Methadone: uses, dosing, side effects & brands

The following serious adverse reactions and/or conditions are described, or described in greater detail, in other sections: • Respiratory Depression [see Warnings and Precautions ( 5.1 )] • Interactions with Benzodiazepines and other CNS Depressants [see Warnings and Precautions ( 5.2 )] • QT Prolongation [see Warnings and Precautions ( 5.3 )] • Serotonin Syndrome [see Warnings and Precautions ( 5.9 )] • Adrenal Insufficiency [see Warnings and Precautions ( 5.10 )] • Severe Hypotension [see Warnings and Precautions ( 5.11 )] • Gastrointestinal Adverse Reactions [see Warnings and Precautions ( 5.13 )] • Seizures [see Warnings and Precautions ( 5.14 )] • Withdrawal [see Warnings and Precautions ( 5.15 )] • Hypoglycemia [see Warnings and Precautions ( 5.17 )] The following adverse reactions have been identified during post-approval use of methadone. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure . The major hazards of methadone are respiratory depression and, to a lesser degree, systemic hypotension. Respiratory arrest, shock, cardiac arrest, and death have occurred. The most frequently observed adverse reactions included lightheadedness, dizziness, sedation, nausea, vomiting, and sweating. These effects seemed to be more…

DISKETS Dispersible Tablets are contraindicated in patients with: • Significant respiratory depression [see Warnings and Precautions ( 5.1 )]. • Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment [see Warnings and Precautions ( 5.8 )]. • Known or suspected gastrointestinal obstruction, including paralytic ileus [see Warnings and Precautions ( 5.13 )]. • Hypersensitivity (e.g. anaphylaxis) to methadone or any other ingredient in DISKETS Dispersible Tablets [see Adverse Reactions ( 6 )]. • Significant respiratory depression ( 4 ) • Acute or severe bronchial asthma ( 4 ) • Known or suspected paralytic ileus ( 4 ) • Known hypersensitivity to methadone ( 4 )

Table 1: Clinically Significant Drug Interactions with DISKETS Dispersible Tablets Benzodiazepines and Other Central Nervous System (CNS) Depressants Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants, including alcohol, increases the risk of respiratory depression, profound sedation, coma, and death. Intervention: Cessation of benzodiazepines or other CNS depressants is preferred in most cases of concomitant use. In some cases, monitoring in a higher level of care for taper may be appropriate. In others, gradually tapering a patient off of a prescribed benzodiazepine or other CNS depressant or decreasing to the lowest effective dose may be appropriate. Before co-prescribing benzodiazepines for anxiety or insomnia, ensure that patients are appropriately diagnosed and consider alternative medications and non-pharmacologic treatments [see Warnings and Precautions ( 5.2 )]. If concomitant use is warranted, strongly consider recommending or prescribing an opioid overdose reversal agent, as is recommended for all patients in treatment for opioid use disorder [see Warnings and Precautions ( 5.1 )]. Examples: Benzodiazepines and other sedatives/hypnotics, anxiolytics, tranquilizers, muscle relaxants, general anesthetics, antipsychotics, gabapentinoids (gabapentin or pregabalin), other opioids, alcohol. Inhibitors of CYP3A4, CYP2B6, CYP2C19, CYP2C9, or CYP2D6 Clinical Impact: Methadone undergoes hepatic N-demethylation by several cytochrome P450 (CYP) isoforms, including CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6. The concomitant use of DISKETS Dispersible Tablets and CYP3A4, CYP2B6, CYP2C19, CYP2C9, or CYP2D6 inhibitors can increase the plasma concentration of methadone, resulting in increased or prolonged opioid effects, and may result in a fatal overdose, particularly when an inhibitor is added after a stable dose of DISKETS Dispersible Tablets is achieved. These effects may be more pronounced with concomitant use of drugs that inhibit more than one of the CYP enzymes listed above. After stopping a CYP3A4, CYP2B6, CYP2C19, CYP2C9, or CYP2D6 inhibitor, as the effects of the inhibitor decline, the methadone plasma concentration can decrease [see Clinical Pharmacology ( 12.3 )] , resulting in decreased opioid efficacy or withdrawal symptoms in patients physically dependent on methadone. Intervention: If concomitant use is necessary, consider dosage reduction of DISKETS Dispersible Tablets until stable drug effects are achieved. Monitor patients for respiratory depression and sedation at frequent intervals. If a CYP3A4, CYP2B6, CYP2C19, CYP2C9, or CYP2D6 inhibitor is discontinued, follow patients for signs of opioid withdrawal and consider increasing the DISKETS Dispersible Tablets dosage until stable drug effects are achieved. Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g. ketoconazole), protease inhibitors (e.g., ritonavir), fluconazole, fluvoxamine, some selective serotonin reuptake inhibitors (SSRIs) (e.g., sertraline, fluvoxamine). Inducers of CYP3A4, CYP2B6, CYP2C19, or CYP2C9 Clinical Impact: The concomitant use of DISKETS Dispersible Tablets and CYP3A4, CYP2B6, CYP2C19, or CYP2C9 inducers can decrease the plasma concentration of methadone [see Clinical Pharmacology ( 12.3 )] , resulting in decreased efficacy or onset of withdrawal symptoms in patients physically dependent on methadone. These effects could be more pronounced with concomitant use of drugs that can induce multiple CYP enzymes. After stopping a CYP3A4, CYP2B6, CYP2C19, or CYP2C9 inducer, as the effects of the inducer decline, the methadone plasma concentration can increase [see Clinical Pharmacology ( 12.3 )] , which could increase or prolong both the therapeutic effects and adverse reactions, and may cause serious respiratory depression, sedation, or death. Intervention: If concomitant use is necessary, consider increasing the DISKETS Dispersible Tablets dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal. If a CYP3A4, CYP2B6, CYP2C19, or CYP2C9 inducer is discontinued, consider DISKETS Dispersible Tablets dosage reduction and monitor for signs of respiratory depression and sedation. Examples: Rifampin, carbamazepine, phenytoin, St. John’s Wort, phenobarbital. Potentially Arrhythmogenic Agents Clinical Impact: Pharmacodynamic interactions may occur with concomitant use of methadone and potentially arrhythmogenic agents or drugs capable of inducing electrolyte disturbances (hypomagnesemia, hypokalemia). Intervention: Monitor patients closely for cardiac conduction changes. Examples: Drugs known to have potential to prolong QT interval: Class I and III antiarrhythmics, some neuroleptics and tricyclic antidepressants, and calcium channel blockers. Drugs capable of inducing electrolyte disturbances: Diuretics, laxatives, and, in rare cases, mineralocorticoid hormones. Serotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome [see Warnings and Precautions ( 5.9 )] . Intervention: If concomitant use is warranted, carefully observe the patient, particularly during treatment initiation and dose adjustment. Discontinue DISKETS if serotonin syndrome is suspected. Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that effect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue). Monoamine Oxidase Inhibitors (MAOIs) Clinical Impact: MAOI interactions with opioids may manifest as serotonin syndrome or opioid toxicity (e.g., respiratory depression, coma) [see Warnings and Precautions ( 5.1 , 5.9 )] . Intervention: The use of DISKETS is not recommended for patients taking MAOIs or within 14 days of stopping such treatment. Examples: Phenelzine, tranylcypromine, linezolid. Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics Clinical Impact: Patients maintained on methadone may experience withdrawal symptoms when given opioid antagonists, mixed agonist/antagonists, and partial agonists. Intervention: Avoid concomitant use. Examples: Butorphanol, nalbuphine, pentazocine, buprenorphine. Muscle Relaxants Clinical Impact: Methadone may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression. Intervention: Monitor patients receiving muscle relaxants and DISKETS Dispersible Tablets for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of the muscle relaxant as necessary. Due to the risk of respiratory depression with concomitant use of skeletal muscle relaxants and opioids, strongly consider recommending or prescribing an opioid overdose reversal agent, as is recommended for all patients in treatment for opioid use disorder [see Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.1 , 5.2 )]. Examples: cyclobenzaprine, metaxalone Diuretics Clinical Impact: Opioids can reduce the efficacy of diuretics by inducing the release of antidiuretic hormone. Intervention: Monitor patients for signs of diminished diuresis and/or effects on blood pressure and increase the dosage of the diuretic as needed. Anticholinergic Drugs Clinical Impact: The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Intervention: Monitor patients for signs of urinary retention or reduced gastric motility when DISKETS are used concomitantly with anticholinergic drugs. Paradoxical Effects of Antiretroviral Agents on Methadone: Concurrent use of certain protease inhibitors with CYP3A4 inhibitory activity, alone and in combination, such as abacavir, amprenavir, darunavir+ritonavir, efavirenz, nelfinavir, nevirapine, ritonavir, telaprevir, lopinavir+ritonavir, saquinavir+ritonavir, and tipranavir+ritonavir, has resulted in increased clearance or decreased plasma levels of methadone. This may result in reduced efficacy of DISKETS Dispersible Tablets and could precipitate a withdrawal syndrome. Monitor patients receiving DISKETS Dispersible Tablets and any of these anti-retroviral therapies closely for evidence of withdrawal effects and adjust the DISKETS Dispersible Tablets dose accordingly. Effects of Methadone on Antiretroviral Agents: Didanosine and Stavudine: Experimental evidence demonstrated that methadone decreased the area under the concentration-time curve (AUC) and peak levels for didanosine and stavudine, with a more significant decrease for didanosine. Methadone disposition was not substantially altered. Zidovudine: Experimental evidence demonstrated that methadone increased the AUC of zidovudine, which could result in toxic effects. Effects of Methadone on Antidepressants: Desipramine: Blood levels of desipramine have increased with concurrent methadone administration. • Potentially Arrhythmogenic Agents: Monitor patients closely for cardiac conduction changes. ( 7 ) • Interactions with CNS Depressants: Consider dose reduction of one or both drugs because of additive effects. ( 7 ) • Mixed Agonist/Antagonist and Partial Agonist Opioids : Avoid concomitant use with DISKETS because it may precipitate withdrawal symptoms. ( 5.15 , 7 )