Renal (kidney) involvement is common, occurring in 30-70 % of patients. Kidney disease is usually noted after the onset of systemic symptoms. More marked findings may also occur including nephrotic syndrome, a situation characterized by abnormal excretion of proteins and lipids in urine, swelling (edema), low level of albumin in blood and hyperlipidemia. High blood pressure (hypertension) and acute kidney failure may also be seen. Worsening of the kidney symptoms and biopsy-confirmed worsening of the kidney lesions may be observed in patients with repeated attacks of rash or hematuria (blood in the urine).
Use caution when administering high-dose methotrexate to patients receiving proton pump inhibitor (PPI) therapy. Case reports and published population pharmacokinetic studies suggest that concomitant use of some PPIs, such as omeprazole, esomeprazole, and pantoprazole, with methotrexate (primarily at high doses), may elevate and prolong serum levels of methotrexate and/or its metabolite hydroxymethotrexate, possibly leading to methotrexate toxicities. In two of these cases, delayed methotrexate elimination was observed when high-dose methotrexate was co-administered with PPIs, but was not observed when methotrexate was co-administered with ranitidine. However, no formal drug interaction studies of methotrexate with ranitidine have been conducted.