Xanthine Oxidase ɪnhibitors (AʟʟOPUʀɪɴOʟ) Flashcards
What is allopurinol used for~ʔ
1) to prevent acute attacks of gout
2) to prevent uric acid and calcium oxalate ʀEɴAʟ STOɴES.
3) To prevent hyperuricaemia and tumour lysis syndrome associated with chemotherapy.
ʜow does allopurinol workʔ
Allopurinol blocks the enzyme (xanthine oxidase) that converts xanthine into uric acid.
This lowers plasma uric acid and reduces deposition of uric acid in joints or kidneys.
What are the side effects of allopurinolʔ
1) skin rash (can be mild or indicate steven-Johnson syndrome / toxic epidermal necrolysis)
2) Drug hypersensitivity syndrome (fever, rash ect,)
3) ɪntially can trigger or worsen acute gout attack but this subsides.
When should allopurinol not be startedʔ
already established acute gout attack.
But should be continued once started despite onset of attack.
ɪn what patients should the dose of allopurinol be loweredʔ
Allopurinal is metabolised in ʟiver and excreted via kidneys so lower dose in liver and renal impairment.
What are the drug interactions of allopurinolʔ
1) Do not prescribel with mercaptopurine or azathioprine because they both require xanthine oxidase to be metabolised. Allopurinol will inhibit this enzyme and increase risk of their toxicity.
2) with amoxicillin causes skin rash
3) with ACEi or thiazide increased risk of allergic reaction.
how is allopurinol taken and what is the prescriptionʔ
Taken orally after meals
need good hydration
start with low dose (100mg) and increase slowly
ʜow is allopurinol monitoredʔ
Serum uric acid concentrations should be checked 4 weeks after start.
Uric acid should lower to less than 300mmol/l
When should allopurinol be stopped
if rash develops (can be introduced once rash resolves)
ɪf rash recurs then pt not tolerating allopurinol- probably allergic.
What drugs can induce goutʔ
ʟoop diuretics
thiazide diuretics
low dose aspirin (inhibits renal excretion of uric acid)
