Methasan (Methadone Hydrochloride)

• Methadone acts on opioid receptors to address conditions related to opioid dependence and severe pain.
• Opioid dependence: stabilizes patients by reducing withdrawal symptoms and cravings during maintenance therapy.
• Chronic pain: provides long‑acting analgesia for severe, persistent pain unresponsive to other opioids.
• Palliative care: offers sustained pain relief in end‑of‑life settings.

• Methadone is a full agonist at the μ‑opioid receptor, binding with high affinity and activating the receptor to inhibit nociceptive neurotransmission. By increasing potassium‑channel opening and reducing calcium influx, it hyperpolarizes neurons, decreasing the release of excitatory neurotransmitters. Its long half‑life maintains sustained receptor occupancy, supporting both analgesia and opioid‑dependence maintenance.

Methadone may cause a range of adverse reactions, which are grouped by frequency.

Common Side Effects

• Nausea: feeling of sickness or urge to vomit.
• Constipation: reduced bowel movements.
• Drowsiness: increased sleepiness or fatigue.
• Sweating: excessive perspiration.

Serious or Rare Side Effects

• Respiratory depression: slowed or shallow breathing that can be life‑threatening.
• QT interval prolongation: heart rhythm disturbance that may lead to arrhythmia.
• Severe hypotension: marked drop in blood pressure.
• Allergic reactions: rash, itching, swelling, or anaphylaxis.

When prescribing Methasan, clinicians should observe several safety measures to minimize risk.

• Assess respiratory function: monitor breathing, especially during initiation and dose changes.
• Evaluate cardiac status: obtain baseline ECG to detect QT prolongation risk.
• Use caution in hepatic impairment: adjust dosing and monitor liver function.
• Avoid use in acute intoxication: contraindicated in patients with concurrent CNS depressant overdose.
• Store at ambient temperature: keep in the original pack, protect from moisture and light.

Methadone can interact with other medicines, altering its effects or increasing toxicity.

Major Interactions (Avoid)

• Central nervous system depressants: concurrent use with benzodiazepines, alcohol, or barbiturates may cause profound sedation and respiratory depression.
• Monoamine oxidase inhibitors: co‑administration can precipitate serotonin syndrome or hypertensive crisis.
• QT‑prolonging drugs: agents such as certain antiarrhythmics or antipsychotics increase the risk of cardiac arrhythmias.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors: drugs like ketoconazole can raise methadone plasma levels, requiring dose adjustment.
• CYP3A4 inducers: agents such as rifampin may lower methadone concentrations, potentially reducing efficacy.