Methadone Hydrochloride Ascot Laboratories (Ireland) (Methadone Hydrochloride)

Methadone Hydrochloride, a synthetic opioid, acts on the μ‑opioid receptor pathway to provide analgesia and reduce opioid withdrawal.

• Chronic pain: provides long‑acting analgesia for patients with moderate to severe persistent pain.
• Opioid dependence: serves as maintenance therapy to suppress withdrawal symptoms and cravings in individuals with opioid use disorder.
• Palliative care: offers pain control for patients with terminal illness.

• Methadone Hydrochloride is a full agonist at the μ‑opioid receptor, producing analgesia and attenuating withdrawal by activating opioid pathways. It also antagonizes NMDA receptors and inhibits the reuptake of serotonin and norepinephrine, contributing to its analgesic and anti‑withdrawal effects.

Methadone Hydrochloride may cause a range of adverse reactions.

Common Side Effects

• Nausea
• Constipation
• Sweating
• Drowsiness
• Dry mouth
• Dizziness

Serious or Rare Side Effects

• Respiratory depression
• QT interval prolongation
• Seizures
• Severe hypotension
• Adrenal insufficiency
• Allergic reactions including anaphylaxis

When prescribing Methadone Hydrochloride, clinicians should consider several safety measures.

• Assess opioid tolerance: confirm patient’s prior exposure to opioids before initiating therapy.
• Monitor respiratory function: especially during dose titration and in patients with pulmonary disease.
• Evaluate cardiac status: baseline ECG is recommended due to risk of QT prolongation.
• Use caution in hepatic impairment: dose adjustments may be required.
• Avoid abrupt discontinuation: taper gradually to prevent withdrawal.
• Store at ambient temperature: keep in the original container, protect from moisture.

Methadone Hydrochloride interacts with several drug classes that may alter its safety or efficacy.

Major Interactions (Avoid)

• CNS depressants (e.g., benzodiazepines, alcohol): increased risk of respiratory depression.
• MAO inhibitors: potential for severe serotonin syndrome.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): may raise methadone plasma levels.
• QT‑prolonging agents (e.g., haloperidol, quinidine): additive cardiac risk.
• Potent CYP2B6 inducers (e.g., rifampin): may reduce methadone effectiveness.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., carbamazepine): may lower methadone concentrations.
• Other opioids: cumulative opioid effect.
• SSRIs and SNRIs: possible serotonin syndrome.
• Antihistamines: enhanced sedation.
• Diuretics: may affect electrolyte balance influencing QT interval.