Methadone respiratory

Methadone is not without side effects. Although it is less addictive than other opiates, methadone can be abused and requires monitored use. Common side effects include sedation and constipation. Methadone is also safer than other opiates in overdose but does require careful monitoring of respiratory status when an overdose occurs. 

Respiratory depression Accidental overdose with long-acting opioids (eg, methadone, levomethadyl) may result in prolonged respiratory depression. While nalmefene has a longer duration of action than naloxone in fully reversing doses, be aware that a recurrence of respiratory depression is possible. Observe patients until there is no reasonable risk of recurrent respiratory depression. 

For the complete or partial reversal of narcotic depression, including respiratory depression, induced by opioids including natural and synthetic narcotics, propoxyphene, methadone, nalbuphine, butorphanol, and pentazocine. Also indicated for the diagnosis of suspected acute opioid overdosage. 

The concurrent administration of methadone to heroin addicts known to be recidivists has been questioned because of the increased risk of overdose death secondary to respiratory arrest. Buprenorphine, a partial M-receptor agonist with long-acting properties, has been found to be effective in opioid detoxification and maintenance programs and is presumably associated with a lower risk of such overdose fatalities. 

Methadone Slow-acting agonist of M-opioid receptor Acute effects similar to morphine (see text) Substitution therapy for opioid addicts High oral bioavailability half-life highly variable among individuals (range 4-130 h) Toxicity Respiratory depression, constipation, miosis, tolerance, dependence, and withdrawal symptoms... 

Methadone is a synthetic opioid, clinically available in the U.S. since 1947.8 It exists in the dextro- and levo-rotatory forms with the levo-isoform possessing approximately 8 to 50 times more pharmacological activity.27 34 Methadone acts on the CNS and cardiovascular system producing respiratory and circulatory depression. Methadone also produces miosis and increases the tone of smooth muscle in the lower gastrointestinal tract while decreasing the amplitude of contractions. It is used clinically for the treatment of severe pain and in maintenance programs for morphine and heroin addicts.34... 

Naloxone (Narcan) and naltrexone hydrochloride (Trexan) reverse the respiratory depressant action of narcotics related to morphine, meperidine, and methadone. They differ from other narcotic analgesics in several respects. Naloxone does not cause respiratory depression, pupillary constriction, sedation, or analgesia. However, it does antagonize the actions of pentazocine. Naloxone neither antagonizes the respiratory depressant effects of barbiturates and other hypnotics nor aggravates their depressant effects on respiration. Similar to nalorphine, naloxone precipitates an abstinence syndrome when administered to patients addicted to opiate-like drugs. 

Another important side effect of all opiates on the central nervous system is respiratory depression. This is caused by an inhibitory effect on the brain stem, which is the part of the brain that controls breathing and other involuntary bodily systems such as heart beat, etc. Like nausea and vomiting, people who take methadone and other opiates normally develop a tolerance to this side effect. However, even people who have taken methadone for a long period of time can develop major respiratory depression. 

Actions The analgesic activity of methadone is equivalent to that of morphine. Methadone exhibits strong analgesic action when administered orally, in contrast to morphine, which is only partially absorbed from the gastrointestinal tract. The miotic and respiratory depressant actions of methadone have average half-lives of 24 hours. Like morphine, methadone increases biliary pressure, and is also constipating. 

Heroin and methadone produced a rapid and dramatic reduction in both respiratory rate and cortical hemoglobin oxygenation, while saline had no effects. The authors suggested that opioid-induced acute deoxygenation of cortical hemoglobin was probably associated with respiratory depression. In one in three subjects, oxygen saturation after intravenous heroin fell rapidly, a finding that has not previously been described in humans. 

BARBITURATES ANALGESICS - OPIOIDS 1. Barbiturates t sedative effects of opioids 2.1 efficacy of fentanyl and methadone with phenobarbital and primidone 1. Additive sedative effect. 2. t hepatic metabolism of fentanyl and methadone 1. Monitor respiratory rate and conscious levels 2. Be aware that the dose of fentanyl and methadone may need to t... 

IMATINIB ANALGESICS-OPIOIDS May cause t plasma concentrations, with a risk of toxic effects of codeine, dextromethorphan, hydroxycodone, methadone, morphine, oxycodone, pethidine and tramadol Inhibition of CYP2D6-mediated metabolism of these opioids Monitor for clinical efficacy and toxicity. Warn patients to report t drowsiness, malaise or anorexia. Measure amylase and lipase levels if toxicity is suspected. Tramadol causes less respiratory depression than other opiates, but need to monitor BP and blood counts, and advise patients to report wheezing, loss of appetite and fainting attacks. Need to consider 1 dose. Methadone may cause Q-T prolongation the CHM has recommended that patients with heart and liver disease who are on methadone should be carefully monitored for heart conduction abnormalities such as Q-T prolongation on ECG as they may lead to sudden death. Also need to monitor patients on more than 100 mg methadone daily and thus an t in plasma concentrations necessitates close monitoring of cardiac and respiratory function... 

OPIOIDS ANTICANCER AND IMMUNOMODULATING DRUGS - CYTOTOXICS 1. Imatinib may cause t plasma concentrations, with a risk of toxic effects of codeine, dextromethorphan, hydroxycodone, methadone, morphine, oxycodone, pethidine and tramadol 2. Unpredictable reactions may occur associated with hypotension and respiratory depression when procarbazine is co-administered with alfentanil, fentanyl, sufentanil or morphine... 

SAFETY PROFILE Poison by ingestion, intraperitoneal, intravenous, subcutaneous, and intraduodenal routes. Human systemic effects coma, nausea or vomiting, respiratory changes, respiratory depression, somnolence. An experimental teratogen. Experimental reproductive effects. Caution Abuse leads to habituation or addiction. When heated to decomposition it emits toxic fumes of NOx. See also METHADONE HYDROCHLORIDE. 

Ciprofloxacin, given to a patient who had been successfully treated with methadone for more than 6 years, caused profound sedation, confusion, and respiratory depression (73). This may have been due to inhibition of CYP1A2 and CYP3A4, two of the isozymes involved in the metabolism of methadone. 

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