Methadone CBM Flashcards
List 4 common side effects of methadone.
Somnolence/sedation
Respiratory depression
Constipation
Nausea
List 6 rare side effects of methadone.
Depression Hyperglycemia Rashes Peripheral edema Pulmonary edema Pruritus
What are 3 common causes for QT prolongation (not including medications):
Congenital long QT syndromes (suggested by family history of sudden death)
Hypomagnesemia
Hypokalemia
Hypocalcemia
List 6 classes of drugs that can prolong QTc
Antidepressants Antipsychotics Antibiotics Antimalarials Antihistamines Antiarrhythmics
What is the primary enzymatic pathway that metabolizes methadone? What are 2 secondary enzymatic pathways that metabolize methadone?
Primary - CYP 3A4
Secondary - CYP 1A2 and CYP 2D6
Inhibitors of CYP 3A4 (increase methadone levels):
Amiodarone Bicalutamide Clarythromycin Diclofenac Diltiazem Erythromycin Fluconazole Grapefruit juice Haloperidol Irticonazole Imatinib Verapamil
Inhibitors of CYP 3A4 (increase methadone levels):
Amiodarone Bicalutamide Clarythromycin Diclofenac Diltiazem Erythromycin Fluconazole Grapefruit juice Haloperidol Irticonazole Imatinib Verapamil
Inducers of methadone (decrease serum concentration)
Carbamazepine Dexamethasone Modafanil Phenobarbital Phenytoin Rifampicin St. John's Wart
What pharmacologic properties of methadone make it a good analgesic?
NMDA antagonism
Mu agonism
Interacts with a wide selection of known subtypes of opioid receptors
Has effects on serotonin and norepinephrine receptors (similar to SNRIs)
Transformed to inactive metabolites by liver
Eliminated via the bowel
High oral bioavailability
List 6 indications for treatment with methadone:
Opioid tolerance Neuropathic pain Pain in renal failure Inadequate analgesia from other opioids Opioid-induced hyperalgesia Opioid toxicity
List three general methods for switching from a different opioid to methadone:
Stop and Go -
Stepped Switch
Start low, Go slow
The start low, go slow method is bet used for what clinical scenario?
Non urgent rotations done as an outpatient.
The stop and go method is best for what clinical scenario?
Urgent switch needed in a monitored setting (i.e. PCU)
The stepped switch method is best for what type of clinical situation?
Medium urgency of switching to methadone. Semi monitored setting (i.e. daily nurse visits with capable, competent pt/supports).
Describe the start low go slow method of methadone rotation:
Prior opioids continued.
Methadone added in a small dose of 1mg po q8h (or smaller if frail or extremely opioid sensitive).
Pts wait at least 3 days until pain reassessed.
Increase dose of methadone by 100% (i.e. double the dose) and wait another 3 days to r/a effect.
Can use a longer interval if more convenient.
As soon as adequate analgesia achieved, can start reducing prior opioid.
Dose of methadone will need to be increased as prior opioid is cleared.
Use SA opioid for breakthrough pain after the switch.
