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Question (08/14/2013):

Title: Is there a formula for calculating the intrathecal doses of morphine and baclofen to oral?

I have MS and in 2006 I had a Medtronic SynchroMed II intrathecal Morphine/Baclofen pump placed.

My pump management dr decided to take a 2 month trip to South Africa right before my battery went out.

I was receiving 5.4 mgs/day of morphine and 157.4 mcgs/day of baclofen.

Is there a formula for calculating the intrathecal doses to oral?

Answer:

Thank you very much for your question.

Morphine Dosage : Usual Adult Dose for Pain:

Oral, Sublingual, or Buccal: 5 to 30 mg every 3 to 4 hours as needed

Intrathecal: 0.2 to 1 mg one time

Intrathecal Continuous: 0.2 mg/24 hours. May be increased up to 20 mg/24 hours

The conversion challenge: from intrathecal to oral morphine.

Sylvester RK, Lindsay SM, Schauer C.

Source: MeritCare Hospital, Fargo, North Dakota, USA.

Abstract:

Numerous articles have described the methodologies used and outcomes achieved with the intrathecal (IT) administration of morphine for pain. However, only one case report has been published that describes converting a patient's IT morphine to an oral regimen. This case report describes the experience of converting a patient's IT morphine to oral morphine and discusses the scarcity of published data to validate suggested equianalgesic intraspinal morphine recommendations. The calculated equianalgesic oral to IT ratio in this case was 12:1. This is substantially lower than the 300:1 ratio published by Krames and the 90:1 ratio employed by a commercially available software program for calculating equianalgesic opioid doses. We recommend caution when applying existing guidelines for conversion of morphine from an IT to an oral regimen.

When baclofen is administered orally, only a small portion of the original dose crosses the blood brain barrier and enters the central nervous system (CNS) fluid, which is the site of drug action. In order to bypass the oral route, baclofen may be administered intrathecally by infusion directly to the CNS.

Usual Adult Dose of Baclofen for Trigeminal Neuralgia:

Oral: Initial dose: 5 mg orally 3 times a day for 3 days, then 10 mg orally 3 times a day for 3 days, then 15 mg orally 3 times a day for 3 days, then 20 mg orally 3 times a day.

Maintenance dose: 40-80 mg/day.

80 mg/day doses should be administered in 4 divided doses.

Intrathecal: Test dose: 50 mcg (in a volume of 1 mL) injected into the intrathecal space by barbotage over at least 1 minute. Observe patient for 4-8 hours for a positive response.

Second test dose: If no positive response to first test dose, 75 mcg (in a volume of 1.5 mL) may be administered 24 hours later.

Third test dose: If no positive response to second test dose, 100 mcg (in a volume of 2 mL) may be administered 24 hours later. If no positive response to third test dose, the patient should not be considered for chronic intrathecal therapy.

The test dose that received a positive response should be doubled and given over 24 hours. If the test dose maintained a positive response for > 12 hours, the starting daily dose should be the same as the effective test dose. After 24 hours, the dose may be titrated by 10%-20% increments every day until the desired clinical effect is achieved. Over time, many patients will require gradual dose increases to maintain the desired clinical effect. Patients have been maintained on daily doses of 12-1500 mcg. Most patients require 300-800 mcg/day.

Usual Adult Dose of Baclofen for Hiccups:

Initial dose: 5 mg orally 3 times a day for 3 days, then 10 mg orally 3 times a day for 3 days, then 15 mg orally 3 times a day for 3 days, then 20 mg orally 3 times a day.

Maintenance dose: 40-80 mg/day.

80 mg/day doses should be administered in 4 divided doses.

Usual Adult Dose of Baclofen for Cerebral Spasticity:

Intrathecal: Test dose: 50 mcg (in a volume of 1 mL) injected into the intrathecal space by barbotage over at least 1 minute. Observe patient for 4-8 hours for a positive response.

Second test dose: If no positive response to first test dose, 75 mcg (in a volume of 1.5 mL) may be administered 24 hours later.

Third test dose: If no positive response to second test dose, 100 mcg (in a volume of 2 mL) may be administered 24 hours later. If no positive response to third test dose, the patient should not be considered for chronic intrathecal therapy.

If a positive response has occurred following a test dose, an intrathecal infusion device may be surgically implanted.

The test dose that received a positive response should be doubled and given over 24 hours. If the test dose maintained a positive response for > 12 hours, the starting daily dose should be the same as the effective test dose. After 24 hours, the dose may be titrated by 10%-20% increments every day until the desired clinical effect is achieved. Over time, many patients will require gradual dose increases to maintain the desired clinical effect. Patients have been maintained on daily doses of 12-1500 mcg. Most patients require 300-800 mcg/day.


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