Allopurinol

Which pharmacological group of anti-gout agents does allopurinol belong to?

Allopurinol belongs to the pharmacological group of urate-lowering agents, which are xanthine oxidase inhibitors. The main goal of using drugs from this group is to reduce plasma uric acid levels by suppressing its synthesis. This is necessary to prevent new disease attacks and tophus formation. Allopurinol is the first-line drug for baseline (urate-lowering) therapy of gout.

What are the main adverse effects characteristic of allopurinol?

Allopurinol is characterized by a wide spectrum of adverse effects affecting various systems:

• Paradoxical flare — the risk of developing an acute gout attack in the first weeks of therapy.
• Allergic reactions — dermatitis, skin pruritus, urticaria, erythema multiforme exudativum (Stevens-Johnson syndrome), and toxic epidermal necrolysis (Lyell syndrome).
• Blood system — agranulocytosis, anemia, thrombocytopenia, eosinophilia, leukopenia.
• Urinary system — acute renal failure, interstitial nephritis.
• Nervous system — somnolence, headache, dizziness, asthenia.
• Musculoskeletal system — myopathy, myalgia, arthralgia.
• Gastrointestinal tract — dyspepsia (diarrhea).

Is it advisable to use allopurinol to relieve an acute gout attack?

It is not advisable to use allopurinol to relieve an acute gout attack. The drug is not used for direct treatment and pain relief in the acute phase of the disease; an acute gout attack is listed among the contraindications for allopurinol. Allopurinol is used as baseline urate-including therapy for the prevention of gout attacks, including during the interictal period. During an acute attack, changes in the dosage of urate-lowering drugs should be avoided, as abrupt fluctuations in urate levels can aggravate the course of the attack.

With which immunosuppressants and antineoplastic drugs does allopurinol clinically significantly interact?

Allopurinol engages in clinically significant interactions with the following drugs:

• Mercaptopurine — an antineoplastic agent. Allopurinol inhibits xanthine oxidase, slowing down the metabolism of mercaptopurine. This leads to a sharp increase in its toxicity (bone marrow suppression), so the dose of mercaptopurine must be reduced by 75%.
• Azathioprine (Azathioprine) — an immunosuppressant. Allopurinol inhibits the metabolism of its active derivatives, which causes an enhancement and prolongation of azathioprine's action with a high risk of toxicity.