NSAIDs Flashcards
What is Arachadonic acid derived from?
Linoleic acid - vegetable oils.
It is the converted hepatic ally to arachidonic acid and incorporated into phospholipids.
Where is arachidonic found?
Found throughout the body - particularly in the muscle, brain and liver.
What is the rate limiting step in eicosanoid generation?
Release from phospholipids by phospholipase A2.
Describe Eicosanoid synthesis
Phospholipids are converted into arachidonic acid by phospholipase A2.
Arachidonic acid then gets converted into Prostaglandin H2 via the cyclooxygenase pathways (where COX1 and COX2 work).
Prostaglandin H2 then gets converted into various prostanoids which act in different ways depends on where in the body they are.
The prostanoids all have a short half life so are under fine control.
What are prostanoids used for?
They have various different functions depending on where in the body they are produce and the type.
PGE2 - stomach for GI mucosal protection, uterine contraction and brain.
PGE2, PGF2a, PGD2 - pain, pyrexia and inflammation
What is the difference between COX1- and COX2?
They are the two functional isoforms of cycooxygenase enzymes.
COX1 - constitutively active across most tissues
COX2 - Inducible (mostly) typically in active / inflamed tissues.
Homeostatic functions of COX-1
GI protection (acid and mucus)
Platelet aggregation
Vascular resistance
Renal blood flow
Homeostatic functions of COX-2
Renal homeostasis
Tissue repair and healing
Reproduction (uterine contractions)
Inhibition of platelet aggregation
Pathological functions of COX-1
Chronic inflammation
Chronic pain
Raised blood pressure
Pathological function of COX-2
Chronic inflammation Chronic pain Fever Blood vessel permeability Tumour cell growth
How can prostanoid action be enhanced?
Local autacoids including bradykinin and histamine
TXA2 and PGI2 have apposing vascular effects. Why is this significant?
Because it is important to maintain a fine balance between them for haemodynamic and thrombogenic control.
Imbalance plays a significant role in hypertension, MI and stroke.
Why might a diet rich in fish oils be protective?
EPA and DHA concession of TXA3 and PGE2 - balance shifted towards prostacyclin activity which could lead to a lower incidence of CVD.
What is the single MOA of NSAIDs?
Inhibition of COX enzymes causing a decrease in prostanoid (prostaglandins, prostacyclin and thromboxane) synthesis.
This is good or bad depending on what actions (homeostatic or pathogenic) actions are being targeted.
How does aspirin work at a high die?
Original NSAID
Aspirin irreversibly inhibits COX - why issue with platelet aggregation.
How do NSAIDs have an analgesic effect?
Local peripheral action at site of pain - greater efficacy if inflamed.
Central component associated with decrease PGE2 synthesis in the dorsal horn causing decrease neurotransmitter release resulting in decreased excitability of neurones in pain relay.
Efficacious after first dose but full analgesia after several days of dosing.