What is the recommended protocol for tapering intrathecal (in the spinal canal) baclofen (a muscle relaxant) when transitioning to intrathecal hydromorphone (an opioid analgesic) in a patient?

Transitioning from Intrathecal Baclofen to Intrathecal Hydromorphone

When initiating intrathecal hydromorphone in a patient currently receiving intrathecal baclofen, you must continue the baclofen at its current dose and rate without any taper—abrupt discontinuation of intrathecal baclofen is potentially life-threatening and must be avoided. 1

Critical Safety Principle: Never Taper Intrathecal Baclofen

• Abrupt withdrawal of intrathecal baclofen can cause high fever, altered mental status, rebound spasticity, muscle rigidity leading to rhabdomyolysis, multiorgan failure, and death. 1

• Significant withdrawal symptoms from baclofen include visual and auditory hallucinations, anxiety, agitation, delirium, fever, tremors, tachycardia, and seizures—these symptoms typically evolve over 1-3 days but may become fulminant if not recognized and treated promptly. 1

• The best management strategy for intrathecal baclofen withdrawal is resuming the intrathecal infusion as soon as possible—supportive measures including high-dose benzodiazepine intravenous infusion or oral baclofen may be lifesaving before intrathecal baclofen therapy can be resumed, though acute withdrawal may still occur with high-dose oral baclofen. 1

Recommended Protocol for Dual Intrathecal Therapy

Initial Approach

• Continue intrathecal baclofen at the current dose and rate while initiating intrathecal hydromorphone as a separate medication in the pump. 1

• Modern programmable intrathecal pumps can deliver combination therapy with both baclofen and hydromorphone simultaneously—this is the safest approach and avoids any risk of baclofen withdrawal. 1

• If the pump cannot accommodate both medications, the patient requires urgent consultation with a specialist in intrathecal drug delivery systems and should not have baclofen discontinued. 1

Hydromorphone Initiation Dosing

• For opioid-naïve patients, start intrathecal hydromorphone at extremely low doses (0.05-0.1 mg/day) and titrate upward based on pain relief. 2, 3

• For patients already on systemic opioids, calculate an equianalgesic dose using approximately a 100:1 oral morphine to intrathecal morphine conversion ratio, then convert to hydromorphone using a 5:1 morphine to hydromorphone potency ratio. 3, 4

• Expect that 54% of patients will require dose escalation (median increase of 67%) within the first few days after initiation, particularly younger patients with higher preoperative opioid use. 3

Monitoring Requirements

• Patients must be monitored in a hospital setting for at least 24 hours after initiating intrathecal hydromorphone to assess for respiratory depression, sedation, nausea, pruritus, and urinary retention. 3

• Assess pain levels, sedation scores, and respiratory status every 1-2 hours initially, then every 4 hours once stable. 3

• Continue monitoring for signs of baclofen withdrawal (fever, tachycardia, altered mental status, increased spasticity) throughout the transition period. 1

Common Pitfalls and How to Avoid Them

• Never attempt to taper or discontinue intrathecal baclofen to "make room" for hydromorphone—this is the most dangerous error and can result in death. 1

• Do not assume that oral baclofen can substitute for intrathecal baclofen during a transition—oral baclofen has poor CNS penetration and may not prevent withdrawal syndrome even at high doses. 1

• Avoid underdosing hydromorphone initially out of fear of side effects—96% of patients can discontinue systemic opioids immediately after intrathecal opioid initiation when dosed appropriately, and serious adverse effects are rare with proper conversion ratios. 3

• Do not use fixed conversion ratios without clinical judgment—patients in the highest quartile of dose escalation needs are typically younger, have higher preoperative opioid use, and are inpatients rather than outpatients. 3

Emergency Management of Baclofen Withdrawal

• If baclofen withdrawal occurs despite precautions, immediately restart intrathecal baclofen infusion at the previous dose or higher. 1

• While arranging for intrathecal baclofen resumption, administer high-dose intravenous benzodiazepines (lorazepam 2-4 mg IV every 4-6 hours or midazolam infusion) as a temporizing measure. 1

• Consider high-dose oral baclofen (up to 120 mg/day in divided doses) as an adjunct, though this may not fully prevent withdrawal symptoms. 1

• Intravenous baclofen formulations have been studied and may be considered in emergency situations when intrathecal access cannot be restored immediately—a 20% dose reduction from oral to IV is appropriate given 80% oral bioavailability. 5