How to Convert Patients from Neurontin® to Lyrica®

Patient Case

  • BT is a 57 year-old male admitted to the burn treatment unit for lower extremity frostbite
  • The patient received a trans-metatarsal amputation of all toes in the right foot
  • He is currently taking gabapentin 600 mg TID for neuropathic pain
  • However, BT still complains of zinging pain in the lower extremities

Drug Information Question

The physician wants to switch BT from gabapentin (Neurontin®) to pregabalin (Lyrica®). She asks the pharmacy team: “What would be an appropriate starting dose of pregabalin for this patient?”

Scenario

The patient case/scenario above is based on a true experience I had during my acute care rotation at Crozer Health’s Burn Treatment Center (BTC).

During rounds with the medical team, this question came up and I was asked to quickly perform a literature review to come up with an accurate recommendation.

Of note, pregabalin’s package insert only has information on starting dosages. Therefore, a more in-depth search was needed to properly transition this patient from one medication to the other.

Clinical Data Summary

Current guidelines for the management of neuropathic pain do not have specific recommendations for how to switch from gabapentin to pregabalin.

However, there are population pharmacokinetic (PK) and clinical studies that have explored appropriate conversion between the two medications and provide some guidance for dosing.1-3

  • A  population PK study by Bockbrader, et. al., used a ratio of 6:1 when evaluating the conversion from gabapentin to pregabalin.1
  • Another study calculated that the analgesic effects of pregabalin are about six times greater than those of gabapentin.2
  • Finally, a trial by Toth C. utilized a conversion algorithm that roughly equates to a gabapentin-to-pregabalin ratio of 6:1.3

Response

Because BT was taking 1800 mg of Neurontin® daily at the time, I recommended that Lyrica® be started at 150 mg BID.

In the context of neuropathic pain, BT could take his last dose of Neurontin® that evening and start Lyrica® the following morning.

However, if the indication was for seizure management, a tapering approach would have been more appropriate.1-3

The Bottom Line

Patient care in a critical or intensive unit setting is very dynamic and pharmacotherapy can change very quickly. There are many patient-specific factors to consider while also juggling multi-disciplinary relationships.

Although answers may be needed quickly, taking the time to review appropriate drug information resources can make the difference between appropriate patient care and medication errors.

References

  1. Bockbrader HN, Wesche D, Miller R, Chapel S, Janiczek N, Burger P. A comparison of the pharmacokinetics and pharmacodynamics of pregabalin and gabapentin. Clin Pharmacokinet. 2010 Oct;49(10):661-9.
  2. Ifuku M, Iseki M, Hidaka I, Morita Y, Komatus S, Inada E. Replacement of gabapentin with pregabalin in postherpetic neuralgia therapy. Pain Med. 2011;12(7):1112-6.
  3. Toth C. Substitution of gabapentin therapy with pregabalin therapy in neuropathic pain due to peripheral neuropathy. Pain Med. 2010;11(3):456-65.