Methadone Brand Names
Dolophine
(US), Methadone Diskets, Methadone Intensol, Methadose, Metadol (Canadian)
Methadone is
the Generic Name
Methadone
Hydrochloride is belonged to analgesic and opioid pharmacologic category.
Indication / Use
Methadone is
used to manage moderate-to-severe pain. Besides, it is also commonly used for
detoxification and maintenance treatment of opioid addiction. However, it must
be part of an FDA-approved program if it is intended to be used for the latter
purpose.
Restrictions
When
methadone is purposed for treatment of opioid addiction, it may only be
dispensed in accordance to guidelines established by the Substance Abuse and
Mental Health Services Administrations's (SAMHSA) Center for substance Abuse
Treatment (CSAT).
However,
regulations regarding methadone use may vary by state or different country.
Advice should be obtained from appropriate regulatory agencies or consult with
pain management care specialists before dispensing methadone.
There are
regulatory exceptions to the General Requirement to Provide Opioid Agonist
Treatment in which:
1. During
inpatient care, when the patient was admitted for any condition other than
concurrent opioid addiction, with the purpose to facilitate the treatment of
the primary admitting diagnosis.
2. During an
emergency period of no longer than 3 days while definitive care for the
addiction is being sought in an
appropriately licensed facility
Pregnancy Risk Factor Category: C/D (dangerous especially in
prolonged used or at high doses)
Some animal
studies have shown teratogenic effects, however, the data collected by
Teratogen Information System are complicated by other factors including
maternal use of illicit drugs, nutrition supplement, concurrent infections and
psychosocial circumstances.
Though, there
is improvement being observed in pregnant women with methadone treatment
compared to pregnant women using illicit drugs.
Methadone can
be detected in the amniotic fluid, cord plasma, and newborn urine. Fetal
growth, birth weight, length, head or other s may be affected and decreased in
infants born to narcotic-addicted mothers with methadone treatment during
pregnancy. Growth deficits do not appear to persist but decreased performance
on psychometric and behavioural tests has been found to continue into
childhood.
Besides,
there is also report of abnormal fetal nonstress tests where withdrawal
symptoms in the neonate may be observed up to 2-4 weeks after delivery.
Hence,
methadone should be only used during pregnancy when clearly needed where
benefits outweigh risk.
Since
methadone clearance is increased and half-life is decreased during 2nd and 3rd
trimesters of pregnancy, withdrawal symptoms may be observed in the mother and
thus, methadone dosage may need to be increased and adjusted or decreasing
dosing interval during pregnancy.
Methadone may
enter into breast milk and is not recommended to be used during lactation.
Safety issues
Methadone is
always confused with sound or look alike drugs such as dexmethylphenidate or
methylphenidate.
Methadone has
been listed in the drug classes under the Institute for Safe Medication
Practices (ISMP) which may post heightened risk or harm to patient when used in
error.
Contraindications
Respiratory
depression in which in the absence of resuscitative equipment or in an
unmonitored condition, acute bronchial asthma or hypercarbia, paralytic ileus,
concurrent use of selegiline
Precautions
As with other
opioid-containing analgesic regimen, methadone should be tailored to each
patient's needs and based on the type of pain being managed, such as the
factors of acute versus chronic, route of administration, degree of tolerance
for opioids, age, weight, and other medical conditions. Also, the optimal
analgesic dose varies widely among different individuals and methadone doses
should be titrated to pain relief. Patients on stable maintenance doses of
methadone may require higher doses in case of acute pain, for example during
postoperative pain and physical trauma. It is noted that methadone is
ineffective for anxiety relief.
Methadone may
prolong the QT interval and increase risk of torsade de pointes. Before
starting methadone treatment, patients should be informed of the potential
arrhythmia risk, and assessed for history of structural heart disease,
arrhythmia, syncope, or any potential drug interactions including drugs that
prolong QT interval, induce hypokalemia, hypomagnesemia, or hypocalcemia, or
reduce methadone clearance. ECG baseline should be obtained for all patients
and evaluate the risk according to QT interval monitoring.
Methadone must be used iwth caution in patients at risk for QT prolongation, taking medications that would prolong the QT interval, electrolyte depletion inducer or history of conduction abnormalities. Normally QT interval prolongation and torsade de pointes is associated with high doses or greater 100 mg/day, however, it has also been observed with lower doses used.
Methadone may
also cause severe hypotension and should be used cautiously in case of severe volume depletion or
abnormal blood pressure, cardiovascular disease or dysrhythmias.
Methadone may
also cause respiratory depression and care must be taken when used in patinets
with respiratory disease or pre-existing respiratory conditions such as severe
obesity, asthma, COPD, sleep apnea, or CNS depression. Since the respiratory
effects last longer than the analgesic effects, slow titration of methadone
doses is required. Attention and care should be emphasized when initiating
methadone treatment on dose titration and conversion from other opioid
agonists. Incomplete cross tolerance may occur patient may not be tolerant to
methadone even though tolerant to other mu opioid agonists. Abrupt cessation
must be avoided as may precipitate withdrawal symptoms.
Methadone may
cause CNS depression which impair physical or mental abilities and thus should
be cautioned in performing tasks requiring mental alertness such as operating
machinery or driving after taking methadone. Sedative drugs or ethanol may
potentiate methadone effects. Use with caution in patients with depression or
suicidal tendencies or history or drug abuse. Psychological and physical
dependence may occur with prolonged use.
Also, patient with head injury or increased intracranial pressure must be taken extra care. Patients with acute abdominal conditions may obscure diagnosis or clinical course.. Elderly patients is more susceptible to methadone side effects such as CNS, respiratory and gastrointestinal effects and hence, lower initial dose should be used in elderly or debilitated, or in patients with abnormal thyroid metabolism, obesity, adrenal insufficiency, prostatic hyperplasia or urethral stricture and also in impaired renal and hepatic function.
It must be
noted that safety and efficacy of methadone use has not been established in
children.
Methadone Adverse Reactions
Adverse
effects of methadone may decrease over several weeks with prolonged
administration. However, constipation and sweating may persist.
Cardiovascular: arrhythmia, bigeminal rhythms, radycardia, cardiac arrest, cardiomyopathy,
ECG changes, edema, extrasystoles, faintness, flushing, heart failure, hypotension, palpitation, peripheral vasodilation, phlebitis, orthostatic hypotension, QT interval prolonged, shock, syncope, tachycardia, torsade de pointes, T-wave inversion, ventricular fibrillation, ventricular tachycardia
Central nervous system: Agitation, confusion, disorientation, dizziness, drowsiness, dysphoria, euphoria, hallucination, headache, insomnia, light-headedness, sedation, seizure
Dermatologic: Hemorhagic urticaria, pruritus, rash, urticaria (more common when administered intravenously but are rare side effects)
Endocrine & metabolic: Antidiuretic effect, amenorrhea, hypokalemia, hypomagnesemia, decreased libido
Gastrointestinal: Abdominal pain, anorexia, biliary tract spasm, constipation, glossitis, nausea, stomach cramps, vomiting, weight gain, xerostomia
Hematologic: Thrombocytopenia which is reversible, reported in patients with chronic hepatitis
Neuromuscular & skeletal: weakness
Local (intramuscular or subcutaneous injection): Erythema, pain or swelling.
Ocular Miosis, visual disturbances
Respiratory: Pulmonary edema, respiratory depression, respiratory arrest
Miscellaneous: Death, diaphoresis, physical and psychological dependence
Reference:
Charles F.
Lacy, Lora L. Armstrong, Morton P. Goldman, Leonard L.Lance. Drug Information
Handbook 18th Edition. 2009-2010.
Lexi-Comp is the official drug
reference for the American Pharmacists Association.
