tacrolimus and ibuprofen

The interaction is primarily pharmacodynamic. Tacrolimus causes afferent arteriolar vasoconstriction in the kidney, reducing renal blood flow. Ibuprofen and other nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis, which normally dilates the afferent arteriole. Combined use leads to an additive reduction in renal perfusion and glomerular filtration, increasing the risk of ischaemic injury. Additionally, in some cases, ibuprofen may modestly increase tacrolimus trough levels, possibly through competitive inhibition of hepatic metabolism, but this is less consistent.

Patients receiving both drugs are at an increased risk of acute kidney injury, which may manifest as rising serum creatinine, reduced urine output, or fluid overload. This can be particularly dangerous in transplant recipients where stable renal function is critical for graft survival. The interaction may also lead to electrolyte imbalances such as hyperkalaemia. In some cases, the renal impairment is reversible, but it can be serious enough to require hospitalisation or dialysis.

Avoid co-prescription where possible. Consider alternative analgesia such as paracetamol. If the combination is necessary, ensure adequate patient hydration and closely monitor renal function (serum creatinine, BUN, urine output) at baseline, then at least weekly for the first month or more frequently if renal dysfunction is evident. Also monitor tacrolimus trough levels as renal function changes can affect its clearance; adjust tacrolimus dose as needed. Advise patients to seek medical attention if they note decreased urine output, swelling, or nausea.

This interaction is well documented in transplant literature and is included in major drug interaction databases. Evidence is based on clinical studies, case reports, and post-marketing surveillance, showing an increased risk of nephrotoxicity with combined use. However, specific pharmacokinetic data for ibuprofen in this context are limited.