gout is accumulation of uric acid in joints , due to high uric acid level in the body
uric acid is the end product of purine , purine result from dna breakdown after cell death ( xanthin oxidase the enzyme responsible for breakdown of purine to uric acid )
uric acid is strong antioxidant , has good rule in immunity , like vit c (but body cant produce vit c )
causes of high uric acid in body
1-eating meat food or any food with high purine
2- tumor lysis syndrome that occur in pt with malignancy
3- the most important and most common 90% , defect in excretion , in kidney , proximal tubule responsible for excretion of uric acid and any other acid in the body , also defect in reabsorption in kidney
note: any drug like aspirin salicylic acid compete with uric acid on kidney excretion and any drug contain acid will increase uric acid in the body
patient will come with joints pain and tingling , stings , also tip toe pain and stings is increase suspicion of gout
send him uric acid test , if >7 (3-7 normal range) this will confirm the diagnosis
whats gout treatment :
probenecid 500mg by 2 or 3 (minimum 1g by day to be effective in prevent reabsorption of uric acid)
mechanism : inhibit tubular reabsorption of urate , thus increasing urinary excretion of uric acid and decrease serum urate level
allopurinol (zyloric) 100mg or 300mg :
mechanism : inhibit xanthine oxidase , that enzyme convert hypoxanthine to xanthine which convert purine to uric acid
acute attack of gout :
patient with severe pain , due to inflammation in joint due to deposition of uric acid in joints
it is wrong to give allopurinol or probenecid in acute attack , it will increase the pain , because those drug reduce uric acid level in blood that will drive uric acid crystals from joint to blood , and during this process , macrophage will attack uric acid moving from joint (recognize him as foreign body ) and macrophage will burst and the enzymes inside macrophage like (interleukin and prostaglandin ) will release into joint , and will lead to severe inflammation and this will increase the pain
so in acute attack we should give anti-inflammatory drugs first
1-NSAID : cox enzyme inhibitors that enzyme responsible for prostaglandin formation ,
selective NSAID (act on cox2 only) like etrocoxib , celocoxib
non selective NSAID (act on cox1 , cox2) like ibuprofen (profen) , diclofenac (voltaren)
2-colchicine : inhibit mitosis of immunity cells like basophils and neutrophils
dose : first dose 0.6mg (one tablet ) , after 1hr , another tablet , and then after 12hr give tablet , then by 2
or 1.2mg (2 tablet ) first , then after 1hr another tablet (not exceeding 1.8mg per hr )