Amoxicillin crystalluria
Paula Mato-Martínez, Leire Cardo, Diana Arteaga-MenaAbstract
Objectives
Amoxicillin is a widely used beta-lactam antibiotic. Although it is a rare cause of urolithiasis, there are situations in which its solubility in urine decreases, leading to stone formation and potential kidney injury.
Case presentation
A 63-year-old woman, with a history of breast carcinoma and cognitive impairment was treated for 4 days with amoxicillin/clavulanic acid for an arm inflammation. She presented with symptoms of urolithiasis and acute inflammatory markers. Urinalysis revealed abundant needle-shaped crystals morphologically compatible with amoxicillin. The diagnosis was supported by the observation of a characteristic chromatographic interference during amino acid analysis (liquid chromatography cation exchange with post-column ninhydrin derivatization).
Conclusions
Although amoxicillin crystalluria has been previously described, it is not a common entity, which can lead to underdiagnosis due to non-identification/misidentification of the urinary crystals. Therefore, detection and identification of crystalluria in these patients through urinary sediment analysis is important to prevent complications such as obstructive nephropathy. The description of amoxicillin crystals, along with the results of the chromatographic analysis we present, will help to identify the etiology of the crystalluria, making it possible to distinguish that caused by amoxicillin from other drug-induced crystalluria with similar morphology, using a methodology widely available in clinical laboratories.