What is the equivalent dose of Lyrica (pregabalin) for a patient taking gabapentin 600mg orally (PO) three times a day (TID) and do you need to taper the gabapentin dose?

Gabapentin to Pregabalin Conversion and Tapering Protocol

For a patient taking gabapentin 600mg TID (1800mg daily), the equivalent pregabalin dose is 300mg daily (divided as 150mg twice daily), and gabapentin should be gradually tapered while pregabalin is initiated to avoid withdrawal symptoms. 1

Conversion Rationale

Gabapentin 1800mg daily is equivalent to pregabalin 300mg daily based on the following considerations:

• Pregabalin has linear pharmacokinetics and better bioavailability compared to gabapentin's nonlinear pharmacokinetics 1, 2
• Pregabalin 300mg daily is considered therapeutically equivalent to gabapentin 1800mg daily for neuropathic pain 1, 3
• Pregabalin may provide analgesia more quickly than gabapentin because its initial dosage of 150mg daily has been found efficacious in some trials 1

Recommended Conversion Protocol

Week 1:

• Start pregabalin at 75mg twice daily (150mg/day)
• Reduce gabapentin to 600mg twice daily (1200mg/day)

Week 2:

• Increase pregabalin to 150mg twice daily (300mg/day)
• Reduce gabapentin to 600mg once daily (600mg/day)

Week 3:

• Continue pregabalin at 150mg twice daily (300mg/day)
• Discontinue gabapentin

Rationale for Tapering

Gabapentin should be tapered rather than abruptly discontinued for several reasons:

1. The Mayo Clinic guidelines explicitly state: "Treatment should be initiated at low dosages with gradual titration" and "If the gabapentin dose is reduced, discontinued, or substituted with an alternative medication, this should be done gradually over a minimum of 1 week" 1, 4

2. Abrupt discontinuation may lead to withdrawal symptoms including:

   • Anxiety
   • Insomnia
   • Nausea
   • Pain
   • Sweating
   • Potential seizures in patients with epilepsy 4

Dosage Adjustments for Special Populations

Renal Impairment

Both medications require dosage adjustment in renal impairment:

• For pregabalin with creatinine clearance 30-59 mL/min: reduce to 150-300mg/day
• For pregabalin with creatinine clearance 15-29 mL/min: reduce to 75-150mg/day
• For pregabalin with creatinine clearance <15 mL/min: reduce to 25-75mg/day 5

Elderly Patients

• Start with lower doses and titrate more slowly
• Consider starting pregabalin at 50mg twice daily and titrate more gradually 5

Monitoring During Conversion

Monitor for:

• Pain control using a numerical pain rating scale (0-10)
• Adverse effects, particularly dizziness and somnolence (most common with both medications)
• Sleep quality and functional status

Advantages of Pregabalin over Gabapentin

1. Linear pharmacokinetics allowing more predictable dosing 1, 2
2. Twice-daily dosing instead of three times daily, potentially improving adherence 1
3. Faster onset of action with therapeutic effects potentially seen at initial doses 1, 3
4. May provide more consistent pain relief due to more stable blood levels 3

Common Pitfalls to Avoid

1. Abrupt discontinuation: Never stop gabapentin suddenly; always taper to avoid withdrawal symptoms 4
2. Inadequate dose conversion: Underdosing pregabalin may result in breakthrough pain
3. Failure to adjust for renal function: Both medications are primarily eliminated by the kidneys 5, 4
4. Overlooking side effects: Monitor for dizziness and somnolence, which are common with both medications and may be more pronounced during the transition period 1
5. Setting unrealistic expectations: Aim for 30-50% pain reduction rather than complete pain elimination 5

Remember that both medications can cause dose-dependent dizziness and sedation, which can be minimized by starting with lower dosages and titrating cautiously as outlined in the conversion protocol.