Parenteral Manual

Methadone (SPECIAL ACCESS PROGRAM)

Disclaimer: Official controlled document is the CHEO online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Alternate Name(s): 
Dolophine, Metadol
Classification: 
Analgesic, Narcotic
Original Date: 
December 2022
Indications: 
  • Management of moderate to severe pain unresponsive to non-opioids or as an alternative to  standard intravenous opioids 
  • Parenteral methadone should only be used for patients unable to take oral formulation 
Reconstitution and Stability: 
  • Available as a 10 mg/mL solution, stable at room temperature, protect from light 
Compatibility: 
  • Solution compatible: 0.9% NaCl 
  • Y-site Compatible:  dexamethasone, diazepam, diphenhydramine, haloperidol, lorazepam, methotrimeprazine, metoclopramide, midazolam 
  • Incompatible: furosemide, phenytoin, sodium bicarbonate 
Administration: 

(For approved routes of administration by nursing personnel, refer to Policy for the Administration of Intravenous Medications.)

SC YES (bolus or continuous infusion)
IM YES
IV Direct NO
IV Intermittent Infusion

YES

  • Can be administered undiluted or if more volume required, can be further diluted to 1 mg/mL with 0.9% NaCl prior to administration
  • Infusion time: over 10 minutes
IV Continuous Infusion Yes

 

Dosage: 

(For neonatal dosages, refer to Neonatal IV Drug Manual.)

  • Initial: 0.1 mg/kg/dose  q4h x 2-3 doses then every 6-12 hours as needed (max initial dose 10 mg/dose)
  • Conversion from oral to parenteral route (SC, IM, IV):   
    • Option 1: Administer 50% of total oral daily dose into 3 equal doses given Q8h.  Breakthrough doses equivalent to 10% of total daily doses should also be prescribed q2h prn   
    • Option 2: administer 50% of total oral daily dose as a continuous IV or SC infusion over 24 hours.  Breakthrough doses equivalent to ½ the hourly dose should also be prescribed Q1H prn 
    • Using oral: parenteral ratio of 2:1 is conservative considering the oral bioavailabilty of methadone equals 80%.  However, there is high inter-patient variability in absorption, metabolism and relative analgesic potency making conversion ratios not accurate.  
Potential hazards of parenteral administration: 
  • Cardiovascular: Obtain ECG prior and during therapy (may cause QTc  interval prolongation and serious arrhythmia) 
  • Monitor for respiratory depression especially within the first 72 hours of initiating therapy and following dosages increases 
  • Local tissue irritation may occur with subcutaneous administration 
  • Overdoses may be reversed with naloxone but as half-life of methadone is very long, a continuous infusion may be required 
Notes: 
  • Injectable methadone is not marketed in Canada and falls under the jurisdiction of the Special Access Program (SAP) 
  • Co-administration of methadone with other drugs may result in variable serum levels.  Refer to available references or clinical pharmacist for dosage adjustment 
  • Methadone is liver metabolized and dose should be decreased in severe liver failure 

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