Proton pump inhibitors (PPIs) are emerging as an important contributing cause to acute interstitial nephritis (AIN), a study found. These medications are the most common cause of AIN in the outpatient setting.

Angela K. Muriithi, MBChB, MPH, of Mayo Clinic in Rochester, Minn., and colleagues retrospectively studied 133 patients with biopsy-proven AIN. Drugs were the cause in 70% of cases, autoimmune diseases, 20%, and infections, 4%. Results showed that 49% of the drug-related cases were due to antibiotics, 14% were due to PPIs, and 11% were due to non-steroidal anti-inflammatory agents.

The top 3 drug causes were omeprazole (12%), amoxicillin (8%), and ciprofloxacin (8%), the researchers reported online ahead of print in the American Journal of Kidney Diseases. Patients with drug-related AIN were older and had higher baseline kidney function than those with non-drug-related AIN, but more severe acute kidney injury.

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At 6 months post-biopsy, 49% of patients with drug-induced AIN treated with steroids achieved complete recovery, 39% had partial receovery, and 12% had no recovery. Longer duration of drug exposure and longer delays in starting steroid therapy were associated with poor recovery.