Makindo Medical Notes

Always check the BNF link here or equivalent for prescribing advice

• 🧪 Probenecid is a uricosuric drug that has historically also been used to boost concentrations of other drugs (e.g. penicillin).
• 📌 Occasionally misused to mask drugs in athletes’ urine screens.

⚙️ Actions

• 🚫 Blocks transport of organic acids across renal tubular membranes, reducing their excretion.
• 💧 Actively excreted in the proximal convoluted tubule, reabsorbed in the distal tubule.
• ⬇️ Reduces uric acid reabsorption and ⬆️ increases renal excretion of urate.

🎯 Indications

• 🦶 Gout / Hyperuricaemia: increases uric acid clearance.
• 💉 Historically used to prolong penicillin levels in plasma.
• 🚫 Misuse in sport: used to mask drug presence in urine analysis (banned in competitive athletics).

🔄 Interactions

• ⬆️ Increases blood concentrations of oseltamivir and some antivirals.
• 🚫 Aspirin reduces the uricosuric effect and should be avoided.
• 💊 Can affect levels of some antibiotics and antivirals (consult BNF for full list).

⚠️ Side Effects

• 🤢 Dyspepsia, GI upset.
• 🌸 Allergic reactions (rash, pruritus).
• 🧪 Rare: nephrolithiasis, anaemia, or uric acid kidney stones with long-term use.

📊 Dose

• 💊 Start: Probenecid 250 mg BD PO.
• ⬆️ Titrate according to serum urate levels.
• 📌 Usual maximum dose: 2 g/day.
• ⚠️ Ensure good hydration to reduce kidney stone risk.

📚 Teaching Points

• 🔑 Not first-line for gout — now largely replaced by allopurinol and febuxostat.
• 💧 Uricosuric effect requires good renal function; avoid in renal impairment.
• 🚫 Contraindicated in patients with history of uric acid kidney stones.
• ⚖️ Interesting historically: used in WWII to prolong scarce penicillin supplies.