Allopurinol

Question 1

Allopurinol - indications

Answer 1

1. To prevent recurrent attacks of gout.
2. To prevent uric acid and calcium oxalate renal stones.
3. To prevent hyperuricaemia and tumour lysis syndrome associated with chemotherapy.

Question 2

Allopurinol - MOA

Answer 2

Xanthine oxidase metabolises xanthine (produced from purines) to uric acid.

Allopurinol is a xanthine oxidase inhibitor.

Inhibition of xanthine oxidase lowers plasma uric acid concentrations and reduces precipitation of uric acid in the joints or kidneys

Question 3

Allopurinol - Adverse effects

Answer 3

Allopurinol is generally well tolerated.

The most common side effect is a SKIN RASH, which may be mild or may indicate a more serious hypersensitivity reaction such as Stevens–Johnson syndrome or toxic epidermal necrolysis - allopurinol treatment should be stopped if a rash develops.

Allopurinol hypersensitivity syndrome is a rare, life-threatening reaction to allopurinol that can include fever and lymphadenopathy

Question 4

What can happen when a patient first starts taking Allopurinol for prevention treatment fo their gout?

Answer 4

Starting allopurinol can trigger or worsen an acute attack of gout

The risk of triggering an attack may be reduced by co-prescription of an NSAID or colchicine (for atleast 1 month after serum uric acid levels normalise) in the initiation phase

Question 5

Should Allopurinol be started during an acute attack of gout?

Answer 5

Allopurinol should not be started during acute attacks of gout BUT can be continued if a patient is already established on it, to avoid sudden fluctuations in serum uric acid levels.

Question 6

Allopurinol - contraindications

Answer 6

• should not be STARTED during acute attcks of gout
• recurrent skin rash
• severe hypersensitivity

Question 7

Allopurinol - cautions

Answer 7

The dose should therefore be reduced in patients with:

• severe renal impairment
• hepatic impairment

WHY?
Allopurinol is metabolised in the liver and excreted by the kidney.

Question 8

Allopurinol - Interactions

Answer 8

• azathioprine (increases risk of toxicity)
• ACE inhibitors or thiazides (increase risk of hypersensitivity reactions)
• amoxicillin (increase risk of skin rash)

Question 9

Allopurinol - administration

• how many to take
• how to take it

Answer 9

Take one tablet a day w/food and a glass of water

Allopurinol should be taken after meals and patients should be encouraged to maintain good hydration with fluid intake of 2–3 litres daily.

Question 10

Allopurinol - patient explanation of what this medication does (gout)

Answer 10

Advise patients that the purpose of treatment is to reduce attacks of gout

Question 11

Allopurinol - monitoring

Answer 11

Serum uric acid concentrations should be checked 4 weeks after initiating allopurinol or after a change in dose.

You should aim to lower uric acid concentrations to <300 µmol/L where possible, by increasing the dose of allopurinol as needed.