Crystal nephropathy and amoxicillin: insights from international spontaneous reporting systems

A substantial increase in amoxicillin-induced crystal nephropathy was recently reported in France. Our study aims to further characterize this safety issue from a worldwide perspective.

We queried both the FDA Adverse Event Reporting System (FAERS) and the Eudravigilance databases, and performed disproportionality analysis, selecting only adverse events (AEs) related to crystal nephropathy where amoxicillin or amoxicillin/clavulanic acid were reported as suspect. In FAERS, the reporting odds ratios were calculated and deemed significant by the lower limit of the 95% confidence interval (LL95%CI) > 1, selecting all other drugs/events recorded in FAERS as comparator. Deduplication followed by case-by-case assessment and comparison between French and non-French cases were also performed in both databases.

Overall, 57,754 and 84,764 AE reports with amoxicillin or amoxicillin/clavulanic acid were recorded in FAERS and Eudravigilance, respectively, with France accounting for 18.7% and 22.0% of cases. Specific AEs of interest were retrieved in 144 and 239 cases, respectively. Increased reporting was found in FAERS for crystalluria (N = 99; LL95%CI 53.18), crystal nephropathy (24; 27.01), medication crystal in urine present (9; 92.00), crystal urine (8; 11.90), and crystal urine present (4; 1.57). In FAERS and Eudravigilance databases, reports were classified as serious in 98.8% and 91.2% of cases, respectively. Acute kidney injury (AKI) was found in 81.2% and 71.1% of patients. Amoxicillin was mainly given intravenously, and a dose ≥ 12 g/day was administered in 50.0% and 19.7% of cases in the FAERS and Eudravigilance databases, respectively.

Although causal association cannot be firmly inferred, a consistent signal of crystal nephropathy with amoxicillin emerged, especially in France. Clinicians should monitor patients for possible early AKI onset, especially when dealing with intravenous administration of daily doses > 12 g.