eGFR Cutoff for Starting Jinarc (Tolvaptan) in ADPKD
Tolvaptan should be initiated when eGFR is ≥25 mL/min/1.73 m² in patients with autosomal dominant polycystic kidney disease (ADPKD) who are at risk for rapid progression, and once started, it should be continued even as eGFR declines below this threshold unless dialysis is initiated or intolerance develops.
Initiation Threshold
The eGFR cutoff for starting tolvaptan (Jinarc/Samsca) in ADPKD is ≥25 mL/min/1.73 m² based on regulatory approval criteria and clinical trial inclusion parameters 1.
Patients must demonstrate evidence of rapid disease progression to justify initiation, which can be assessed through Mayo imaging classification (class 1C-1E), historical eGFR decline rate, or elevated urinary biomarkers such as β2-microglobulin and MCP-1 2.
Continuation Below Initiation Threshold
Once tolvaptan is started, continue it even if eGFR falls below 25 mL/min/1.73 m² until kidney replacement therapy is initiated or the patient develops intolerance 3, 4.
This continuation strategy mirrors the approach used with SGLT2 inhibitors in diabetic kidney disease, where ongoing nephroprotection justifies continuation despite declining kidney function 3, 5.
Monitoring After Initiation
Expect an initial eGFR decline of approximately 4-5% in the first month after starting tolvaptan due to suppression of glomerular hyperfiltration and potential volume depletion effects 6.
This initial decline is actually a favorable prognostic indicator—patients with larger initial eGFR drops tend to have better long-term renal outcomes, suggesting effective pharmacological response 6.
Monitor serum creatinine, electrolytes, and volume status within 2-4 weeks of initiation and regularly thereafter 3, 4.
Important Caveats
Do not confuse the initial expected eGFR decline with acute kidney injury—an acute drop up to 30% can represent therapeutic effect rather than harm, similar to what occurs with ACE inhibitors and ARBs 7, 6.
Temporarily withhold tolvaptan during prolonged fasting, surgery, or critical illness when ketosis risk is elevated 3.
The CKD-EPI equation performs adequately in ADPKD patients despite increased tubular secretion of creatinine in this population, so standard eGFR calculations remain valid for dosing decisions 8.
Practical Algorithm
- Confirm ADPKD diagnosis and assess progression risk using imaging (htTKV), genetic testing, or urinary biomarkers 2
- Check baseline eGFR—if ≥25 mL/min/1.73 m², patient is eligible for initiation 1
- Start tolvaptan and recheck eGFR at 2-4 weeks—expect 4-5% decline 6
- Continue therapy indefinitely even as eGFR falls below 25 mL/min/1.73 m² 3, 4
- Discontinue only at dialysis initiation or if intolerance develops (severe aquaresis, hepatotoxicity) 3