Methadone Hydrochloride

What it is and how it works

Mechanism of Action Methadone hydrochloride is a mu-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.

Indications

INDICATIONS AND USAGE 1. Methadone Hydrochloride Injection is indicated for the management of severe and persistent pain that requires an opioid analgesic and that cannot be adequately treated with alternative options, including immediate-release opioids. Limitations of Use • Because of the risks of addiction, abuse, misuse, overdose, and death, which can occur at any dosage or duration (see WARNINGS ), and persist over the course of therapy, reserve opioid analgesics, including Methadone Hydrochloride Injection, for use in patients for whom alternative treatment options are ineffective, not tolerated, or would be otherwise inadequate to provide sufficient management of pain. • Methadone Hydrochloride Injection is not indicated as an as-needed (prn) analgesic. 2. For use in temporary treatment of opioid dependence in patients unable to take oral medication. Limitations of Use • Injectable methadone products are not approved for the outpatient treatment of opioid dependence.

Dosage and administration (summary)

DOSAGE AND ADMINISTRATION Important General Information Consider the following important factors that differentiate methadone from other opioids: • The peak respiratory depressant effect of methadone occurs later and persists longer than its peak pharmacologic effect. • A high degree of opioid tolerance does not eliminate the possibility of methadone overdose, iatrogenic or otherwise. Deaths have been reported during conversion to methadone from chronic, high-dose treatment with other opioid agonists and during initiation of methadone treatment of addiction in subjects previously abusing high doses of other opioid agonists.

Contraindications

CONTRAINDICATIONS Methadone Hydrochloride Injection is contraindicated in patients with: • Significant respiratory depression • Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment • Known or suspected gastrointestinal obstruction, including paralytic ileus • Hypersensitivity to methadone hydrochloride (e.g. anaphylaxis) or any other ingredient in Methadone Hydrochloride Injection.

Warnings and precautions

WARNINGS Addiction, Abuse and Misuse Methadone Hydrochloride Injection contains methadone, a Schedule II controlled substance. As an opioid, Methadone Hydrochloride Injection exposes users to the risks of addiction, abuse, and misuse. Although the risk of addiction in any individual is unknown, it can occur in patients appropriately prescribed Methadone Hydrochloride Injection. Addiction can occur at recommended doses and if the drug is misused or abused.

Pregnancy

Pregnancy There are no pharmacokinetic studies of parenteral methadone in pregnancy. The disposition of oral methadone has been studied in approximately 30 pregnant patients in 2 nd and 3 rd trimesters. Elimination of methadone was significantly changed in pregnancy.

Storage and supply

HOW SUPPLIED Methadone Hydrochloride Injection USP, 200 mg/20 mL (10 mg/mL) is a clear, colorless solution and is available in: NDC 67457-217-20 20 mL Multiple-Dose Vials: One vial per carton Store at 20°C to 25°C (68°F to 77°F), with excursions permitted between 15°C to 30°C (59°F to 86°F). Protect from light.

Source: Methadone Hydrochloride (Methadone Hydrochloride) — US FDA prescribing information, 2025-12-31, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.