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Gabapentin to Pregabalin Conversion — FRCA Final MCQ

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ModeratePain MedicineGabapentin to Pregabalin ConversionFRCA Final

A 55-year-old man (ASA II) with chronic lower back pain has been on gabapentin 300 mg TDS for 6 months with moderate benefit. He would like to try pregabalin instead. What is the approximate conversion ratio from gabapentin to pregabalin?

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Correct answer: B — Pregabalin dose is approximately 1/6th of the gabapentin dose

The approximate conversion ratio from gabapentin to pregabalin is approximately 6:1 (gabapentin:pregabalin). Therefore, gabapentin 900 mg/day ≈ pregabalin 150 mg/day. Pregabalin has superior bioavailability (~90% vs ~60% for gabapentin at low doses, decreasing to ~30% at high doses), more predictable pharmacokinetics (linear absorption), and faster onset. Cross-titration can be done over 1-2 weeks: start pregabalin at equivalent dose while gradually reducing gabapentin. An abrupt switch without tapering gabapentin risks withdrawal symptoms.

Reference: BNF – 2025 – Gabapentinoid conversion; Faculty of Pain Medicine – 2021 – Neuropathic pain prescribing