Methadone Side Effects: Brand names are Methadose and Dolophine. Dosage forms available are 5 and 10 mg tablets and various concentration solutions. Also available in a 40 mg tablet restricted for use in authorized opioid detox facilities. Methadone has become very well known for its use in so called, “methadone clinics” where opioid addicts, primarily heroin addicts receive daily methadone doses to prevent opioid withdrawal and to facilitate abstinence from heroin use. Methadone is also used as an opioid analgesic. Its primary benefits are relatively low cost and fairly long half-life. Methadone side effects are largely class side effects and mimic oxycodone side effects and those of other opioid medications.

Black Box Warnings: Methadone has incomplete cross tolerance, and the fact that an individual has high tolerance to another opioid does not assure tolerance to methadone, and iatrogenic overdose has occurred by initiation of high dose methadone treatment on the assumption of this opioid tolerance. Respiratory depression and death can occur with methadone used, and is especially a concern during dose titration and conversion from other opioids. It is key to understand that the respiratory depression methadone side effects occur later and last longer that the desired analgesic benefits of methadone. QT prolongation and torsade de pointes has occurred with methadone, and its use should be considered only when the potential benefits outweigh these risks. Methadone use for opioid withdrawal therapy is only permitted by authorized methadone clinics with specific state authority.

Common Methadone side effects: The common methadone side effects are similar to the common side effects of most opioid drugs. These include constipation, nausea and vomiting, sweating, lightheadedness, dizziness and confusion. Sedation is very common with methadone use, especially in non-opioid tolerant patients.

Serious Methadone Side Effects: First see the Black Box warnings above. Respiratory arrest, cardiac arrest, death, prolongued QT prolongation, torsades de pointes, ventricular tachycardia, ventricular fibrillation, severe bradycardia, cardiomyopathy and death are all possible with methadone, and are serious cardiorespiratory methadone side effects. Hypotension, seizures, syncope, pulmonary edema and respiratory depression are also seen. The most common of the serious methadone side effects is probably abuse and diversion of the medication. Prescription opioid abuse is epidemic in the U. S. and abroad and is a leading cause of drug overdose deaths.

Cautions and Drug Interactions: The list of cautions for methadone use is very long, and readers should refer to the manufacturer’s prescriber guidelines for a complete list. The more common conditions include significant cardiac or respiratory disease, especially cardiac conduction abnormalities. Use in patients at risk for urinary retention is cautioned. Use with thioridazine is contraindicated, and use with other phenothiazines may increase risk of severe constipation and even gastrointestinal obstruction. Use with quinidine can greatly increase cardiac arrhythmia risks. Use with venlafaxine or other tricyclic or tetracyclic antidepressants may combine to cause serious QT prolongation. Use with any medications that can affect cardiac conduction is cautioned. Use with other opioids may lead to additive effects and increase the risk of methadone side effects.

Pregnancy and Lactation: Pregnancy Category C and use in lactation is probably safe. Use of opioids in late pregnancy can lead to opioid habituation in the fetus, and to serious opioid withdrawal after delivery for the neonate.

Unusual Methadone Side Effects: The cardiac rhythm side effects of methadone are relatively unique to this particular opioid, and warrant particular note.

Special Considerations: Abuse and diversion of opioids including methadone are serious problems. Special care needs to be taken to attempt to avoid these concerns. Most physicians insist on a pain medication agreement when opioids are prescribed for long term pain management. In addition drug screening is commonly done randomly in physician offices to assure the patient is using the drug themselves and not to look for concurrent other opioid or illegal drug use. Even with diligent attempts to prevent abuse and diversion these issues remain rampant in many U.S. communities.

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