mutation e.g. collies
    • Kittens
    • Turtles and tortoises
  14. What is the mechanism of action of amidines (amitraz)?
    Octopamine receptor antagonist and alpha2 receptor agonist.  Leads to insect hyperactivity and detatching behaviour, reduces egg hathability, reduces fecundity and inhibits oviposition
  15. What animals is amitraz contraindicated in?  What is the antidote?
    • Cats, chihuahuas and dogs in heat stress.
    • Alpha2adrenoreceptor antagonist eg atipamezole.
  16. What is the mechanism of action of cyromazine and methoprene?
    Effect deposition of chitin in cuticle (cyromazine) and juvenile growth hormone (methoprene).  They are insect growth regulators.
  17. What is the mechanism of action of benzoyl urea derivatives?
    Inhibits chitin synthase in fleas. Also kills eggs and larvae.
  18. What is the mechanism of action of fipronil?
    GABA and gluatamate gated chloride channel antagonist
  19. What is the mechanism of action of neonicotinoids?
    Block nicotinic receptors which inhibits cholinergic transmission causing paralysis and death
  20. What is the mechanism of action of metaflumizone?
    Blocks Na+ channels resulting in paralysis
  21. What is the mechanism of action of oxadiazine insecticides?
    Na+ channel blocker (contact insecticide, requires bioactivation)
  22. What is the mechanism of action of allyamines?
    Inhibit ergosterol biosynthesis via inhibition of squalene epoxidase
  23. What is the mechanism of action of azoles?
    Inhibit cytP450-dependent 14-sterol de-methylase
  24. What is the mechanism of action of polyenes (amphotericin B)?
    Bind to ergosterol and disrupt the osmotic integrity of the cell membrane
  25. What is the mechanism of action of glucan synthase inhibitors?
    Block synthesis of beta (1,3) glucan
  26. What is the mechanism of action of antimetabolites?
    Disrupt protein synthesis
  27. What is the mechanism of action of griseofluvin?
    Selectively deposited in newly formed keratin, inhibits mitosis, disorganises the spindle microtubules
  28. What is the mechanism of action of opioids?
    Opioids bind to receptors in the CNS and PNS to cause either: inhibit adenylate cyclase and decrease cAMP, increase opening of K+ channels, or decrease opening of Ca2+ channels
  29. What is the mechanism of action of ketamine?
    NMDA antagonist or blocks channel
  30. What is the mechanism of action of general anaesthetics?
    Enhances inhibitory action of GABA by binding to an allosteric site and promoting binding of GABA to GABA receptors
  31. What is the mechanism of action of benzodiazepines?
    Increase the affinity of GABA for its receptor
  32. What is the mechanism of action of alpha adrenoreceptors?
    Presynaptic inhibition of neurotransmitter release and postsynpatic inhibition of smooth muscle relaxation
  33. What is the mechanism of action of phenobarbitone?
    Facilitates action of GABA, decreases neuronal excitability through interaction with glutamate receptors and inhibits voltage gated Ca2+ channels
  34. What is the mechanism of action of potassium bromide?
    Bromide crosses the chloride channel in preference to chloride.  It therefore facilitates the effect of neurotransmitters acting on GABA by hyperpolarising the cell membrane.
  35. What is the mechanism of action of imepitoin?
    Partial agonist at benzodiazepin recognition site of GABA receptor.  Also has weak Ca2+ channel blocking effect.
  36. What is the mechanism of action of diazepam?
    Acts directly on a specific receptor activating GABAa channel hyperpolarising the cell membrane
  37. What is the mechanism of action of tetracyclines?
    Reversibly bind to the 30s subunit on the bacterial ribosome to inhibit bacterial protein synthesis
  38. What is the clinical use of tetracyclines?
    Mixed bacterial infections
  39. Are tetracyclines bacteriostatic/bactericidal?
    Bacteriostatic
  40. What are minocycline or doxycycline?
    Semi synthetic derivatives of tetracycline
  41. What is the mechanism of action of macrolides?
    Act at the translocation stage of protein synthesis to inhibit it
  42. Why are macrolides selectively toxic?
    As they only bind to bacterial ribosomes
  43. Are macrolides bacteriostatic/bactericidal?
    Bacteriostatic
  44. What is the mechanism of action of fluoroquinolones?
    Bind to Topomerase IV and DNA gyrase to inhibit bacterial DNA replication.
  45. How do fluoroquinolones enter pathogens?
    Through porins
  46. Are fluoroquinolones bacteriostatic/bactericidal?
    Bactericidal
  47. What is the mechanism of action of amantadine/rimantadine?  What virus do they act on?
    Ion channel blockers.  Act on Influenza A.
  48. What is the mechanism of action of AZT?  What virus does it act on?
    Reverse transcriptase inhibitor.  Acts on retroviruses.
  49. What is the mechanism of action of Aciclover?  What virus does it act on?
    DNA polymerase inhibitor.  Acts on herpes simplex.
  50. What is the mechanism of action of 'tamiflu'?  What virus does it act on?
    Neurominidase inhibitor.  Acts on influenza A and B.
  51. When controlling bronchial tone, what is the mechanism of action of B2-adrenoreceptor agonists?
    Stimulate adrenergic pathways which leads to smooth muscle relaxation
  52. When would adrenaline be used to control bronchial tone?
    Only in emergency treatment of life threatening bronchoconstriction
  53. When controlling bronchial tone, what is the mechanism of action of anticholinergic/antimuscarinic  drugs?
    Block endogenous parasympathetic tone
  54. When controlling bronchial tone, what is the mechanism of action of methylxanthines?
    PDE inhibitors (increases cAMP which causes bronchial smooth muscle relaxation), decrease inflammatory mediators and inhibit adenosine
  55. Describe the normal endogenous control of corticosteroids
    Hypothalamus produces CFR which is transported to the anterior pituitary via the portal blood system.  The anterior pituitary then produces ACTH which stimulates the adrenal gland to produce glucocorticoids.  Glucocorticoids and ACTH send negative feedback to the hypothalamus.
  56. Why do you need to decrease exogenous corticosteroids slowly?
    Negative feedback of exogenous corticosteroids on the hypothalamus decreases the amount of endogenous glucocorticoids produced.  This suppression of ACTH causes atrophy of the adrenal gland.  Therefore suddenly stopping treatment can lead to a life threatening crisis.
  57. What are the different classes of drugs used to treat heart failure?
    Sympathomimetics, diuretics, vasodilators, inodilators, angiotensin II inhibitors
  58. What is the mechanism of action of dopbutamine?
    It is a synthetic B1 agonist.  It has potent positive inotropic effects.
  59. What is the mechanism of action of furosemide?
    Secreted into the PCT, acts in the thick ascending loop of henle to inhibit Na+/K+/2Cl- carrier in the lumenal membrane.  Ions and water are lost in urine.  Also induces renal PG synthesis.
  60. What is the mechanism of action of thiazides?
    Secreted into the PCT and act in the DCT, blocks Na+/Cl- reabsorption causing loss of electrolytes and water in urine.
  61. What is the mechanism of action of Amiloride?
    Acts on the CT to block the lumenal Na+ channel
  62. What is the mechanism of action of Spironolactone?
    Competitive aldosterone antagonist
  63. What type of diuretics are amiloride and spironolactone?
    Potassium sparing diuretics
  64. What is the mechanism of action of calcium channel blockers?
    Block L-type calcium channels
  65. What is the mechanism of action of alpha1 adrenoreceptor antagonists?
    Non-selective alpha1 antagonist
  66. What is the mechanism of action of nitrovasodilators (nitrates)?
    Nitrates act as donors of NO and mimic the NO pathway
  67. What is the mechanism of action of ACE inhibitors?
    Block the ACE active site to stop cleavage of angiotensin I into angiotensin II
  68. What is the mechanism of action of telmisartan?
    Competitive antagonist of the AT1 receptor
  69. What is the mechanism of action of inodilators?
    • Cardiac muscles: Bagonists stimulate adenylate cyclase and PDE III inhibitors prevent breakdown of cAMP, which both increase cAMP, calcium and contraction
    • Vascular smooth muscle: inhibitory effect on myosin kinase which decreases contraction and results in vasodilation
  70. What is the mechanism of action of bipyridine compounds (inodilator)?
    PDE III inhibitors
  71. What is the mechanism of action of pimobedan?
    Calcium sensitiser and PDE III inhibitor
  72. What is the mechanism of action of Class I anti-arhythmic drugs?
    Blocks Na+ channel
  73. What is the mechanism of action of Class II anti-arhythmic drugs?
    Beta blockers (antagonise beta receptors)
  74. What is the mechanism of action of Class III anti-arhythmic drugs?
    Block outward K+ channels
  75. What is the mechanism of action of Class IV anti-arhythmic drugs?
    Blocks Ca2+ channels
  76. What is the mechanism of action of cardiac glycosides e.g. digoxin?
    Increase parasympathetic activity and decrease sinus rate
  77. With regards to bradyarrhythmias, what is the mechanism of action of muscarinic antagonists?
    Antagonism of muscarinic ACh receptors
  78. With regards to bradyarrhythmias, what is the mechanism of action of b-agonists?
    Stimulate B-adrenergic receptors
  79. With regards to bradyarrhythmias, what is the mechanism of action of methyxanthines?
    Mild PDE inhibition and enhanced sympathetic drive
  80. What is the mechanism of action of vinca alkaloids?  What stage of the cell cycle do they act on?
    • Inhibit the mitotic spindle and prevent chromosomes being pulled apart in cell division
    • M phase
  81. What is the mechanism of action of antimetabolites?  What stage of the cell cycle do they act on?
    • They are analogues of DNA nucleotides that interfere with DNA synthesis 
    • S phase
  82. What is the mechanism of action of alkylating agents?
    They insert alkyl groups into DNA forming covalent bonds that cause inter/intrastrand cross linking. This inhibits RNA/protein synthesis, replication and transcription.
  83. What is a side effect of cyclophasphamide (example of alkylating agent)?
    Haemorrhagic cystitis
  84. What is the mechanism of action of Anti-tumour antibiotics?
    Intercalate in DNA preventing RNA/protein synthesis, inhibit topomerase II and produce free radicals.
  85. What is a side effect of doxyrubicin (example of anti-tumour antibiotic)?
    Cardiotoxicity
  86. What is the mechanism of action of cisplatin?
    It is a platinum compound that has a similar mechanism of action as alkylating agents i.e. inter strand cross linking
  87. What drug is more commonly used now than cisplatin?  Why?
    Carboplatin - it is less nephrotoxic
  88. What is the mechanism of action of L-asparginase?
    Depletes cells of aspargine by breaking it down into aspartic acid and ammonia.
  89. Why is L-asparginase selective for tumour cells?
    As normal cells can synthesise their own aspargine but tumour cells cannot
  90. What effect does an a) high b) low dose of glucocorticoids have for cancer treatment?
    • a) Inhibits lymphocyte proliferation
    • b) Reduces inflammation and stimulates appetite
  91. What glycoprotein is responsible for multi drug resistance in cancer treatment?
    p170

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