How should I manage fatigue and periodic limb movement disorder in a patient taking Rexulti (brexpiprazole), ropinirole, and doxepin?

Managing Fatigue and PLMD in a Patient on Rexulti, Ropinirole, and Doxepin

The ropinirole is likely contributing to both the PLMD and fatigue through augmentation, and should be gradually withdrawn while transitioning to gabapentin or pregabalin as first-line therapy; doxepin appears safe to continue, and iron status must be checked immediately.

Immediate Assessment Required

Check iron studies (ferritin and transferrin saturation) in the morning after 24-hour avoidance of iron supplements:

• If ferritin ≤75 ng/mL or transferrin saturation <20%: initiate oral or IV iron therapy 1
• If ferritin 75-100 ng/mL: consider IV iron only 1
• Target ferritin >100 ng/mL 2

The Ropinirole Problem

The 2025 AASM guidelines represent a paradigm shift: the AASM now suggests AGAINST the standard use of ropinirole for RLS/PLMD (conditional recommendation, moderate certainty of evidence) 1. This is critical because:

• Dopamine agonists like ropinirole cause augmentation—a worsening of RLS/PLMD symptoms despite treatment, which manifests as increased severity, earlier onset in the day, and spread to other body parts 1, 3
• Augmentation likely explains your patient's persistent PLMD and may be contributing to fatigue through disrupted sleep architecture
• The guidelines explicitly state ropinirole may only be used short-term in patients who prioritize immediate symptom relief over long-term adverse effects 1

Medication-Specific Analysis

Rexulti (brexpiprazole):

• While the FDA label doesn't specifically mention RLS/PLMD, atypical antipsychotics can theoretically worsen these conditions 4
• However, research on olanzapine (a related antipsychotic) showed RLS that was refractory to ropinirole, suggesting antipsychotic-induced RLS may have mechanisms beyond simple dopamine depletion 5
• Do not discontinue without psychiatric consultation, as this is treating a primary psychiatric condition

Doxepin:

• Good news: sedating antidepressants like doxepin do NOT appear to aggravate periodic limb movements 6
• This can be safely continued

Ropinirole:

• Must be addressed as outlined below

Treatment Algorithm

Step 1: Optimize Iron (Immediate)

• Check morning iron studies
• Initiate appropriate iron supplementation based on levels above
• IV ferric carboxymaltose has strong evidence (strong recommendation, moderate certainty) 1

Step 2: Transition from Ropinirole to Alpha-2-Delta Ligands

First-line options (all strong recommendations, moderate certainty) 1:

1. Gabapentin enacarbil (preferred if available)
2. Gabapentin
3. Pregabalin

Transition strategy:

• Start gabapentin (1200-1800 mg/day) or pregabalin (150-450 mg/day) while ropinirole is still on board 7, 8
• Once alpha-2-delta ligand is at therapeutic dose, gradually taper ropinirole (expect temporary symptom worsening during taper) 3
• May need temporary clonazepam during the transition, though AASM suggests against routine clonazepam use (conditional recommendation, very low certainty) 1, 3

Step 3: If Refractory After Above Measures

Consider extended-release oxycodone or other opioids (conditional recommendation, moderate certainty) 1. Recent data from the National RLS Opioid Registry shows reassuring safety findings 8.

Critical Pitfalls to Avoid

1. Do not simply increase ropinirole dose—this will worsen augmentation 3, 2
2. Do not abruptly stop ropinirole—taper gradually to avoid severe rebound 3
3. Do not assume PLMD requires separate treatment from RLS—they often coexist and respond to the same therapies 1
4. Do not overlook iron even if "normal"—RLS/PLMD requires higher ferritin targets (>100 ng/mL) than general population 1, 2

Addressing the Fatigue

The fatigue is likely multifactorial:

• PLMD-related sleep disruption: PLMS cause EEG arousals and elevations in heart rate/blood pressure, fragmenting sleep 1
• Augmentation from ropinirole: worsening symptoms lead to poor sleep quality 3
• Possible Rexulti contribution: drowsiness is a known side effect 4

Treating the PLMD as outlined above should improve sleep architecture and reduce fatigue. Monitor for orthostatic hypotension from Rexulti, which can also cause fatigue 4.

Evidence Strength Summary

The 2025 AASM guidelines 1 represent the highest quality, most recent evidence and fundamentally changed RLS/PLMD management by downgrading dopamine agonists from first-line to discouraged therapy 8, 9, 2. This shift is based on accumulating evidence of augmentation risk with long-term dopaminergic therapy 10, 8.