1179 An Unshakeable Case of Refractory RLS- Androgen Receptor Inhibitor Therapy as a Cause of RLS Exacerbation

Introduction Restless leg syndrome (RLS/WED) is a neurological sleep condition which is characterized by an uncontrollable urge to move an individual’s legs and sometimes arms when at rest. Symptoms typically arise in the evening and nighttime hours and can be associated with severe insomnia and negative impact on quality of life. Here we present a case of severe RLS/WED exacerbations temporally associated with androgen receptor inhibitor therapy. Report of case(s) A 58 year old male was referred to the sleep medicine clinic for refractory RLS/WED. He was previously treated with high dose ropinirole, which was associated with severe augmentation. Trials of gabapentin, pregabalin, tramadol, and hydrocodone were associated with persistence of severe symptoms. He was eventually treated with methadone at a dose of 10 mg in addition to Rotigotine patch at a dose of 2 mg, with adequate symptom relief. He was later diagnosed with prostate cancer, and initiated on enzalutamide, an androgen receptor inhibitor. Within two weeks of starting this medication, he had a severe exacerbation of his RLS symptoms and associated insomnia. The medication was discontinued, with subsequent abatement of RLS symptoms. He was then switched to apalutamide by his urologist (another androgen receptor inhibitor), but again developed severe RLS exacerbation. Dosing of the Rotigotine patch and methadone were increased to 4 mg and 12.5 mg daily respectively. In addition, he was started on pramipexole 0.25 mg, which was later increased to 0.5 mg, but he continued to have severe residual symptomatology. After discussing with his oncologist, he went on a trial of 3-4 weeks where apalutamide was discontinued. During this time, his RLS symptoms resolved, and he was sleeping well. He then restarted apalutamide and again experienced a similar a severe RLS flare. Conclusion Our case demonstrates an association between androgen receptor inhibitor therapy and RLS exacerbations. Further work is needed to understand the possible relationships between RLS and these common treatments for prostate cancer. Support (if any)