Nursing care
Antigout Agents: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Antigout agents fall into two groups with opposite jobs: allopurinol lowers uric acid to prevent attacks, while colchicine treats an attack already underway. Starting allopurinol during an acute flare can worsen it by mobilising urate crystals, so timing is the first thing to check before giving either drug.
Mechanism, simply
Allopurinol blocks xanthine oxidase, the enzyme that converts purines into uric acid. Less uric acid is made, so serum urate falls over weeks and crystals stop forming in joints. It does nothing for pain already present because it does not touch inflammation, only production.
Colchicine works differently. It binds tubulin and disrupts neutrophil migration into the joint, cutting off the inflammatory response that urate crystals trigger. It does not lower uric acid at all. One drug prevents the fuel supply; the other shuts down the fire once it has started. Confusing the two, or their timing, is the single most common error on this topic.
Indications you will see on the ward
Allopurinol is prescribed for chronic gout prophylaxis, tumour lysis syndrome prevention before chemotherapy, and recurrent urate kidney stones. It is a long-term, daily maintenance drug started once a patient is between flares, not during one.
Colchicine appears for acute gout flares, often at the first twinge of pain, and at low dose for flare prophylaxis when allopurinol therapy is first started, because urate lowering can itself trigger a flare in the initial months. You will also see colchicine used off-label for pericarditis. On a med-surg floor, the patient newly started on allopurinol who also has a colchicine or NSAID prescription for the first few months is not a prescribing error, it is standard practice.
Assessment before administration
Before allopurinol, check renal function. Dose is renally adjusted, and reduced clearance raises the risk of toxicity, including a rare but severe hypersensitivity syndrome. Ask about HLA-B*5801 status if it has been tested, since carriers, more common in patients of Southeast Asian or African descent, are at higher risk of severe skin reactions and may need it avoided or dose-titrated carefully.
Before colchicine, check renal and hepatic function, since both slow clearance and narrow an already tight therapeutic window. Ask what else the patient takes: colchicine has a short list of interactions that turn a normal dose into a toxic one. Confirm the joint symptoms are consistent with gout rather than septic arthritis, since colchicine treats inflammation but will mask nothing if the diagnosis is wrong and the source is infective.
Toxicity and the antidote
Colchicine toxicity is dose-related and has no specific antidote; management is supportive, including GI decontamination if caught early and haemodynamic support, because overdose can progress to multi-organ failure and bone marrow suppression. Early signs are gastrointestinal: nausea, vomiting, and diarrhoea, often before any other toxicity appears, so new GI symptoms in a patient on colchicine are not routine and should be reported.
Allopurinol's toxicity picture is different. Watch for skin reactions ranging from a mild rash to Stevens-Johnson syndrome or toxic epidermal necrolysis, and stop the drug immediately if a rash appears rather than waiting to see if it worsens. There is no antidote for allopurinol hypersensitivity syndrome either; treatment is drug withdrawal plus supportive care, and in severe cases, corticosteroids.
Interactions that matter
Allopurinol raises levels of azathioprine and 6-mercaptopurine dramatically, because it blocks the same enzyme pathway that clears them; the combination needs major dose reduction or avoidance. It also increases the effect of warfarin, so INR needs closer monitoring when the two are started together.
Colchicine is metabolised by CYP3A4 and cleared partly by P-glycoprotein, so strong inhibitors of either, including clarithromycin, some antifungals, and certain calcium channel blockers, can push colchicine to toxic levels even at a normal prescribed dose. This interaction is a recognised cause of fatal colchicine toxicity and is worth flagging on medication reconciliation, particularly in older adults on multiple prescriptions.
What the patient must be told
Tell the patient starting allopurinol that it will not relieve a current flare and may even provoke one in the first weeks, so a short course of colchicine or an NSAID is normal alongside it, not a sign something has gone wrong. Adequate fluid intake helps prevent urate stone formation while the drug takes effect.
Tell the patient given colchicine for a flare to take it exactly as prescribed and to stop and call their team if diarrhoea, vomiting, or unusual bruising develops, since these can be early toxicity rather than routine side effects. Both drugs need alcohol intake discussed, since alcohol raises urate levels and can trigger the very flares allopurinol is meant to prevent.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Why does starting allopurinol during an acute gout attack make it worse?
Allopurinol changes serum urate levels as it starts working, and that shift can mobilise crystals from tissue deposits into the joint space, triggering or worsening inflammation. It is started once the current flare has settled, then continued long-term with prophylactic colchicine or an NSAID cover for the first few months.
Can colchicine and allopurinol be given together?
Yes, and this is standard practice when allopurinol is first started, since low-dose colchicine for several months reduces the risk of a flare triggered by the changing urate level. They are not interchangeable, and one is not a substitute for the other.
What is the first sign of colchicine toxicity to watch for?
Gastrointestinal symptoms, particularly diarrhoea, nausea, and vomiting, typically appear before other signs of toxicity and can precede more serious effects like bone marrow suppression. Any new GI symptoms in a patient on colchicine warrant prompt reporting rather than being treated as routine.
Does allopurinol treat gout pain?
No. Allopurinol lowers uric acid production to prevent future attacks; it has no anti-inflammatory or analgesic effect on a joint that is already flaring. Pain during a flare is managed with colchicine, an NSAID, or a corticosteroid depending on the patient.
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