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Details with Side Effects
Methadose contains methadone, an opioid agonist and a Schedule II controlled substance. Methadone can be abused in a manner similar to other opioid agonists, legal or illicit. Opioid agonists are sought by drug abusers and people with addiction disorders and are subject to criminal diversion. Consider these risks when prescribing or dispensing Methadose in situations where there is concern about increased risks of misuse, abuse, or diversion. Concerns about abuse, addiction, and diversion should not, however, prevent the proper management of pain.
For each patient prescribed Methadose for pain management, assess the risk for opioid abuse or addiction prior to prescribing Methadose. The risk for opioid abuse is increased in patients with a personal or family history of substance abuse (including drug or alcohol abuse or addiction) or mental illness (e.g., major depression). Patients at increased risk may still be appropriately treated with modified-release opioid formulations; however these patients will require intensive monitoring for signs of misuse, abuse, or addiction. Routinely monitor all patients receiving opioids for signs of misuse, abuse, and addiction because these drugs carry a risk for addiction even under appropriate medical use.
Contact local state professional licensing board or state controlled substances authority for information on how to prevent and detect abuse or diversion of this product.
Life-Threatening Respiratory Depression
Respiratory depression is the primary risk of Methadose. Respiratory depression, if not immediately recognized and treated, may lead to respiratory arrest and death. Respiratory depression from opioids is manifested by a reduced urge to breathe and a decreased rate of respiration, often associated with a “sighing” pattern of breathing (deep breaths separated by abnormally long pauses). Carbon dioxide (CO2) retention from opioid-induced respiratory depression can exacerbate the sedating effects of opioids. Management of respiratory depression may include close observation, supportive measures, and use of opioid antagonists, depending on the patient's clinical status [see OVERDOSAGE].
While serious, life-threatening, or fatal respiratory depression can occur at any time during the use of Methadose, the risk is greatest during the initiation of therapy or following a dose increase. The peak respiratory depressant effect of methadone occurs later, and persists longer than the peak analgesic effect, especially during the initial dosing period. Closely monitor patients for respiratory depression when initiating therapy with Methadose and following dose increases.
Instruct patients against use by individuals other than the patient for whom Methadose was prescribed and to keep Methadose out of the reach of children, as such inappropriate use may result in fatal respiratory depression.
To reduce the risk of respiratory depression, proper dosing and titration of Methadose is essential [see DOSAGE AND ADMINISTRATION]. Overestimating the Methadose dose when converting patients from another opioid product can result in fatal overdose with the first dose. Respiratory depression has also been reported with use of methadone when used as recommended and not misused or abused.
To further reduce the risk of respiratory depression, consider the following:
- Patients tolerant to other opioids may be incompletely tolerant to methadone. Incomplete cross-tolerance is of particular concern for patients tolerant to other mu-opioid agonists who are being converted to treatment with methadone, thus making determination of dosing during opioid treatment conversion complex. Deaths have been reported during conversion from chronic, high-dose treatment with other opioid agonists.
- Proper dosing and titration are essential and Methadose should be prescribed only by healthcare professionals who are knowledgeable in the pharmacokinetics and pharmacodynamics of methadone, especially when converting patients from other opioids, and in the use of potent opioids for the management of chronic pain.
- Methadose is contraindicated in patients with respiratory depression and in patients with conditions that increase the risk of lifethreatening respiratory depression [see CONTRAINDICATIONS].
Life-Threatening QT Prolongation
Cases of QT interval prolongation and serious arrhythmia (torsades de pointes) have been observed during treatment with methadone. These cases appear to be more commonly associated with, but not limited to, higher dose treatment (> 200 mg/day). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In most patients on the lower doses typically used for maintenance, concomitant medications and/or clinical conditions such as hypokalemia were noted as contributing factors. However, the evidence strongly suggests that methadone possesses the potential for adverse cardiac conduction effects in some patients. The effects of methadone on the QT interval have been confirmed in in vivo laboratory studies, and methadone has been shown to inhibit cardiac potassium channels in in vitro studies.
Closely monitor patients with risk factors for development of prolonged QT interval (e.g., cardiac hypertrophy, concomitant diuretic use, hypokalemia, hypomagnesemia), a history of cardiac conduction abnormalities, and those taking medications affecting cardiac conduction. QT prolongation has also been reported in patients with no prior cardiac history who have received high doses of methadone.
Evaluate patients developing QT prolongation while on methadone treatment for the presence of modifiable risk factors, such as concomitant medications with cardiac effects, drugs that might cause electrolyte abnormalities, and drugs that might act as inhibitors of methadone metabolism.
Only initiate Methadose therapy for pain in patients for whom the anticipated benefit outweighs the risk of QT prolongation and development of dysrhythmias that have been reported with high doses of methadone.
The use of methadone in patients already known to have a prolonged QT interval has not been systematically studied.
Accidental ingestion of Methadose, especially in children, can result in a fatal overdose of methadone. Methadone should be kept out of the reach of children to prevent accidental ingestion.
Elderly, Cachectic, and Debilitated Patients
Respiratory depression is more likely to occur in elderly, cachectic, or debilitated patients as they may have altered pharmacokinetics due to poor fat stores, muscle wasting, or altered clearance compared to younger, healthier patients. Therefore, monitor such patients closely, particularly when initiating and titrating Methadose and when Methadose is given concomitantly with other drugs that depress respiration.
Use in Patients with Chronic Pulmonary Disease
Monitor patients with significant chronic obstructive pulmonary disease or cor pulmonale, and patients having a substantially decreased respiratory reserve, hypoxia, hypercapnia, or pre-existing respiratory depression for respiratory depression, particularly when initiating therapy and titrating with Methadose, as in these patients, even usual therapeutic doses of Methadose may decrease respiratory drive to the point of apnea. Consider the use of alternative non-opioid analgesics in these patients if possible.
Interactions with CNS Depressants and Illicit Drugs
Hypotension, profound sedation, coma, or respiratory depression may result if Methadose is used concomitantly with other CNS depressants (e.g., sedatives, anxiolytics, hypnotics, neuroleptics, other opioids). When considering the use of Methadose in a patient taking a CNS depressant, assess the duration of use of the CNS depressant and the patient's response, including the degree of tolerance that has developed to CNS depression. Additionally, consider the patient's use, if any, of alcohol or illicit drugs that cause CNS depression. If Methadose therapy is to be initiated in a patient taking a CNS depressant, start with a lower Methadose dose than usual and monitor patients for signs of sedation and respiratory depression and consider using a lower dose of the concomitant CNS depressant [see DRUG INTERACTIONS].
Deaths associated with illicit use of methadone have frequently involved concomitant benzodiazepine abuse.
Methadose may cause severe hypotension including orthostatic hypotension and syncope in ambulatory patients. There is an increased risk in patients whose ability to maintain blood pressure has already been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (e.g. phenothiazines or general anesthetics) [see DRUG INTERACTIONS]. Monitor these patients for signs of hypotension after initiating or titrating the dose of Methadose.
Use in Patients with Head Injury or Increased Intracranial Pressure
Monitor patients taking Methadose who may be susceptible to the intracranial effects of CO2 retention (e.g., those with evidence of increased intracranial pressure or brain tumors) for signs of sedation and respiratory depression, particularly when initiating therapy with Methadose. Methadose may reduce respiratory drive, and the resultant CO2 retention can further increase intracranial pressure. Opioids may also obscure the clinical course in a patient with a head injury. Avoid the use of Methadose in patients with impaired consciousness or coma.
Use in Patients with Gastrointestinal Conditions
Methadose is contraindicated in patients with paralytic ileus. Avoid the use of Methadose in patients with other gastrointestinal obstruction.
The methadone in Methadose may cause spasm of the sphincter of Oddi. Monitor patients with biliary tract disease, including acute pancreatitis, for worsening symptoms. Opioids may cause increases in the serum amylase.
Use in Patients with Convulsive or Seizure Disorders
The methadone in Methadose may aggravate convulsions in patients with convulsive disorders, and may induce or aggravate seizures in some clinical settings. Monitor patients with a history of seizure disorders for worsened seizure control during Methadose therapy.
Avoidance of Withdrawal
Avoid the use of partial agonists or mixed agonist/antagonist analgesics (i.e., buprenorphine, pentazocine, nalbuphine, and butorphanol) in patients who have received or are receiving a course of therapy with a full opioid agonist analgesic, including Methadose. In these patients, partial agonists or mixed agonists/antagonists analgesics may reduce the analgesic effect and/or may precipitate withdrawal symptoms [see DRUG INTERACTIONS].
When discontinuing Methadose, gradually taper the dose [see DOSAGE AND ADMINISTRATION]. Do not abruptly discontinue Methadose.
Driving and Operating Machinery
Methadose may impair the mental or physical abilities needed to perform potentially hazardous activities such as driving a car or operating machinery. Warn patients not to drive or operate dangerous machinery unless they are tolerant to the effects of Methadose and know how they will react to the medication.
Patient Counseling Information
See FDA-approved patient labeling (Medication Guide)
Inform patients that Methadose contains methadone, a Schedule II controlled substance that is subject to abuse. Instruct patients not to share Methadose with others and to take steps to protect Methadose from theft or misuse.
Life-Threatening Respiratory Depression Discuss the risk of respiratory depression with patients, explaining that the risk is greatest when starting Methadose or when the dose is increased. Advise patients how to recognize respiratory depression and to seek medical attention if they are experiencing breathing difficulties.
Symptoms of Arrhythmia
Instruct patients to seek medical attention immediately if they experience symptoms suggestive of an arrhythmia (such as palpitations, near syncope, or syncope) when taking methadone.
Instruct patients to take steps to store Methadose securely. Accidental exposure, especially in children, may result in serious harm or death. Advise patients to dispose of unused Methadose by flushing the tablets down the toilet.
Risks from Concomitant Use of Alcohol and other CNS Depressants
Inform patients that the concomitant use of alcohol with Methadose can increase the risk of life-threatening respiratory depression. Instruct patients not to consume alcoholic beverages, as well as prescription and over-the-counter drug products that contain alcohol, during treatment with Methadose.
Inform patients that potentially serious additive effects may occur if Methadose is used with other CNS depressants, and not to use such drugs unless supervised by a healthcare provider.
Important Administration Instructions
Instruct patients how to properly take Methadose, including the following:
- Using Methadose exactly as prescribed to reduce the risk of life-threatening adverse reactions (e.g., respiratory depression)
- Not discontinuing Methadose without first discussing the need for a tapering regimen with the prescriber
Inform patients that Methadose may cause orthostatic hypotension and syncope. Instruct patients how to recognize symptoms of low blood pressure and how to reduce the risk of serious consequences should hypotension occur (e.g., sit or lie down, carefully rise from a sitting or lying position).
Driving or Operating Heavy Machinery
Inform patients that Methadose may impair the ability to perform potentially hazardous activities such as driving a car or operating heavy machinery. Advise patients not to perform such tasks until they know how they will react to the medication.
Advise patients of the potential for severe constipation, including management instructions and when to seek medical attention.
Inform patients that anaphylaxis has been reported with ingredients contained in Methadose. Advise patients how to recognize such a reaction and when to seek medical attention.
Advise female patients that Methadose can cause fetal harm and to inform the prescriber if they are pregnant or plan to become pregnant.
Instruct nursing mothers using Methadose to watch for signs of methadone toxicity in their infants, which include increased sleepiness (more than usual), difficulty breastfeeding, breathing difficulties, or limpness. Instruct nursing mothers to talk to the baby's healthcare provider immediately if they notice these signs. If they cannot reach the healthcare provider right away, instruct them to take the baby to the emergency room or call 911 (or local emergency services).
Carcinogenesis, Mutagenesis, Impairment of Fertility
The results of carcinogenicity assessment in B6C2F1 mice and Fischer 344 rats following dietary administration of two doses of methadone HCl have been published. Mice consumed 15 mg/kg/day or 60 mg/kg/day methadone for two years. These doses were approximately 0.6 and 2.5 times a human daily oral dose of 120 mg/day on a body surface area basis (mg/m²). There was a significant increase in pituitary adenomas in female mice treated with 15 mg/kg/day but not with 60 mg/kg/day. Under the conditions of the assay, there was no clear evidence for a treatment-related increase in the incidence of neoplasms in male rats. Due to decreased food consumption in males at the high dose, male rats consumed 16 mg/kg/day and 28 mg/kg/day of methadone for two years. These doses were approximately 1.3 and 2.3 times a human daily oral dose of 120 mg/day, based on body surface area comparison. In contrast, female rats consumed 46 mg/kg/day or 88 mg/kg/day for two years. These doses were approximately 3.7 and 7.1 times a human daily oral dose of 120 mg/day, based on body surface area comparison. Under the conditions of the assay, there was no clear evidence for a treatment-related increase in the incidence of neoplasms in either male or female rats.
There are several published reports on the potential genetic toxicity of methadone. Methadone tested positive in the in vivo mouse dominant lethal assay and the in vivo mammalian spermatogonial chromosome aberration test. Additionally, methadone tested positive in the E. coli DNA repair system and Neurospora crassa and mouse lymphoma forward mutation assays. In contrast, methadone tested negative in tests for chromosome breakage and disjunction and sex-linked recessive lethal gene mutations in germ cells of Drosophila using feeding and injection procedures.
Published animal studies show that methadone treatment of males can alter reproductive function. Methadone produces a significant regression of sex accessory organs and testes of male mice and rats.
Use In Specific Populations
Pregnancy Category C
There are no adequate and well controlled studies of methadone use in pregnant women. Methadone has been shown to be teratogenic in the hamster at doses 2 times the human daily oral dose (120 mg/day on a mg/m² basis) and in mice at doses equivalent to the human daily oral dose (120 mg/day on a mg/m² basis). Increased neonatal mortality and significant differences in behavioral tests have been reported in the offspring of male rodents that were treated with methadone prior to mating when compared to control animals. Methadone has been detected in human amniotic fluid and cord plasma at concentrations proportional to maternal plasma and in newborn urine at lower concentrations than corresponding maternal urine. Methadone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Dosage Adjustment during Pregnancy
The disposition of oral methadone has been studied in approximately 30 pregnant patients in 2nd and 3rd trimesters. Total body clearance of methadone was increased in pregnant patients compared to the same patients postpartum or to non-pregnant opioiddependent women. The terminal half-life of methadone is decreased during 2nd and 3rd trimesters. The decrease in plasma half-life and increased clearance of methadone resulting in lower methadone trough levels during pregnancy can lead to withdrawal symptoms in some pregnant patients. The dosage may need to be increased or the dosing interval decreased in pregnant patients receiving methadone to achieve therapeutic effect [see DOSAGE AND ADMINISTRATION].
Effects on the Neonate
Babies born to mothers who have been taking opioids regularly prior to delivery may be physically dependent. Onset of withdrawal symptoms in infants is usually in the first days after birth. Monitor newborn for withdrawal signs and symptoms including: irritability and excessive crying, tremors, hyper-active reflexes, increased respiratory rate, increased stools, sneezing, yawning, vomiting, and fever. The intensity of the neonatal withdrawal syndrome does not always correlate with the maternal dose or the duration of maternal exposure. The duration of the withdrawal signs may vary from a few days to weeks or even months. There is no consensus on the appropriate management of infant withdrawal [see Use In Specific Populations].
Reported studies have generally compared the benefit of methadone to the risk of untreated addiction to illicit drugs; the relevance of these findings to pain patients prescribed methadone during pregnancy is unclear. Pregnant women involved in methadone maintenance programs have been reported to have significantly improved prenatal care leading to significantly reduced incidence of obstetric and fetal complications and neonatal morbidity and mortality when compared to women using illicit drugs. Several factors, including maternal use of illicit drugs, nutrition, infection and psychosocial circumstances, complicate the interpretation of investigations of the children of women who take methadone during pregnancy. Information is limited regarding dose and duration of methadone use during pregnancy, and most maternal exposure appears to occur after the first trimester of pregnancy. A review of published data on experiences with methadone use during pregnancy by the Teratogen Information System (TERIS) concluded that maternal use of methadone during pregnancy as part of a supervised, therapeutic regimen is unlikely to pose a substantial teratogenic risk (quantity and quality of data assessed as “limited to fair”). However, the data are insufficient to state that there is no risk (TERIS, last reviewed October, 2002). A retrospective case series of 101 pregnant, opioid-dependent women who underwent inpatient opioid detoxification with methadone did not demonstrate any increased risk of miscarriage in the 2nd trimester or premature delivery in the 3rd trimester. Recent studies suggest an increased risk of premature delivery in opioid-dependent women exposed to methadone during pregnancy, although the presence of confounding factors makes it difficult to determine a causal relationship. Several studies have suggested that infants born to narcotic-addicted women treated with methadone during all or part of pregnancy have been found to have decreased fetal growth with reduced birth weight, length, and/or head circumference compared to controls. This growth deficit does not appear to persist into later childhood. Children prenatally exposed to methadone have been reported to demonstrate mild but persistent deficits in performance on psychometric and behavioral tests. In addition, several studies suggest that children born to opioid-dependent women exposed to methadone during pregnancy may have an increased risk of visual development anomalies; however, a causal relationship has not been assigned.
There are conflicting reports on whether Sudden Infant Death Syndrome occurs with an increased incidence in infants born to women treated with methadone during pregnancy. Abnormal fetal non-stress tests have been reported to occur more frequently when the test is performed 1 to 2 hours after a maintenance dose of methadone in late pregnancy compared to controls.
Methadone did not produce teratogenic effects in rat or rabbit models. Methadone produced teratogenic effects following large doses, in the guinea pig, hamster and mouse. One published study in pregnant hamsters indicated that a single subcutaneous dose of methadone ranging from 31 to 185 mg/kg (the 31 mg/kg dose is approximately 2 times a human daily oral dose of 120 mg/day on a mg/m² basis) on day 8 of gestation resulted in a decrease in the number of fetuses per litter and an increase in the percentage of fetuses exhibiting congenital malformations described as exencephaly, cranioschisis, and “various other lesions.” The majority of the doses tested also resulted in maternal death. In another study, a single subcutaneous dose of 22 to 24 mg/kg methadone (estimated exposure was approximately equivalent to a human daily oral dose of 120 mg/day on a mg/m² basis) administered on day 9 of gestation in mice also produced exencephaly in 11% of the embryos. However, no effects were reported in rats and rabbits at oral doses up to 40 mg/kg (estimated exposure was approximately 3 and 6 times, respectively, a human daily oral dose of 120 mg/day on a mg/m² basis) administered during days 6 to 15 and 6 to 18, respectively.
Published animal data have reported increased neonatal mortality in the offspring of male rodents that were treated with methadone prior to mating. In these studies, the female rodents were not treated with methadone, indicating paternally-mediated developmental toxicity. Specifically, methadone administered to the male rat prior to mating with methadone-na´ve females resulted in decreased weight gain in progeny after weaning. The male progeny demonstrated reduced thymus weights, whereas the female progeny demonstrated increased adrenal weights. Behavioral testing of these male and female progeny revealed significant differences in behavioral tests compared to control animals, suggesting that paternal methadone exposure can produce physiological and behavioral changes in progeny in this model. Other animal studies have reported that perinatal exposure to opioids including methadone alters neuronal development and behavior in the offspring. Perinatal methadone exposure in rats has been linked to alterations in learning ability, motor activity, thermal regulation, nociceptive responses and sensitivity to drugs.
Additional animal data demonstrates evidence for neurochemical changes in the brains of methadone-treated offspring, including changes to the cholinergic, dopaminergic, noradrenergic and serotonergic systems. Studies demonstrated that methadone treatment of male rats for 21 to 32 days prior to mating with methadone-na´ve females did not produce any adverse effects, suggesting that prolonged methadone treatment of the male rat resulted in tolerance to the developmental toxicities noted in the progeny. Mechanistic studies in this rat model suggest that the developmental effects of “paternal” methadone on the progeny appear to be due to decreased testosterone production. These animal data mirror the reported clinical findings of decreased testosterone levels in human males on methadone maintenance therapy for opioid addiction and in males receiving chronic intraspinal opioids.
Additional data have been published indicating that methadone treatment of male rats (once a day for three consecutive days) increased embryolethality and neonatal mortality. Examination of uterine contents of methadone-na´ve female mice bred to methadone-treated mice indicated that methadone treatment produced an increase in the rate of preimplantation deaths in all postmeiotic states.
Labor and Delivery
Methadose is not for use in women during and immediately prior to labor, where shorter acting analgesics or other analgesic techniques are more appropriate [see INDICATIONS AND USAGE]. Opioid analgesics may prolong labor by temporarily reducing the strength, duration and frequency of uterine contractions. However, these effects are not consistent and may be offset by an increased rate of cervical dilatation, which tends to shorten labor.
Opioids with mixed agonist-antagonist properties should not be used for pain control during labor in patients chronically treated with methadone as they may precipitate acute withdrawal [see DRUG INTERACTIONS].
Opioids cross the placenta and may produce respiratory depression and psycho-physiologic effects in neonates. Closely observe neonates whose mothers received opioid analgesics during labor for signs of respiratory depression. An opioid antagonist, such as naloxone, should be available for reversal of opioid-induced respiratory depression in the neonate.
Methadone is secreted into human milk. At maternal oral doses of 10 to 80 mg/day, methadone concentrations from 50 to 570 mcg/L in milk have been reported, which, in the majority of samples, were lower than maternal serum drug concentrations at steady state. Peak methadone levels in milk occur approximately 4 to 5 hours after an oral dose. Based on an average milk consumption of 150 mL/kg/day, an infant would consume approximately 17.4 mcg/kg/day which is approximately 2 to 3% of the oral maternal dose. Methadone has been detected in very low plasma concentrations in some infants whose mothers were taking methadone. Cases of sedation and respiratory depression in infants exposed to methadone through breast milk have been reported. Caution should be exercised when methadone is administered to a nursing woman.
Advise women who are being treated with methadone and who are breastfeeding or express a desire to breastfeed of the presence of methadone in human milk. Instruct breastfeeding mothers how to identify respiratory depression and sedation in their babies and when it may be necessary to contact their healthcare provider or seek immediate medical care. Breastfed infants of mothers using methadone should be weaned gradually to prevent development of withdrawal symptoms in the infant.
The safety, effectiveness, and pharmacokinetics of methadone in pediatric patients below the age of 18 years have not been established.
Clinical studies of methadone did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently compared to younger subjects. Other reported clinical experience has not identified differences in responses between elderly and younger patients. In general, start elderly patients at the low end of the dosing range, taking into account the greater frequency of decreased hepatic, renal, or cardiac function and of concomitant disease or other drug therapy in geriatric patients. Closely monitor elderly patients for signs of respiratory and central nervous system depression.
Neonatal Opioid Withdrawal Syndrome
Chronic maternal use of methadone during pregnancy can affect the fetus with subsequent withdrawal signs. Neonatal withdrawal syndrome presents as irritability, hyperactivity and abnormal sleep pattern, high pitched cry, tremor, vomiting, diarrhea and failure to gain weight. The onset, duration and severity of neonatal withdrawal syndrome vary based on the drug used, duration of use, the dose of last maternal use, and rate of elimination drug by the newborn. Neonatal opioid withdrawal syndrome, unlike opioid withdrawal syndrome in adults, may be life-threatening and should be treated according to protocols developed by neonatology experts.
Methadone pharmacokinetics have not been extensively evaluated in patients with renal insufficiency. Since unmetabolized methadone and its metabolites are excreted in urine to a variable degree, start these patients on lower doses and with longer dosing intervals and titrate slowly while carefully monitoring for signs of respiratory and central nervous system depression.
Methadone has not been extensively evaluated in patients with hepatic insufficiency. Methadone is metabolized by hepatic pathways; therefore, patients with liver impairment may be at risk of increased systemic exposure to methadone after multiple dosing. Start these patients on lower doses and titrate slowly while carefully monitoring for signs of respiratory and central nervous system depression.
Last reviewed on RxList: 8/1/2012
This monograph has been modified to include the generic and brand name in many instances.
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