Evidence of a gabapentinoid and diuretic prescribing cascade among older adults with lower back pain.

Background/objectives: Gabapentinoids are commonly prescribed to relieve pain. The development of edema, an established adverse effect of gabapentinoids, may lead to a potentially harmful prescribing cascade whereby individuals are subsequently prescribed diuretics and exposed to diuretic-induced adverse events. The frequency of this prescribing cascade is unknown. Our objective was to measure the association between new dispensing of a gabapentinoid and the subsequent dispensing of a diuretic in older adults with new low back pain.

Design: Population-based cohort study.

Setting: Ontario, Canada.

Participants: A total of 260,344 community-dwelling adults aged 66 years or older, newly diagnosed with low back pain between April 1, 2011, and March 31, 2019.

Measurements: Exposure status was assigned using dispensed medications in the 1 week after low back pain diagnosis. Older adults newly dispensed a gabapentinoid (N = 7867) were compared with older adults who were not newly dispensed a gabapentinoid (N = 252,477). Hazard ratios (HRs) with 95% confidence intervals (CIs) for dispensing of a diuretic within 90 days of follow-up among older adults prescribed gabapentin relative to those who were not.

Results: Older adults newly dispensed a gabapentinoid had a higher risk of being subsequently dispensed a diuretic within 90 days compared with older adults who were not prescribed a gabapentinoid (2.0% vs. 1.3%). After covariate adjustment, new gabapentinoid users had a higher rate of being dispensed a diuretic compared with those not prescribed a gabapentinoid (HR: 1.44, 95% CI: 1.23, 1.70). The rate of diuretic prescription among new gabapentinoid users increased with increasing gabapentinoid dosages.

Conclusions: We have demonstrated the presence of a potentially inappropriate and harmful prescribing cascade. Given the widespread use of gabapentinoids, the population-based scale of this problem may be substantial. Increased awareness of this prescribing cascade is required to reduce the unnecessary use of diuretics and the exposure of patients to additional adverse drug events.