MedicinecontrolledEssential

Methadone

An opioid (Physeptone) used to treat heroin dependence, and for severe pain.

Clinical information

Common uses

heroin and other opioid dependence (maintenance or detox)
severe pain and end of life care

Common side effects

constipation
feeling or being sick
feeling cold and sweaty
sleepiness, tiredness or dizziness
dry mouth, eyes and nose

Cautions

overdose can slow or stop breathing — life-threatening
addictive — dose must be reduced gradually
avoid alcohol — serious side effect risk
avoid grapefruit — worsens side effects

Interactions

other opioids (morphine, codeine, buprenorphine) — do not combine
sleeping tablets and benzodiazepines (diazepam, temazepam, zopiclone)
MAOI antidepressants (phenelzine, tranylcypromine)
heart rhythm medicines (amiodarone, verapamil, diltiazem)
epilepsy medicines (phenytoin, carbamazepine)
St John's wort — may stop it working properly

Pregnancy: may be taken if needed — baby monitored for withdrawal

Reference information, not medical advice — always follow your doctor or pharmacist. Source: NHS Medicines A–Z, nhs.uk/medicines/methadone (accessed 2026-08-16)

Approved brands & formulations4

Brand name	Dosage form	Strength	Importer	Category
Methadone	Oral Liquid	5mg/ml	MFDA designated importers with Pre Authorization approval before import	controlled
Methadone	Oral Liquid	5mg/ml	authorized medicine importers	controlled
Methadone	Oral Liquid	10mg/ml	MFDA designated importers with Pre Authorization approval before import	controlled
R-METH	Oral Liquid	5mg/ml / 1000ml	—	controlled