Mephenon (Methadone Hydrochloride)

Methadone Hydrochloride is an opioid agonist used in pain management and opioid dependence treatment.

• Severe chronic pain: provides long‑acting analgesia for patients with persistent severe pain.
• Opioid dependence: suppresses withdrawal symptoms and supports maintenance therapy.
• Opioid detoxification: facilitates gradual tapering of opioid use during supervised withdrawal programs.

• Methadone Hydrochloride acts as a high‑affinity agonist at the mu‑opioid receptor, producing analgesia and reducing opioid craving. Its additional antagonism of NMDA receptors contributes to modulation of pain pathways and may lessen opioid tolerance. The combined actions result in effective pain control and mitigation of withdrawal symptoms during opioid dependence treatment.

Methadone Hydrochloride may cause a range of adverse reactions, from mild to serious.

Common Side Effects

• Nausea: feeling of sickness or urge to vomit.
• Constipation: reduced bowel movements and hard stools.
• Drowsiness: increased sleepiness or fatigue.
• Sweating: excessive perspiration unrelated to temperature.
• Dizziness: sensation of light‑headedness or unsteadiness.
• Dry mouth: reduced salivation leading to a parched feeling.

Serious or Rare Side Effects

• Respiratory depression: slowed or shallow breathing that can be life‑threatening.
• QT interval prolongation: cardiac electrical disturbance that may cause arrhythmia.
• Severe hypotension: marked drop in blood pressure leading to fainting.
• Cardiac arrhythmia: irregular heart rhythm requiring immediate medical attention.
• Adrenal insufficiency: inadequate production of adrenal hormones.
• Seizures: uncontrolled electrical activity in the brain.

When using Methadone Hydrochloride, clinicians should observe several safety measures.

• Respiratory assessment: monitor breathing rate and oxygen saturation, especially during initiation.
• Cardiac monitoring: obtain baseline ECG and watch for QT prolongation.
• Hepatic function: adjust dosing in patients with liver impairment.
• Concomitant CNS depressants: avoid or use with caution to reduce risk of respiratory depression.
• Gradual tapering: discontinue only under medical supervision to prevent withdrawal.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Methadone Hydrochloride interacts with several drug classes; careful management is required.

Major Interactions (Avoid)

• Central nervous system depressants (e.g., benzodiazepines, alcohol): may cause profound respiratory depression.
• Monoamine oxidase inhibitors: can precipitate severe hypotension or serotonin syndrome.
• QT‑prolonging agents (e.g., certain antiarrhythmics, antipsychotics): increase risk of cardiac arrhythmias.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): may raise methadone plasma levels.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce methadone effectiveness.
• Selective serotonin reuptake inhibitors: require monitoring for additive serotonergic effects.