What is the recommended dose, frequency, and duration of gabapentin (Neurontin) versus pregabalin (Lyrica) for treating low back pain, and how do their side effect profiles compare?

Gabapentinoids for Low Back Pain: Limited Role and Significant Cautions

Neither pregabalin nor gabapentin should be used for chronic low back pain without radiculopathy, as they provide no benefit and cause substantial adverse effects; for radicular pain specifically, gabapentin may offer small benefits at 1200-3600 mg/day divided three times daily for 6-10 weeks, while pregabalin shows no advantage and may worsen function. 1, 2, 3

Critical Distinction: Radicular vs. Axial Pain

The American College of Physicians explicitly states that gabapentinoids are effective only for radicular/sciatic pain, not for chronic axial low back pain. 1 This distinction is paramount:

• For radicular pain with radiculopathy: Gabapentin shows small to moderate short-term benefits in trials lasting 6-10 weeks 4, 2
• For nonradicular chronic low back pain: Gabapentinoids demonstrate no benefit and significant risk of adverse effects 1, 3

Dosing Protocols When Indicated

Gabapentin (for radicular pain only)

• Starting dose: Titrate gradually to minimize adverse effects 4
• Target dose: 1200-3600 mg/day divided three times daily 2
• Duration: 6-10 weeks in clinical trials 4
• Renal adjustment required: Reduce dose in patients with eGFR 37-50 mL/min to avoid accumulation and toxicity 1

Pregabalin (generally not recommended)

• Typical dose in studies: 300 mg/day 5
• Evidence: Shows no benefit for chronic nonradicular back pain and may actually worsen function 2
• Comparative efficacy: One pilot trial found pregabalin 300 mg/day superior for pain reduction compared to gabapentin 800 mg/day, but gabapentin demonstrated better effects on anxiety, insomnia, and fatigue 5

Side Effect Profiles

Gabapentin

The number needed to harm demonstrates clinically significant risks 3:

• Dizziness: 7 patients (RR 1.99) - very low quality evidence 3
• Fatigue: 8 patients (RR 1.85) - very low quality evidence 3
• Difficulties with mentation: 6 patients (RR 3.34) - low quality evidence 3
• Visual disturbances: 6 patients (RR 5.72) - moderate quality evidence 3
• Additional effects: Drowsiness (6%), loss of energy (6%), dizziness (6%) 4

Pregabalin

• Higher withdrawal rates: 33% vs. 15% with active placebo in one trial 4
• Balance impairment: Adverse effects on balance at initial doses and dose increments, though tolerance develops at maintenance doses 6
• Common adverse events: Sedation (34% vs. 3% with diphenhydramine), diarrhea (30% vs. 10%) 4

Clinical Decision Algorithm

Step 1: Determine Pain Type

• If radicular pain/sciatica present: Consider gabapentin as part of multimodal therapy 2
• If purely axial low back pain: Do NOT use gabapentinoids; switch to alternatives 1

Step 2: For Radicular Pain

• First-line: NSAIDs for inflammatory component 2
• Add gabapentin: For neuropathic component, titrate to 1200-3600 mg/day divided TID 2
• Monitor closely: Assess for sedation, dizziness, peripheral edema 2
• Reassess at 6-10 weeks: If no response, discontinue 2

Step 3: Superior Alternatives for Chronic Low Back Pain

• Tricyclic antidepressants (amitriptyline): Moderate efficacy with higher-quality evidence 1, 2
• Duloxetine: Modest improvement in pain intensity and function 1, 2
• NSAIDs: First-line for short-term pain relief 1

Critical Pitfalls to Avoid

Do not prescribe gabapentinoids for nonspecific chronic low back pain. The American College of Physicians recommends against this practice due to lack of benefit and significant adverse effect risk. 1 A 2017 systematic review and meta-analysis found very low quality evidence showing minimal improvement (MD = 0.22 units) with substantial harm. 3

Do not use pregabalin as first-line. When compared head-to-head, pregabalin was slightly less efficacious than amitriptyline, tramadol/acetaminophen, and celecoxib, and adding pregabalin to celecoxib showed no additional benefit. 7

Always adjust for renal function. Failure to reduce gabapentin dosing in moderate renal impairment leads to drug accumulation and increased toxicity. 1

Recognize the evidence quality is poor. Most gabapentin trials for radiculopathy were poor-quality with inconsistent findings, and neither medication is FDA-approved specifically for low back pain. 2

When to Stop Gabapentinoids

For patients currently on pregabalin for chronic axial low back pain: Stop pregabalin and switch to an antidepressant (amitriptyline) or duloxetine. 1 Re-evaluate the nature of pain to determine if there is a radicular component; if confirmed, gabapentin may be considered with strict renal adjustment. 1