Concurrent Use of Regular Gabapentin and Horizant (Gabapentin Enacarbil)
Taking regular gabapentin during the day while already on Horizant (gabapentin enacarbil) is not recommended due to the risk of additive side effects without clear evidence of additional benefit.
Understanding the Medications
Horizant (gabapentin enacarbil): An extended-release prodrug of gabapentin approved for restless legs syndrome 1, 2
- Converts to gabapentin in the body
- Provides sustained gabapentin levels throughout the day
- Usually dosed once daily at 600 mg 3
Regular gabapentin: Immediate-release formulation approved for epilepsy and neuropathic pain 4
- Shorter half-life requiring multiple daily doses
- Typically dosed 3 times daily at 300-1200 mg per dose
Reasons to Avoid Concurrent Use
Pharmacological redundancy: Both medications deliver the same active compound (gabapentin) to the body
Risk of adverse effects: Combining both formulations increases the risk of dose-dependent side effects:
- Somnolence/sedation
- Dizziness
- Fatigue
- Peripheral edema 3
Potential toxicity: Excessive gabapentin levels can be dangerous, with documented fatality at very high blood concentrations 5
Alternative Approaches for Pain Management
If you're taking Horizant for restless legs syndrome but need pain management during the day, consider these evidence-based alternatives:
For neuropathic pain:
- Pregabalin (300-600 mg/day)
- Duloxetine (60-120 mg daily)
- Amitriptyline (10-25 mg at bedtime, increasing to 50-150 mg) 6
For chronic cough (if that's the indication):
- The CHEST Cough Expert Panel suggests gabapentin as a therapeutic trial for unexplained chronic cough, but doesn't recommend concurrent use of multiple gabapentinoids 7
- Recommended gabapentin dosing for cough: starting at 300 mg once daily with dose escalation up to 1,800 mg daily in two divided doses 7
What to Discuss with Your Doctor
If your current gabapentin regimen isn't providing adequate symptom control:
Adjust Horizant dosing: Consider discussing with your doctor whether a higher dose of Horizant alone might be more appropriate
Switch to regular gabapentin only: If you need more flexible dosing throughout the day, switching completely to regular gabapentin with multiple daily doses may be preferable
Consider alternative medications: Based on your specific condition, other medication classes may be more appropriate
Monitoring if Concurrent Use is Attempted
If a provider does decide to try concurrent therapy (which is generally not recommended):
- Start with the lowest possible dose of regular gabapentin
- Monitor closely for excessive sedation, dizziness, and other side effects
- Be particularly cautious in elderly patients or those with renal impairment
- Establish clear criteria for discontinuation if side effects occur
Remember that the goal of therapy should be symptom control with the simplest, safest medication regimen possible.