Glucarpidase

How it works

It is a carboxypeptidase that cleaves circulating methotrexate into inactive metabolites, providing an alternative, kidney-independent route of elimination.

Prescribing in practice

• Continue folinic acid rescue and hydration, but do not give folinic acid in close proximity to glucarpidase, as the enzyme also degrades folinic acid — refer to the SPC for timing.
• Reserve for confirmed toxic methotrexate levels with impaired renal clearance, in consultation with toxicology and the treating oncology team.
• Be aware that standard methotrexate immunoassays may overestimate levels after administration owing to interference from the metabolite.

Monitoring

Monitor methotrexate levels, renal function and full blood count, interpreting post-dose methotrexate assays with caution.

Counselling the patient

• Explain that this enzyme rapidly clears a chemotherapy drug that the kidneys are struggling to remove.
• Tell the team to coordinate the timing of folinic acid around the enzyme dose.
• Advise the patient that close blood monitoring will continue afterwards.

Evidence & guidelines

Glucarpidase is used to reduce toxic plasma methotrexate concentrations in patients with delayed clearance and renal dysfunction, alongside continued folinic acid rescue and hydration.