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Methadone
Overview
What is Methadone?
Methadone Hydrochloride Injection, USP, 10 mg/mL is an opioid analgesic.
Each milliliter of Methadone Hydrochloride Injection contains 10 mg (0.029 mmol) of methadone hydrochloride, equivalent to 8.95 mg of methadone free base.
Methadone hydrochloride is a white, crystalline material that is water-soluble.
Methadone hydrochloride is chemically described as 6-(dimethylamino)-4,4-diphenyl-3-hepatanone hydrochloride. Its molecular formula is CHNO•HCl and it has a molecular weight of 345.91. Methadone hydrochloride has a melting point of 235° C, and a pKa of 8.25 in water at 20°C. Its octanol/water partition coefficient at pH 7.4 is 117. A solution (1:100) in water has a pH between 4.5 and 6.5.
It has the following structural formula:
Methadone Hydrochloride Injection is a sterile injectable solution containing the following inactive ingredients: chlorobutanol, 0.5%, as a preservative, and sodium chloride. The pH of the sterile injectable solution may have been adjusted during manufacturing with sodium hydroxide and/or hydrochloric acid.
What does Methadone look like?
What are the available doses of Methadone?
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What should I talk to my health care provider before I take Methadone?
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How should I use Methadone?
Outpatient maintenance and outpatient detoxification treatment may be provided only by opioid treatment programs (OTPs) certified by the Federal Substance Abuse and Mental Health Services Administration (SAMHSA) and registered by the Drug Enforcement Administration (DEA). This does not preclude the maintenance treatment of a patient with concurrent opioid addiction who is hospitalized for conditions other than opioid addiction and who requires temporary maintenance during the critical period of hospitalization, or of a patient whose enrollment has been verified in a program which has been certified for maintenance treatment with methadone.
Methadone differs from many other opioid agonists in several important ways. Methadone's pharmacokinetic properties, coupled with high interpatient variability in its absorption, metabolism, and relative analgesic potency, necessitate a cautious and highly individualized approach to prescribing. Particular vigilance is necessary during treatment initiation, during conversion from one opioid to another, and during dose titration.
While methadone's duration of analgesic action (typically 4 to 8 hours) in the setting of single-dose studies approximates that of morphine, methadone's plasma elimination half-life is substantially longer than that of morphine (typically 8 to 59 hours vs. 1 to 5 hours). Methadone's peak respiratory depressant effects typically occur later, and persist longer than its peak analgesic effects. Also, with repeated dosing, methadone may be retained in the liver and then slowly released, prolonging the duration of action despite low plasma concentrations. For these reasons, steady-state plasma concentrations, and full analgesic effects, are usually not attained until 3 to 5 days of dosing. Additionally, incomplete cross-tolerance between μ-opioid agonists makes determination of dosing during opioid conversion complex.
All of these characteristics make methadone dosing complex and can contribute to cases of iatrogenic overdose, particularly during treatment initiation and dose titration.
What interacts with Methadone?
Methadone Hydrochloride Injection is contraindicated in patients with a known hypersensitivity to methadone hydrochloride or any other ingredient in Methadone Hydrochloride Injection. Methadone Hydrochloride Injection is contraindicated in any situation where opioids are contraindicated such as: patients with respiratory depression (in the absence of resuscitative equipment or in unmonitored settings), and in patients with acute bronchial asthma or hypercarbia.
What are the warnings of Methadone?
Cardiac Conduction Effects
Laboratory studies, both and , have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. 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.
Methadone should be administered with particular caution to patients already at risk for development of prolonged QT interval (e.g., cardiac hypertrophy, concomitant diuretic use, hypokalemia, hypomagnesemia). Careful monitoring is recommended when using methadone in patients with a history of cardiac conduction abnormalities, those taking medications affecting cardiac conduction, and in other cases where history or physical exam suggest an increased risk of dysrhythmia. QT prolongation has also been reported in patients with no prior cardiac history who have received high doses of methadone. Patients developing QT prolongation while on methadone treatment should be evaluated for the presence of modifiable risk factors, such as concomitant medications with cardiac effects, drugs which might cause electrolyte abnormalities, and drugs which might act as inhibitors of methadone metabolism. For use of methadone to treat pain, the risk of QT prolongation and development of dysrhythmias should be weighed against the benefit of adequate pain management and the availability of alternative therapies.
Methadone treatment for analgesic therapy in patients with acute or chronic pain should only be initiated if the potential analgesic or palliative care benefit of treatment with methadone has been considered to outweigh the risk of QT prolongation that has 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.
In using methadone an individualized benefit to risk assessment should be carried out and should include evaluation of patient presentation and complete medical history. For patients judged to be at risk, careful monitoring of cardiovascular status, including QT prolongation and dysrhythmias and those described previously should be performed.
Respiratory Depression
Respiratory depression is the chief hazard from methadone hydrochloride. Respiratory depression is a particular potential problem in elderly or debilitated patients as well as in those suffering from conditions accompanied by hypoxia or hypercapnia when even moderate therapeutic doses may dangerously decrease pulmonary ventilation.
Methadone Hydrochloride Injection should be administered with extreme caution to patients with conditions accompanied by hypoxia, hypercapnia, or decreased respiratory reserve such as; asthma, chronic obstructive pulmonary disease or cor pulmonale, severe obesity, sleep apnea syndrome, myxedema, kyphoscoliosis, CNS depression or coma. In these patients even usual therapeutic doses of methadone may decrease respiratory drive while simultaneously increasing airway resistance to the point of apnea. Alternative non-opioid analgesics should be considered, and methadone should be employed only under careful medical supervision at the lowest effective dose.
Methadone's peak respiratory depressant effects typically occur later, and persist longer than its peak analgesic effects, in the short-term use setting. These characteristics can contribute to cases of iatrogenic overdose, particularly during treatment initiation and dose titration.
Incomplete Cross-Tolerance Between Methadone and Other Opioids
Patients tolerant to other opioids may be incompletely tolerant to methadone. Incomplete cross-tolerance is a particular concern for patients tolerant to other μ-opioid agonists when converting to methadone, making determination of dosing during opioid conversion complex. Deaths have been reported during conversion from chronic, high dose treatment with other opioid agonists. Therefore, it is critical to understand the pharmacokinetics of methadone when converting patients from other opioids (see , and , for appropriate conversion schedules). A high degree of "opioid tolerance" does not eliminate the possibility of methadone toxicity.
Misuse, Abuse, and Diversion of Opioids
Methadone is a μ-agonist opioid with an abuse liability similar to that of morphine and is a Schedule II controlled substance. Methadone, like morphine and other opioids used for analgesia, has the potential for being abused and is subject to criminal diversion.
Methadone can be abused in a manner similar to other opioid agonists, legal or illicit. This should be considered when dispensing Methadone Hydrochloride Injection in situations where the clinician is concerned about an increased risk of misuse, abuse, or diversion.
Concerns about abuse, addiction, diversion should not prevent the proper management of pain.
Healthcare professionals should contact their State Professional Licensing Board, or State Controlled Substances Authority for information on how to prevent and detect abuse or diversion of this product.
Interactions with other CNS Depressants
Patients receiving other opioid analgesics, general anesthetics, phenothiazines, other tranquilizers, sedatives, hypnotics, or other CNS depressants (including alcohol) concomitantly with methadone may experience respiratory depression, hypotension, profound sedation, or coma (see )
Interactions with Alcohol and Drugs of Abuse
Methadone may be expected to have additive effects when used in conjunction with alcohol, other opioids, or illicit drugs that cause central nervous system depression. Deaths associated with illicit use of methadone have frequently involved concomitant benzodiazepine abuse.
Head Injury and Increased Intracranial Pressure
The respiratory depressant effects of opioids and their capacity to elevate cerebrospinal-fluid pressure may be markedly exaggerated in the presence of head injury, other intracranial lesions or a pre-existing increase in intracranial pressure. Furthermore, opioids produce effects which may obscure the clinical course of patients with head injuries. In such patients, opioids must be used with caution, and only if it is deemed essential.
Acute Abdominal Conditions
The administration of opioids may obscure the diagnosis of clinical course of patients with acute abdominal conditions.
Hypotensive Effect
The administration of methadone may result in severe hypotension in patients whose ability to maintain normal blood pressure is compromised (i.e., severe volume depletion).
What are the precautions of Methadone?
General
Methadone given on a fixed-dose schedule may have a narrow therapeutic index in certain patient populations, especially when combined with other drugs, and should be reserved for cases where the benefits of opioid analgesia outweigh the known potential risks of cardiac conduction abnormalities, respiratory depression, altered mental states and postural hypotension. Methadone Hydrochloride Injection should be used with caution in elderly and debilitated patients; patients who are known to be sensitive to central nervous system depressants, such as those with cardiovascular, pulmonary, renal, or hepatic disease; and in patients with comorbid conditions or concomitant medications which may predispose to dysrhythmia.
Selection of patients for treatment with methadone should be governed by the same principles that apply to the use of other parenteral opioids (see ). Physicians should individualize treatment in every case (see ), taking into account the high degree of interpatient variability in response to and metabolism of methadone.
Drug Interactions
In vitro
Opioid antagonists, mixed agonist/antagonists, and partial agonists:
Cytochrome P450 inhibitors:
Potentially Arrhythmogenic Agents:
Interactions with other CNS Depressants:
Use with Mixed Agonist/Antagonist Opioid Analgesics:
Anxiety
Methadone, used by tolerant patients at a constant maintenance dosage, is not a tranquilizer. Patients who are maintained on this drug will react to life problems and stresses as do other individuals. Anxiety in a patient on methadone should not be confused with narcotic abstinence and should not prompt treatment by increasing the dosage of methadone. The action of methadone in maintenance treatment is limited to the control of symptoms of opioid dependence or pain. Methadone is ineffective for relief of general anxiety.
Acute Pain
Maintenance patients on a stable dose of methadone who experience physical trauma, postoperative pain or other causes of acute pain cannot be expected to derive analgesia from their stable dose of methadone regimens. Such patients should be given analgesics, including opioids, that would be indicated in other patients experiencing similar nociceptive stimulation. Due to the opioid tolerance induced by methadone, when opioids are required for management of acute pain in methadone patients, somewhat higher and/or more frequent doses will often be required than would be the case for other, non-tolerant patients.
Risk of Relapse in Patients on Methadone Maintenance Treatment of Opioid Addiction
Abrupt opioid discontinuation can lead to development of opioid withdrawal symptoms (see ). Presentation of these symptoms has been associated with an increased risk of susceptible patients to relapse to illicit drug use and should be considered when assessing the risks and benefit of methadone use.
Tolerance and Physical Dependence
Tolerance is the need for increasing doses of opioids to maintain a defined effect such as analgesia (in the absence of disease progression or other external factors). Physical dependence is manifested by withdrawal symptoms after abrupt discontinuation of a drug or upon administration of an antagonist. Physical dependence and/or tolerance are not unusual during chronic opioid therapy.
If methadone is abruptly discontinued in a physically dependent patient, an abstinence syndrome may occur. The opioid abstinence or withdrawal syndrome is characterized by some or all of the following: restlessness, lacrimation, rhinorrhea, yawning, perspiration, chills, myalgia, and mydriasis. Other symptoms also may develop, including: irritability, anxiety, backache, joint pain, weakness, abdominal cramps, insomnia, nausea, anorexia, vomiting, diarrhea, or increased blood pressure, respiratory rate, or heart rate.
In general, chronically administered methadone should not be abruptly discontinued.
Special-Risk Patients
Methadone should be given with caution and the initial dose reduced in certain patients, such as the elderly and debilitated and those with severe impairment of hepatic or renal function, hypothyroidism, Addison's disease, prostatic hypertrophy, or urethral stricture. The usual precautions appropriate to the use of parenteral opioids should be observed and the possibility of respiratory depression should always be kept in mind.
Information for Patients
Methadone, like all opioids, may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving or operating machinery. The patient should be cautioned accordingly.
Methadone, like other opioids, may produce orthostatic hypotension in ambulatory patients.
Alcohol and other CNS depressants may produce an additive CNS depression, when taken with methadone, and should be avoided.
If a patient taking methadone experiences symptoms suggestive of an arrhythmia (such as palpitations, dizziness, lightheadedness, or syncope), that patient should seek immediate medical attention.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Data from published reports of carcinogenicity studies indicate that there was a significant increase in pituitary adenomas in female B6C2F1 mice consuming 15 mg/kg/day methadone for two years. This dose was approximately 0.6 times a human daily oral dose of 120 mg/day, on a body surface area basis. However, this finding was not seen in mice consuming 60 mg/kg/day (approximately 2.5 times a human daily oral dose of 120 mg/day). Furthermore, in a two-year study of dietary administration of methadone to Fischer 344 rats, there was no clear evidence for treatment related increase in the incidence of neoplasms, at doses as high as 28 mg/kg/day in males and 88 mg/kg/day in females (approximately 2.3 times and 7.1 times, respectively, a human daily oral dose of 120 mg/day) based on body surface area comparison.
In published reports, methadone tested negative in tests for chromosome breakage and disjunction and sex-linked recessive lethal gene mutations in germ cells of using feeding and injection procedures. Methadone treatment of male mice increased sex chromosome and autosome univalent chromosomes and translocations in multivalent chromosomes. Methadone tested positive in the DNA repair system and and mouse lymphoma forward mutation assays.
Pregnancy
Teratogenic effects:
Methadone has been detected in amniotic fluid and cord plasma at concentrations proportional to maternal plasma and in newborn urine at lower concentrations than corresponding maternal urine.
A retrospective series of 101 pregnant opiate-dependent women who underwent inpatient opiate detoxification with methadone did not demonstrate any increased risk of miscarriage in the 2 trimester or premature delivery in the 3 trimester.
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. The growth deficit does not appear to persist into later childhood. However, children born to women treated with methadone during pregnancy have been shown to demonstrate mild but persistent deficits in performance on psychometric and behavioral tests.
Methadone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Additional information on the potential risks of methadone may be derived from animal data. Methadone does not appear to be teratogenic in the rat or rabbit models. However, following large doses, methadone produced teratogenic effects in the guinea pig, hamster and mouse. One published study found that in hamster fetuses, subcutaneous methadone doses of 31 mg/kg or greater (estimated exposure was approximately 2 times a human daily oral dose of 120 mg/day on a mg/m basis, or equivalent to a human daily intravenous dose of 120 mg/day) on day 8 of gestation produced exencephaly and neurological effects. Some of the reported effects were observed at doses that were maternally toxic. In another study, a single subcutaneous dose of 22-24 mg/kg methadone (estimated exposure was approximately equivalent to a human daily oral dose of 120 mg/day on a mg/m basis; or half a human daily intravenous dose of 120 mg/day) 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/m basis; or 1.5 and 3 times a human daily intravenous dose of 120 mg/day) during days 6-15 and 6-18, respectively.
Nonteratogenetic Effects:
There are conflicting reports on whether the risk of sudden infant death syndrome (SIDS) is increased in infants born to women treated with methadone during pregnancy.
Abnormal fetal nonstress tests (NSTs) have been reported to occur more frequently when the test is performed 1-2 hours after a maintenance dose of methadone in late pregnancy compared to controls. Published animal studies suggest that perinatal exposure to opioids including methadone may alter neuronal development and behavior in the offspring. Perinatal methadone exposure in rats has been linked to alterations in learning ability, motor activity, thermal regulation, nociception responses and sensitivity to other drugs. Additional animal data demonstrates evidence for neurochemical changes in the brains of methadone-treated offspring, including the cholinergic, dopaminergic, noradrenergic and serotonergic systems.
Clinical Pharmacology for Pregnancy:
CLINICAL PHARMACOLOGY
Array
Labor and Delivery:
Nursing mothers:
Because of the potential for serious adverse reactions in nursing infants from methadone, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatric Use
Safety and effectiveness in pediatric patients below the age of 18 years have not been established.
Geriatric Use
Clinical studies of Methadone Hydrochloride Injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for elderly patients should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function and of concomitant disease or other drug therapy.
Renal Impairment
The use of methadone has not been extensively evaluated in patients with renal insufficiency.
Hepatic Impairment
The use of methadone has not been extensively evaluated in patients with hepatic insufficiency. Methadone is metabolized in the liver and patients with liver impairment may be at risk of accumulating methadone after multiple dosing.
Gender
The use of methadone has not been evaluated for gender specificity.
What are the side effects of Methadone?
Initial Administration:
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 include lightheadedness, dizziness, sedation, nausea, vomiting, and sweating. These effects seem to be more prominent in ambulatory patients and in those who are not suffering severe pain. In such individuals, lower doses of methadone are advisable.
Other adverse reactions that have been reported in patients (including opioid addicts taking methadone for detoxification or maintenance) receiving methadone include the following:
Body as a Whole:
Cardiovascular:
Digestive:
Hematologic and Lymphatic:
Metabolic and Nutritional:
Nervous:
Respiratory:
Skin and appendages:
Intramuscular and Subcutaneous: Local tissue reactions (pain, erythema, swelling), particularly with continuous subcutaneous infusion
Intravenous: Pruritis, urticaria, other skin rashes, and rarely, hemorrhagic urticaria
Special senses:
Urogenital:
Maintenance on a Stabilized Dose:
What should I look out for while using Methadone?
Methadone Hydrochloride Injection is contraindicated in patients with a known hypersensitivity to methadone hydrochloride or any other ingredient in Methadone Hydrochloride Injection. Methadone Hydrochloride Injection is contraindicated in any situation where opioids are contraindicated such as: patients with respiratory depression (in the absence of resuscitative equipment or in unmonitored settings), and in patients with acute bronchial asthma or hypercarbia.
What might happen if I take too much Methadone?
How should I store and handle Methadone?
Store the kit at 2°-8°C (36°-46°F) and protect from light.ArrayStore the kit at 2°-8°C (36°-46°F) and protect from light.ArrayMultiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006Multiple-Dose Vials: 10 mg/mL, 20 mL, NDC 66479-530-02One vial per packageProtect from light. Store in carton until contents have been used.Store at 25°C (77°F); excursions are permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature]Manufactured by: AAIPharma Inc., Charleston, SC 29405Marketed by: Xanodyne Pharmaceuticals Inc., Newport, KY 41071XanodynePharmaceuticals, inc.©2006, Xanodyne Pharmaceuticals Inc. PC3374B Rev. 03-2006
Clinical Information
Chemical Structure
No Image foundClinical Pharmacology
Methadone hydrochloride is a μ agonist; a synthetic opioid analgesic with multiple actions qualitatively similar to those of morphine, the most prominent of which involve the central nervous system and organs composed of smooth muscle. The principal therapeutic uses for methadone are for analgesia and for detoxification or maintenance in opioid addiction. The methadone abstinence syndrome, although qualitatively similar to that of morphine, differs in that the onset is slower, the course is more prolonged, and the symptoms are less severe. Some data also indicate that methadone acts as an antagonist at the N-methyl-D-aspartate (NMDA) receptor. The contribution of NMDA receptor antagonism to methadone's efficacy is unknown. Other NMDA receptor antagonists have been shown to produce neurotoxic effects in animals.
Non-Clinical Toxicology
Methadone Hydrochloride Injection is contraindicated in patients with a known hypersensitivity to methadone hydrochloride or any other ingredient in Methadone Hydrochloride Injection. Methadone Hydrochloride Injection is contraindicated in any situation where opioids are contraindicated such as: patients with respiratory depression (in the absence of resuscitative equipment or in unmonitored settings), and in patients with acute bronchial asthma or hypercarbia.In vitro
Methadone given on a fixed-dose schedule may have a narrow therapeutic index in certain patient populations, especially when combined with other drugs, and should be reserved for cases where the benefits of opioid analgesia outweigh the known potential risks of cardiac conduction abnormalities, respiratory depression, altered mental states and postural hypotension. Methadone Hydrochloride Injection should be used with caution in elderly and debilitated patients; patients who are known to be sensitive to central nervous system depressants, such as those with cardiovascular, pulmonary, renal, or hepatic disease; and in patients with comorbid conditions or concomitant medications which may predispose to dysrhythmia.
Selection of patients for treatment with methadone should be governed by the same principles that apply to the use of other parenteral opioids (see ). Physicians should individualize treatment in every case (see ), taking into account the high degree of interpatient variability in response to and metabolism of methadone.
Reference
This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
"https://dailymed.nlm.nih.gov/dailymed/"
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Clonazepam Description Each single-scored tablet, for oral administration, contains 0.5 mg, 1 mg, or 2 mg Clonazepam, USP, a benzodiazepine. Each tablet also contains corn starch, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and povidone. Clonazepam tablets USP 0.5 mg contain Yellow D&C No. 10 Aluminum Lake. Clonazepam tablets USP 1 mg contain Yellow D&C No. 10 Aluminum Lake, as well as FD&C Blue No. 1 Aluminum Lake. Chemically, Clonazepam, USP is 5-(o-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one. It is a light yellow crystalline powder. It has the following structural formula: C15H10ClN3O3 M.W. 315.72Tips
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