What is the equivalent dose of gabapentin (Gabapentin) for a patient taking 150mg of Lyrica (Pregabalin)?

Pregabalin to Gabapentin Dose Conversion

There is no established direct conversion ratio between pregabalin 150 mg and gabapentin, but based on maximum dose ratios (pregabalin 600 mg/day vs gabapentin 3600 mg/day), a 1:6 ratio suggests approximately 900 mg/day of gabapentin as a rough equivalent to pregabalin 150 mg/day. 1

Critical Limitations of Conversion

• No validated conversion formula exists between these medications 1
• Pregabalin has linear, predictable pharmacokinetics with 90% oral bioavailability, while gabapentin has nonlinear, saturable absorption that becomes less efficient at higher doses 1
• Patients may respond to one medication, both, or neither—response to pregabalin does not predict response to gabapentin 2
• The medications are not interchangeable on a milligram-per-milligram basis 1

Practical Approach to Switching

Starting Gabapentin After Pregabalin 150 mg

Begin gabapentin at 300 mg three times daily (900 mg/day total) while tapering pregabalin gradually over several days to weeks 1, 2

• Start gabapentin at 100-300 mg at bedtime on day 1, then increase to 300 mg three times daily by day 3 2
• Continue morning dose of pregabalin for at least the first few days while initiating gabapentin 1
• Taper pregabalin gradually over a minimum of 1 week to avoid withdrawal symptoms 1
• Titrate gabapentin by 300 mg every 3-7 days as tolerated toward target dose of 1800-3600 mg/day in three divided doses 2, 3

Expected Timeline

• Gabapentin requires 3-8 weeks for titration plus 2 weeks at maximum tolerated dose to properly evaluate efficacy—an adequate trial may require 2 months or more 2, 3
• This is substantially longer than pregabalin, which achieves pain relief within 1.5-3.5 days 1

Dosing Comparison Framework

Pregabalin 150 mg/day

• Typically administered as 75 mg twice daily 1
• This is the starting dose, not the therapeutic dose 1
• Standard therapeutic dose is 300 mg/day (150 mg twice daily) 1

Gabapentin Equivalent Range

• Starting dose: 900 mg/day (300 mg three times daily) 2, 3
• Target therapeutic dose: 1800-3600 mg/day in three divided doses 2, 3
• The 1:6 ratio (based on maximum doses of 600 mg pregabalin vs 3600 mg gabapentin) suggests 900 mg gabapentin for 150 mg pregabalin 1

Critical Pitfalls to Avoid

• Never assume equivalent efficacy—approximately 32-38% of patients achieve at least 50% pain reduction with gabapentin at therapeutic doses, but individual response varies 2
• Do not use once-daily or twice-daily dosing for standard gabapentin—three times daily administration is essential due to saturable absorption 2
• Do not rush titration—slower increases every 3-7 days minimize adverse effects, particularly dizziness and somnolence 2, 3
• Do not fail to assess renal function—both medications require mandatory dose reduction in renal impairment, as they are eliminated primarily by renal excretion 1, 2
• Do not abruptly discontinue pregabalin—taper gradually over minimum of 1 week when switching 1

Special Considerations

Elderly Patients

• Start gabapentin at lower doses (100-200 mg/day) with slower titration 2
• Calculate creatinine clearance before initiating therapy, as age-related decline in renal function is often masked by normal serum creatinine 1

Renal Impairment

• Dose adjustment is mandatory for both medications based on creatinine clearance 1, 2
• For CrCl 30-60 mL/min: reduce pregabalin dose by approximately 50%; for gabapentin, adjust to 200-700 mg/day 1, 2

Adverse Effects

• Both medications cause identical adverse effects: dizziness (23-46% with pregabalin, 19% with gabapentin), somnolence (15-25% with pregabalin, 14% with gabapentin), and peripheral edema 1, 4, 5
• These effects are dose-dependent and often transient, typically subsiding within approximately 10 days 2, 4