# Lower incidence of diabetic retinopathy and worsening events after phentermine assisted weight loss across a large U.S. cohort

## TL;DR

Using phentermine for weight loss is linked to lower risks of diabetic retinopathy and related complications in a large U.S. study.

## Contribution

This study is the first to show that phentermine reduces the risk of diabetic retinopathy and its progression in obese patients.

## Key findings

- Phentermine use was associated with a 54% lower risk of new diabetic macular oedema diagnoses.
- Patients using phentermine had a 47% reduced risk of proliferative diabetic retinopathy.
- The medication was linked to a 66% lower risk of vitreous haemorrhage.

## Abstract

Medication assisted weight loss for treatment of obesity has rapidly increased. The effect of this treatment with phentermine on diabetic retinopathy (DR) is underexplored.

Retrospective cohort study. The U.S. Collaborative Network of the TriNetX platform was queried for patients diagnosed with overweight and obesity and prescription of phentermine. Patients were propensity score matched across baseline demographics and systemic risk factors at the time of medication initiation and compared to those diagnosed with overweight and obesity without usage of weight loss medications, identifying 26,611 patients per cohort after propensity score matching. Risk ratios (RR) of incident DR and related diagnoses or procedural codes found after the medication initiation date for pertinent disease worsening and treatment metrics were assessed.

Phentermine usage was found to be associated with reduced future risk of a new diagnosis of DR with macular oedema (RR 0.462; (95% CI 0.372–0.573), P < 0.001), mild non-proliferative diabetic retinopathy (NPDR) (RR 0.621 (0.508, 0.760), P < 0.001), moderate NPDR (RR 0.567 (0.402, 0.799), P < 0.001), severe NPDR (RR 0.477 (0.233, 0.981), P = 0.003), proliferative diabetic retinopathy (PDR) (RR 0.451 (0.323, 0.629), P < 0.001), vitreous haemorrhage (RR 0.347 (0.200, 0.602), P < 0.001), need for intravitreal anti-VEGF injection (RR: 0.530 (0.354, 0.793), P < 0.001).

The present analysis suggests that phentermine usage is associated with a decreased risk of diabetic macular oedema, NPDR, PDR, and worsening events.