Fixed-Dose Combination Product
No FDA-approved fixed-dose combination product exists that combines gabapentin and cobalamin (vitamin B12) in a single formulation.
Available Formulations
- Gabapentin (Neurontin) is available only as a standalone medication in capsule, tablet, and oral solution forms 1
- Cobalamin (vitamin B12) is available separately as oral supplements, sublingual tablets, and injectable formulations 2
- These medications must be prescribed and administered as separate agents if both are clinically indicated 1
Clinical Context for Combined Use
- A clinical trial evaluated gabapentin combined with B-complex vitamins (thiamine B1 100 mg and cyanocobalamin B12 20 mg) for painful diabetic neuropathy, demonstrating efficacy comparable to pregabalin 1
- The combination of gabapentin with B vitamins achieved pain reduction at approximately 50% of the typical gabapentin monotherapy dose (900 mg versus 1600-3200 mg daily) 1
- This combination also resulted in significantly less vertigo and dizziness compared to pregabalin monotherapy (P = 0.014) 1
Practical Prescribing Approach
- If both agents are clinically warranted, prescribe gabapentin and vitamin B12 as separate medications 1
- For neuropathic pain with suspected B12 deficiency, screen with at least two biomarkers (holo-TC, MMA) or serum cobalamin before initiating therapy 2
- Standard B12 supplementation provides 2.5 mcg daily for general maintenance, with higher doses (5 mcg parenterally) for documented deficiency 2
- Gabapentin dosing for neuropathic pain typically starts at 100-300 mg nightly and titrates to 900-3600 mg daily in divided doses, with renal adjustment as needed 3
Important Safety Considerations
- Avoid therapeutic duplication by ensuring patients are not prescribed both gabapentin and pregabalin simultaneously, as this increases adverse effects without additional benefit 4
- Monitor for dose-dependent peripheral edema and CNS depression (dizziness, somnolence) with gabapentin, particularly in elderly patients or those with cardiac history 5
- No upper toxicity limit exists for cobalamin, though excessive supplementation combined with folic acid and pyridoxine may accelerate renal decline in diabetic nephropathy 2