Lyrica to Gabapentin Conversion

There is no established conversion ratio between pregabalin (Lyrica) and gabapentin because they have fundamentally different pharmacokinetics that prevent direct dose equivalence.

The evidence-based approach is to transition from one agent to the other using a gradual cross-titration protocol, not a mathematical conversion.

Pregabalin has linear pharmacokinetics with >90% oral bioavailability, meaning dose increases produce proportional blood level increases, while gabapentin has nonlinear, saturable absorption that becomes progressively less efficient at higher doses. 1
The maximum dose of gabapentin is 3600 mg/day compared to 600 mg/day for pregabalin, but this 6:1 ratio does not represent therapeutic equivalence—it reflects their different absorption profiles, not equal efficacy. 2
Pregabalin achieves therapeutic effect at substantially lower doses than gabapentin because it binds the α2δ calcium channel subunit with greater affinity, despite sharing the same mechanism of action. 1

Stop gabapentin completely and start pregabalin 75 mg twice daily (150 mg/day total) at the next scheduled dose. 2
Pharmacokinetic modeling demonstrates that pregabalin-equivalent concentrations are achieved within 1 day of pregabalin initiation when using immediate discontinuation. 3
This approach is appropriate for most patients and avoids the additive sedative burden of combining two gabapentinoids. 1

Continue the morning dose of gabapentin while starting pregabalin 75 mg twice daily for the first few days, then gradually taper gabapentin over several days to weeks. 2
The American Academy of Neurology recommends this approach specifically to avoid withdrawal symptoms in patients on chronic, high-dose gabapentin therapy. 2
Pharmacokinetic simulations show that coadministering 50% of the gabapentin dose with 50% of the target pregabalin dose for 4 days, followed by full pregabalin dosing, maintains stable drug exposure throughout the transition. 3

All patients should start pregabalin at 150 mg/day regardless of their gabapentin dose, because pregabalin's linear pharmacokinetics and superior bioavailability make this the evidence-based starting point. 1, 2
Increase to 300 mg/day (150 mg twice daily) within 1 week based on efficacy and tolerability—this is the standard effective dose with optimal benefit-to-risk ratio. 1, 2
The 300 mg/day pregabalin dose provides comparable or superior efficacy to gabapentin 1800–3600 mg/day for neuropathic pain, with faster onset of relief (1.5–3.5 days vs. several weeks). 1

Do not combine gabapentin and pregabalin routinely—they share identical mechanisms and adverse effect profiles, creating unacceptable additive sedative burden (dizziness, somnolence, fall risk) without established efficacy benefit. 1, 4
There are no randomized controlled trials demonstrating that combining gabapentin and pregabalin is superior to optimizing the dose of either medication alone. 1
The World Journal of Emergency Surgery specifically warns that combining gabapentinoids increases postoperative sedation, dizziness, and visual disturbances, with synergistic CNS depression particularly dangerous in elderly patients. 1

Start pregabalin at 25–50 mg/day (not the standard 150 mg/day) and implement slow weekly titration to minimize dizziness, confusion, and fall risk. 1, 2
Elderly patients are more susceptible to falls, confusion, and sedation from gabapentinoids, and age-related decline in renal function (often masked by normal serum creatinine) compounds this risk. 1, 2

Mandatory dose reduction is required for both gabapentin and pregabalin because both are eliminated unchanged by the kidneys (95% pregabalin, similar for gabapentin). 1, 2
For pregabalin, reduce total daily dose by approximately 50% for CrCl 30–60 mL/min, 75% for CrCl 15–30 mL/min, and 85–90% for CrCl <15 mL/min. 2
Always calculate creatinine clearance (Cockcroft-Gault or CKD-EPI) before initiating pregabalin—do not rely on serum creatinine alone, especially in elderly patients with reduced muscle mass. 2

Do not assume a 6:1 conversion ratio (e.g., gabapentin 1800 mg = pregabalin 300 mg) is therapeutically valid—this oversimplifies their pharmacokinetic differences and lacks clinical trial support. 1, 3
Do not switch to pregabalin if gabapentin failed—patients may respond to one, both, or neither, and there is no evidence supporting sequential gabapentinoid use as a strategy. 1
Do not abruptly discontinue gabapentin in patients on chronic high-dose therapy (≥1800 mg/day for >3 months)—taper gradually over at least 1 week to avoid withdrawal symptoms (anxiety, insomnia, nausea, pain, sweating). 1, 2
Do not use pregabalin doses >300 mg/day routinely—higher doses (up to 600 mg/day) are not consistently more effective but significantly increase adverse effects (dizziness 23–46%, somnolence 15–25%, peripheral edema 10%). 1, 2

Twice-daily dosing (vs. mandatory three-times-daily for gabapentin) improves adherence. 1
Faster onset of pain relief (1.5–3.5 days vs. 4–8 weeks for gabapentin to reach therapeutic effect). 1
Predictable dose-response relationship due to linear pharmacokinetics, making titration straightforward. 1, 2
No saturable absorption, so higher doses produce proportional increases in blood levels (unlike gabapentin, where absorption efficiency decreases at doses >1200 mg). 1

Cost is the primary barrier—generic gabapentin is substantially less expensive than pregabalin, so transition should be reserved for patients with documented adherence problems, intolerable side effects from three-times-daily dosing, or inadequate response despite optimal gabapentin titration (1800–3600 mg/day for ≥2 months). 1
Pregabalin is preferred in elderly patients with comorbidities (diabetes, renal impairment) due to superior pharmacokinetic profile and easier titration. 1