MT-RNR1 genotype testing for preventing aminoglycoside-mediated ototoxicity: A guideline developed by the UK Centre of Excellence in Regulatory Science and Innovation in Pharmacogenomics (CERSI-PGx).

Aminoglycosides are broad-spectrum antibiotics used in the management of severe infections. Aminoglycosides are associated with nephrotoxicity and ototoxicity. Although dosing strategies such as once-daily administration and therapeutic drug monitoring have reduced the incidence of nephrotoxicity, ototoxicity remains unpredictable and may occur at therapeutic concentrations. A strong association between specific mitochondrial DNA variants in MT-RNR1 (m.1555A > G, m.1494C > T and m.1095 T > C) and aminoglycoside-induced hearing loss exists. These variants (frequency ~1 in 330 individuals across populations) predispose to irreversible, sensorineural hearing loss following aminoglycoside exposure, sometimes after a single dose. Avoidance of aminoglycosides is recommended at any detectable variant level. In England, laboratory-based MT-RNR1 testing is nationally commissioned, whereas point-of-care testing in time-critical settings like neonatal sepsis is delivered in some centres. Approximately 20% of aminoglycoside use is predictable providing opportunities for pre-emptive pharmacogenetic testing. Where MT-RNR1 testing results are unavailable and clinical urgency is high, aminoglycoside treatment should not be delayed. Early health economic evidence suggests that point-of-care testing in neonates may be cost-saving by preventing lifelong hearing loss. Regulatory and Health Technology Assessment bodies support targeted implementation of testing alongside further evidence generation. Overall, integration of MT-RNR1 pharmacogenetic testing offers a feasible and proportionate strategy to reduce harm while preserving access to life-saving antibiotic therapy. This guideline is grounded in the latest evidence in this field but cannot account for all individual factors relevant to patient care. Therefore, prescribers must conduct a thorough assessment of each patient's risk-benefit profile, ensuring that therapy is optimized to maximize benefits while minimizing potential harms.