Bonus drugs - antibiotics, analgesics etc. Flashcards
how does N-acteylcysteine work as an antidote to paracetamol overdose?
in therapeutic doses, paracetamol is metabolised mainly by conjugation with glucuronic acid and sulfate, with a small amount converted to a hepatotoxic metabolite - normally quickly detoxifed by conjugation with glutathione.
in paracetamol overdose, the body’s supply of glutathione is overwhelmed, toxic produce begins to damage the liver.
acetylcysteine works by replenishing the body’s supply of glutathione to breakdown the paracetamol.
how does activated charcoal work as a poison antidote?
molecules are adsorbed onto the surface of the charcoal due to Van der Waals forces as they travel through gut - reduced absorption.
can also increase elimination of some poisons - multiple doses maintain a steep concentration gradient encouraging diffusion of the poison out of the circulation.
how does naloxone act as an opiate antidote?
binds to opioid receptors, acting as a competitive antagonist - naloxone will displace the opioid from the receptors, reversing its effects.
describe the mechanism of action of paracetamol
weak COX2 inhibitor - involved in prostaglandin metabolism.
in CNS, COX inhibition increases the pain threshold.
name some weak opioids and describe their mechanism of action
tramadol, codeine, dihydrocodeine.
metabolised in liver to produce small amounts of morphine - agonist of opioid mu-receptors, producing the analgesic effect.
name some strong opioids and describe their mechanism of action
morphine, oxycodone.
activation of mu-receptors in CNS - reduces neuronal excitability and pain transmission.
give some examples of NSAIDs and describe their mechanism of action
ibuprofen, naproxen, etoricoxib, diclofenac.
inhibit synthesis of prostaglandins from arachidonic acid by inhibiting COX.
what are the main side effects of NSAIDs?
GI ulcers/bleeding.
renal impairment.
name some systemic corticosteroids.
prednisolone, hydrocortisone, dexamethasone.
how do systemic corticosteroids work?
bind to cystolic glucocorticoid receptors, which translocate to the nucleus where they regulate gene expression.
up-regulate anti-inflammatory genes, down-regulate pro-inflammtory genes (e.g. cytokines, TNF-alpha).
what is the risk of withdrawing steroids suddenly?
Addisonian crisis with cardiovascular collapse.
describe how oestrogens and progesterones are used for contraception
they both exert negative feedback on LH and FSH release - used to suppress these hormones, and thus suppress ovulation.
give some indications of adrenaline
cardiac arrest.
immediate management of anaphylaxis.
describe the mechanism of action of adrenaline
potent agonist of alpha 1+2 and beta 1+2 adrenoreceptors - sympathetic effects:
vasoconstriction, increased HR, force and excitability, vasodilation of vessels supplying heart and muscles.
suppression of inflammatory mediator release from mast cells.
to what class of antibiotics do gentamicin and streptomycin belong?
aminoglycosides
name 2 aminoglycosides
gentamicin, streptomycin, amikacin
give 2 indications for use of aminoglycosides
severe infections, particulary due to Gram-ve anaerobes (incl. Pseudomonas).
severe sepsis.
pyelonephritis + complicated UTI.
biliary sepsis.
endocarditis.
describe the mechanism of action of aminoglycoside antibiotics
BACTERICIDAL.
bind irreversibly to bacterial ribosomes and inhibit protein synthesis.
list 2 antifungal drugs
nystatin, clotrimazole, fluconazole, ketoconazole.
how does nystatin work against fungi?
bind to ergosterol in fungal cell membranes, creating a polar pore which allows intracellular ions to leak out of the cell - kills/slows growth of fungi
how do azoles (ketoconazole, clotrimazole and fluconazole) work against fungi?
inhibit ergosterol synthesis, a component of cell membrane - so impair cell membrane synthesis, cell growth and replication.
give 2 examples of cephalosporin/carbapenem antibiotics
cephalosporins - cefuroxime, cefalexin, cefotaxime,
carbapenems - imipenem, meropenem, ertapenem
what is an indication for oral cephalosporins?
second + third line treatment options for UTI/resp tract infection