Classified as opiate analgesics, both methadone and oxycodone are medications used to treat moderate to severe pain. Combining these medications can carry risks of increased side effects that may be lethal in some cases, such as with respiratory depression. In some cases, however, the two medications may be combined safely under a doctor's supervision to treat specific cases of pain. Due to the potential safety hazards, though, they should not be mixed unless a doctor specifically advises it.
Methadone and oxycodone are both used to treat similar levels of pain, but the length of pain relief offered by each varies. The effects of methadone can last for 24 to 36 hours, making it appropriate for treating chronic pain. Oxycodone, in its instant-release formulation, generally lasts for around six to eight hours, and around 12 hours in an extended release formulation. Depending on its formulation, it may be used to treat acute pain that appears suddenly, or chronic pain.
Doctors may use a combination of opioid analgesics to treat certain medical conditions. Conditions that involve a basic level of chronic pain that must be controlled, along with acute pain that may arise unexpectedly, often involve a combination of a long-acting and short-acting opiate. In such a case, doctors may prescribe methadone with oxycodone, with methadone taken on a daily basis for chronic pain, and oxycodone taken as needed when acute pain occurs.
The side effects of these medications often increase when they are combined. For this reason, methadone and oxycodone should only be mixed under the supervision of a medical professional. Common side effects that result from taking either or both medications can include nausea, stomach discomfort, and drowsiness. Large doses of opioids can result in more severe side effects, particularly respiratory depression, or difficulty breathing. In severe cases, respiratory depression can be fatal, and mixing opioids increases the chance of this effect developing.
Drug interactions also become more likely when mixing methadone and oxycodone. Taking both medications at once increases the risk of potentially dangerous sedation when combined with other central nervous system (CNS) depressants such as alcohol, benzodiazepines, and sleeping pills. Certain blood pressure medications may have increased reactions with a combination of these drugs, as well. Both opioid painkillers can be addictive, and the potential for addiction can be much greater when they are taken together, which is another reason that a doctor should monitor any combination of the two.