Allopurinol

Question 1

Mechanism of action ?

Answer 1

Xanthine oxydase inhibitor. This enzyme metablises Xanthine to uric acid.

Question 2

Indications ?

Answer 2

• Prevent acute attacks of Gout
• Prevent formation of uric acid and calcium oxalate renal stones.
• Before starting a chemotherapy to prevent hyperuricemia and tumor lysis syndrome.

Question 3

Tumor lysis syndrome/Syndrome de lyse tumoral?

Answer 3

Range of metabolic abnormalities resulting from a large number of cancer cells destroyed with their contents delivered into the bloodstream.

Question 4

Important AE ?

Answer 4

Generally well tolerated, but a skin rash can develop and be : either a begnin sign shortly disappearing after cutting off the drug, or : a hypersensitivity reaction evoking Stevens Johnson syndrome or toxic epidermal necrolysis.
Allopurinol can trigger or worsen (an) gout attack.

Question 5

Important cautions ?

Answer 5

Allopurinol should not be started during acute gout attacks, but must be continued if a patient is already established on it to avoid fluctuations in uric acid serum levels.
It is metabolised by liver and excreted by kidneys. (reduced doses in cases of impairments)

Question 6

Important interactions ?

Answer 6

Mercaptopurine &its pro-dryg Azathioprine require Xanthine oxydase for metabolism.
Amoxicillin can increase the risk of skin rash.
ACE inhibitors and Thiazides can increase the risk of hypersensitivity reactions.

Question 7

Mercaptopurine ?

Answer 7

Antimetabolite analogue au purine, traitant specifiquement : Leucémie aigue lymphoblastique, Leucémie aiguë myéloblastique, leucémie myéloïde chronique et colite ulcerative. Generalement associé au Methotrexate.

Question 8

How is Allopurinol prescribed in Gout (starting a treatment) ?

Answer 8

Starting dose is usually low, at 100 mg per ex. and titrates up according to uricemia levels for maintenance 200-600mg daily in 1-2 divided doses.
NSAIDs or Colchicine should be co-administered when starting treatment with Allopurinol and maintained for up to a month to avoid triggered gout attacks.

Question 9

When should Allopurinol be taken ?

Answer 9

After meals with good hydration throughout the treatment.

Question 10

Normal levels of uric acid ?

Answer 10

240-360 umol/l pour un homme
180-300 umol pour une femme
150-240 umol/l pour un enfant

Question 11

Monitoring ?

Answer 11

4 weeks after initiating treatment/at changing dosage.

For mild skin rashes, it can be reintroduced cautiously.

Question 12

Gout can be triggered by drugs, some in cause ?

Answer 12

Loop diuretics and Thiazide (increase levels of uric acid)

Low-dose Aspirin inhibits renal excretion of uric acid.

Question 13

Generique de l’Allopurinol ?

Answer 13

ZYLORIC Cp à 100 mg