Methadone Ι.Φ.Ε.Τ. (Methadone Hydrochloride)

• Methadone acts on the opioid system and is used in specific clinical pathways related to dependence and pain.
• Opioid dependence treatment: Supports maintenance therapy and reduces withdrawal symptoms in individuals with opioid use disorder.
• Chronic pain management: Provides long‑acting analgesia for severe, persistent pain when other opioids are insufficient.
• Detoxification from opioids: Facilitates safe transition during medically supervised withdrawal by delivering a controlled opioid effect.

• Methadone exerts its primary effect as a full agonist at the µ‑opioid receptor, producing analgesia and suppressing opioid cravings. It also antagonizes NMDA receptors and inhibits the reuptake of serotonin and norepinephrine, contributing to its analgesic and anti‑withdrawal properties while influencing pain modulation pathways.

Methadone may cause a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Nausea and vomiting: Gastrointestinal upset is frequently reported.
• Constipation: Reduced bowel motility is common with opioid therapy.
• Dizziness or light‑headedness: May occur, especially when standing.
• Sweating: Excessive perspiration can be experienced.
• Sedation or drowsiness: Can affect alertness.
• Dry mouth: Reduced salivation is typical.

Serious or Rare Side Effects

• Respiratory depression: Life‑threatening slowing of breathing.
• QT interval prolongation: May lead to cardiac arrhythmias.
• Severe hypotension: Marked drop in blood pressure.
• Adrenal insufficiency: Rare endocrine disturbance.
• Seizures: Uncommon but serious neurologic event.
• Cardiac arrhythmia: Irregular heart rhythm beyond QT issues.

• When prescribing methadone, clinicians should observe several safety measures to minimize risks.
• Assess cardiac risk: Evaluate baseline QT interval and correct electrolyte abnormalities before initiation.
• Monitor respiratory function: Especially in opioid‑naïve patients or those with pulmonary disease.
• Avoid abrupt discontinuation: Taper dose gradually to prevent withdrawal syndrome.
• Use caution in hepatic impairment: Adjust dosing as methadone is metabolized by the liver.
• Pregnancy and breastfeeding: Discuss potential risks and benefits with the patient.
• Store at ambient temperature: Keep in the original container, protect from moisture and light.

Methadone interacts with various medicines; awareness of the interaction level guides clinical decisions.

Major Interactions (Avoid)

• Central nervous system depressants (e.g., benzodiazepines, barbiturates): Increased risk of respiratory depression.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): May raise methadone plasma concentrations.
• QT‑prolonging agents (e.g., sotalol, quinidine): Additive risk of cardiac arrhythmias.

Moderate Interactions (Monitor Closely)

• CYP2B6 inducers (e.g., rifampin, carbamazepine): May reduce methadone levels, risking withdrawal.
• Selective serotonin reuptake inhibitors: Potential for serotonin syndrome.
• Alcohol: Enhances sedative effects and respiratory depression.