NSAIDS Flashcards
What activity does NSAIDS have?
Think the 3As:
Antipyretic (reduce fever)
Analgesic (pain relief)
At higher doses anti-inflammatory effects
How do NSAIDs work?
NSAIDs work by inhibiting the COX enzymes (COX-1 and COX-2). COX (cyclooxygenase) is a type of enzyme that acts in the phospholipid/arachidonic acid pathway initiated as a responsible to inflammation that faciliates the production of prostanoids, thromboxane, prostacyclin from arachidonic acid specifically.
Describe in full the arachidonic acid pathway.
When endotoxins are released by (gram negative) bacterium this causes damage to cell membranes which activates phospholipase A2 an enzyme which degrades phospholipids present within the cell membrane converting them to arachidonic acid. Arachidonic acid is then acted upon by two enzymes lipo-oxygenases which produces leukotrienes and cyclo-oxygenases. When either COX-1 or COX-2 acts on arachidonic acid converting it to two short-lived intermediates, PGG2 and PGH2. PGH2 is then metabolized to a variety of prostaglandins and related compounds collectively referred to as prostanoids; PGD2, PGE2, PGF2α, PGI2 and TXA2 (thromboxane).
How do the COX enzymes convert arachidonic acid to the prostanoids?
They combine arachidonic acid (and some other unsaturated fatty acid) substrates with molecular oxygen to form unstable intermediates, cyclic endoperoxides, which can subsequently be transformed by other enzymes to different prostanoids.
What are the role of lipooxygenases?
Catalyse the oxygenation of polyunsaturated fatty acids such as arachidonic acid and linoleic acid to produce leukotrienes, lipoxins and other compounds
What leukotrienes are produced from lipo-oxygenases specifically in the arachidonic acid pathway?
Leukotriene B4, C4, D4 and E4
What is the crucial difference between COX-1 and COX-2?
COX-1 is a homeostatic regulator (responsible for inducing vascular responses and gastric acid secretion) and in most cells under normal physiological conditions. COX-2 however is only produced in response to inflammation and therefore a stronger drug target.
Aside for the production of COX-2 in inflammation, what cell types is it present in under normal physiological conditions?
CNS and renal tissue
Which prostaglandins are produced by COX-1 and which by COX-2?
Whilst COX-1 and COX-2 have the same products (prostacyclin, prostaglandins and thromboxane) but they have different therapeutic effects depending on which enzyme and under what conditions they have been produced.
For example prostaglandins produced by COX-2 in response to inflammation causes pain, fever and inflammation but prostaglandins produced by COX-1 under normal physiological conditions has an effect on the GI tract, thrombocyte and kidney function and blood-flow.
What prostaglandins are produced specifically from the COX/arachidonic acid pathway?
Prostaglandin D2, E2, F2a, I2 alongside prostacylin and thromboxane (TXA2)
Would you want an NSAID to be COX-1 or COX-2 selective?
COX-2 selective as it is this enzyme specifically that is present in response to inflammation causing fever, pain and other therapeutic effects a patient would experience. Inhibition of COX-1 leads to a variety of side effects (GI).
How are the different types of NSAIDs classified?
Dependent on how selective they are for COX-1 or COX-2.
Standard NSAIDs- non-selective for COX-1 or COX-2
COXIBS- COX-2 selective (still a slight affinity to COX-1)
What are some examples of standard NSAIDS?
Ibuprofen
Aspirin
Indometacin
Mefenamic acid
Naproxen
Non-selective NSAIDS but a preference for COX-2:
Diclofenac
Etodolac
Meloxicam
Nabumetone
What are some examples of licensed COXIBS?
Celecoxib and Etoricoxib
What prostanoid dominates in inflammation?
Prostaglandin E2 but I2 also has an effect
What are the functions of prostaglandin D2?
Vasodilation
Inhibits platelet aggregation
Relaxes GI and uterine muscle
Modification of release of hypothylamus and pituitary hormones
Chemo-attractants of leukocytes
Bronchoconstrictor
What are the functions of prostaglandin F2a?
Uterine contraction
What are the functions of prostaglandin I2?
Vasodilation
Inhibits platelet aggregation
Stimulates renin release
Natriuresis through its effects of tubular reabsorption of sodium
What are the functions of thromoxane A2?
Vasoconstriction
Platelet aggregation, bronchoconstriction
What are the functions of prostaglandin E2 at EP1 receptors?
Contraction of the bronchial and gastro-intestinal smooth muscle
What are the functions of prostaglandin E2 at EP2 and EP4 receptors?
Bronchodilation
Vasodilation
Stimulation of intestinal fluid secretion
What are the functions of prostaglandin E2 at EP3 receptors?
Contraction of the intestinal smooth muscle
Inhibits gastric acid secretion
How do the production of the prostanoids differ in acute and chronic inflammation?
In acute inflammation prostaglandin E2 and I2 are generated by local tissues and blood vessels and prostaglandin D2 is released by mast cells.
In chronic inflammation monocytes/macrophages release prostaglandin E2 and TXA2 together. It is a ying yang effect in which prostanoids stimulate some responses and decrease others.
Which two drugs which can be catorgrised as NSAIDs have a different pharmacological actions to the others?
Aspirin and paracetamol
Explain the anti-inflammatory action of NSAIDs.
Anti-inflammatory action is due to a decrease in prostaglandin E2 and prostacylin specifically which reduces vasodilation and oedema. However crucially NSAIDs do not have an effect on the accumulation of anti-inflammatory cells.
Explain the analgesic action of NSAIDs.
This is due to the reduced synthesis of prostaglandins meaning there is less sensitisation of nociceptive nerve ending specific to inflammatory mediators like bradykinin.
Reduced vasodilatory effect leading to relief of headache.
Explain the anti-pyretic effect of NSAIDs.
IL-1 releases prostaglandins into the CNS which elevates the hypothalamic set point for temperature control hence causing fever, NSAIDs prevent this.
What are the four indications of NSAIDs?
Antithrombotic
Analgesia
Anti-inflammatory
Anti-pyretic
For each of the four indication of NSAIDs give example of the most appropriate drug to use.
Anti-thrombotic: only aspirin for risk of arterial thrombosis, other ones increase the risk of thrombosis
Analgesia:
Short-term - ibuprofen, paracetamol
Long-term- pivorixam, naproxen
Anti-inflammatory: ibuprofen, naproxen
Anti-pyretic: paracetamol
Describe the activity of paracetamol in application to ‘typical’ NSAID activity.
Analgesic and anti-pyretic activity but no significant anti-inflammatory activity
What effect does paracetamol have on COX enzymes?
Although paracetamol is still a COX inhibitor this activity is restricted to the CNS COX enzymes.
What are some of the OTC interventions that have been made/can be made to prevent paracetamol overdosing.
Check for duplicate prescribing (appropriate counselling/restriction on a patient buying two compund preparations that contain paracetamol)
Limited packet size at 32, can sell up to 100 under pharmacist supervision