Adult Dosing
Pain, moderate to severe
Opioid nontolerant patients
- Start: 2.5-10 mg IV/IM/SC q8-12 hrs, titrate slowly to effect
Opioid tolerant patients
- Conversion from oral methadone to parenteral methadone: follow a 2:1 dose ratio (eg 10 mg oral methadone to 5 mg parenteral methadone)
- Conversion from oral morphine to parenteral methadone: As per the following guidelines
| Total daily baseline ORAL morphine dose | Estimated daily ORAL methadone requirement (% of total daily morphine dose) | Estimated daily IV methadone (% of total daily oral morphine dose) |
|---|
| <100 mg | 20-30% | 10-15% |
| 100-300 mg | 10-20% | 5-10% |
| 300-600 mg | 8-12% | 4-6% |
| 600-1000 mg | 5-10% | 3-5% |
| > 1000 mg | < 5% | < 3% |
- Conversion from parenteral morphine to parenteral methadone for chronic administration: As per the following guidelines
| Total daily baseline Parenteral morphine dose | Estimated daily Parenteral methadone requirement (% of total daily morphine dose) |
|---|
| 10-30 mg | 40-66% |
| 30-50 mg | 27-66% |
| 50-100 mg | 22-50% |
| 100-200 mg | 15-34% |
| 200-500 mg | 10-20% |
Opioid Dependence; detoxification and maintenance treatment
- The patient’s oral methadone dose should be converted to an equivalent parenteral dose using the considerations described above
Notes:
- Particular vigilance is required while converting from other opioids
- Injectable methadone products are not approved for the outpatient treatment of opioid dependence. Parenteral methadone is to be used only for patients unable to take oral medications (such as hospitalized patients)
- Conversion ratios using equianalgesic dosing tables do not apply in the setting of repeated methadone dosing
Pediatric Dosing
- Safety and effectiveness in pediatric patients (<18 years of age) have not been established
[Outline]
- Patients tolerant to other opioids may be incompletely tolerant to methadone; risk of death from cardiac and respiratory causes due to iatrogenic overdosage (US FDA Boxed warning)
- Risk of respiratory depression, QT prolongation and serious arrhythmias including torsades de pointes (US FDA Boxed warning)
- Methadone is less sedating than morphine and acts for longer periods; in long term treatment, it should not be administered more often than bid in order to avoid the risk of accumulation and opioid overdosage
- Severe hypotension may occur in patients whose ability to maintain normal BP is compromised (eg, severe volume depletion)
- Do not use for obstetrical analgesia; risk of neonatal respiratory depression
- Schedule II controlled substance; significant potential for abuse; increased risk of overdose and death
- Taper slowly to discontinue. Physical dependence manifested by withdrawal symptoms and/or seizures may occur after abrupt discontinuation or administration of an antagonist
- May need to decrease dose in patients with hepatic/renal impairment
- A high degree of "opioid tolerance" does not eliminate the possibility of methadone overdose, iatrogenic or otherwise
- Monitor continuously for recurrence of respiratory depression; may need treatment with the narcotic antagonist
- May impair ability to drive or operate machinery
- Monitor Cr at baseline
Cautions: Use cautiously in
Pregnancy Category:C
Breastfeeding: Methadone is excreted in breast milk. When used as maternal maintenance therapy, breastfeeding may decrease neonatal withdrawal symptoms in infants who were exposed in utero. However, as it is excreted in only small amounts, breastfed infants may require treatment for withdrawal. Initiation of methadone postpartum, or increasing the maternal dosage to >100 mg/day therapeutically or by abuse, subjects the infant to a greater risk of sedation and respiratory depression. Monitor infant for signs of increased sedation, breathing difficulties, or limpness. This information is based upon LactMed database (available at http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT). This drug is considered compatible with breastfeeding based upon data from from AAP Policy Guidelines (available at http://aappolicy.aappublications.org/cgi/content/full/pediatrics;108/3/776 last accessed 22 July 2010)
