Numerous drug interactions with methotrexate have been identified, which can lead to serious life-threatening effects. Up to 90% of methotrexate is excreted unchanged in the urine with primary excretion dependent on organic anion transport in the renal proximal tubule. The two pathways responsible for methotrexate secretion are organic anion transport 1 and primarily organic anion transport 3. Penicillins undergo tubular secretion via organic anion transport, and cephalosporins are believed to also possess a similar risk when administered with methotrexate; however, there are no human studies observing this interaction with cephalosporins and methotrexate. Ceftriaxone undergoes biliary clearance and has low affinity for the same organic anion transports as methotrexate; therefore, ceftriaxone has a low potential to interact with methotrexate. Cefepime is primarily secreted by organic cation transport N2, and also has a low potential to interact with methotrexate. This case report describes the pharmacokinetic effect of concomitant beta-lactam therapy in a patient receiving high-dose methotrexate.
Background: Idiopathic membranous nephropathy (IMN) remains the leading cause of adult nephrotic syndrome. Immunosuppressive therapy with cyclophosphamide (CTX) is often successful in reducing proteinuria, but its use is associated with severe side effects. Tacrolimus (TAC) is effective in achieving complete remission (CR) in patients with IMN. However, whether it is as effective as CTX in inducing and maintaining complete or partial remission in these patients is unknown. This trial aims to test TAC monotherapy for its non-inferiority to CTX in inducing longterm remission of proteinuria. Methods: Patients with biopsy-proven IMN with nephrotic syndrome will be randomized into a 12-month treatment period with oral TAC of 0.05-0.1 mg/kg/day for 6 months or with CTX + glucocorticoid. The efficacy of the treatment will be assessed by the remission status (based on changes in proteinuria) and relapse rate. Discussion: This study will test whether treatment with TAC monotherapy is superior to CTX with glucocorticoid in inducing long-term remission of proteinuria in patients with adult IMN. The role of serum anti-PLA2R antibodies in the early assessment of the response to therapy using different therapeutic regimens will also be clarified. Trial registration: ClinicalTrials.gov ChiCTR1800016140. Registered 12 June 2017. http://www.chictr.org.cn.
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