Methadone hydrochlorideProduct ingredient for Methadone

Name
Methadone hydrochloride
Drug Entry
Methadone

Methadone is a potent synthetic analgesic that works as a full µ-opioid receptor (MOR) agonist and N-methyl-d-aspartate (NMDA) receptor antagonist. As a full MOR agonist, methadone mimics the natural effects of the body's opioids, endorphins, and enkephalins through the release of neurotransmitters involved in pain transmission. It also has a number of unique characteristics that have led to its increased use in the last two decades; in particular, methadone has a lower risk of neuropsychiatric toxicity compared to other opioids (due to a lack of active metabolites), minimal accumulation in renal failure, good bioavailability, low cost, and a long duration of action.21,22,23,14,19,20

Due to its unique mechanism of action, methadone is particularly useful for the management of hard to treat pain syndromes such as neuropathic pain and cancer pain requiring higher and more frequent doses of shorter-acting opioids.15,16,18 Compared with morphine, the gold standard reference opioid, methadone also acts as an agonist of κ- and σ-opioid receptors, as an antagonist of the N-methyl-D-aspartate (NMDA) receptor, and as an inhibitor of serotonin and norepinephrine uptake.2,7 Specifically by inhibiting the NMDA receptor, methadone dampens a major excitatory pain pathway within the central nervous system.12 Compared to other opioids, methadone's effects on NMDA inhibition may explain it's improved analgesic efficacy and reduced opioid tolerance.16,17

Methadone shares similar effects and risks of other opioids such as morphine, hydromorphone, oxycodone, and fentanyl. However, it also has a unique pharmacokinetic profile. Compared with short-acting and even extended-release formulations of morphine, methadone displays a comparatively longer duration of action and half-life. These effects make methadone a good option for the treatment of severe pain and addiction as fewer doses are needed to maintain analgesia and prevent opioid withdrawal symptoms. However, methadone also has an unpredictable half-life with interindividual variability, which leads to an unpredictable risk of respiratory depression and overdose when initiating or titrating therapy.8

Overall, methadone's pharmacological actions result in analgesia, suppression of opioid withdrawal symptoms, sedation, miosis, sweating, hypotension, bradycardia, nausea and vomiting (via binding within the chemoreceptor trigger zone), and constipation. At higher doses, methadone use can result in respiratory depression, overdose, and death.21,22,23

Treatment of opioid addiction with methadone, buprenorphine, or slow-release oral morphine (SROM) is termed Opioid Agonist Treatment (OAT) or Opioid Substitution Therapy (OST). The intention of substitution of illicit opioids with the long-acting opioids used in OAT is to prevent withdrawal symptoms for 24-36 hours following dosing to ultimately reduce cravings and drug-seeking behaviours. Use of OAT is also intended to lead to social stabilization by reducing crime rates, incarceration, use of illicit opioids such as heroin or fentanyl, and ultimately marginalization.13 Illegally purchased opioids present many other harms in addition to overdose as they can be injected and may be laced with other substances that increase the risk of harm or overdose. Provision of OAT is often combined with education about harm reduction including use of clean needles and injection supplies in an effort to reduce the risks associated with injection drug use such as contraction of HIV and Hepatitis C and other complications including skin infections, abscesses, or endocarditis.

Accession Number
DBSALT000346
Structure
Thumb
Synonyms
Methadone HCl
External IDs
AN-148
UNII
229809935B
CAS Number
1095-90-5
Weight
Average: 345.906
Monoisotopic: 345.18594223
Chemical Formula
C21H28ClNO
InChI Key
FJQXCDYVZAHXNS-UHFFFAOYSA-N
InChI
InChI=1S/C21H27NO.ClH/c1-5-20(23)21(16-17(2)22(3)4,18-12-8-6-9-13-18)19-14-10-7-11-15-19;/h6-15,17H,5,16H2,1-4H3;1H
IUPAC Name
6-(dimethylamino)-4,4-diphenylheptan-3-one hydrochloride
SMILES
Cl.CCC(=O)C(CC(C)N(C)C)(C1=CC=CC=C1)C1=CC=CC=C1
PubChem Compound
14184
ChemSpider
13556
ChEBI
50140
ChEMBL
CHEMBL1200825
Wikipedia
Methadone
Predicted Properties
PropertyValueSource
Water Solubility0.0059 mg/mLALOGPS
logP4.14ALOGPS
logP5.01ChemAxon
logS-4.7ALOGPS
pKa (Strongest Acidic)19.79ChemAxon
pKa (Strongest Basic)9.12ChemAxon
Physiological Charge1ChemAxon
Hydrogen Acceptor Count2ChemAxon
Hydrogen Donor Count0ChemAxon
Polar Surface Area20.31 Å2ChemAxon
Rotatable Bond Count7ChemAxon
Refractivity97.27 m3·mol-1ChemAxon
Polarizability36.3 Å3ChemAxon
Number of Rings2ChemAxon
Bioavailability1ChemAxon
Rule of FiveNoChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleNoChemAxon