methadone hydrochloride at a glance
Medicine class
Long-acting opioid agonist.
Main role
Suppresses opioid withdrawal and cravings as part of a wider treatment programme.
Administration
Most selected products are swallowed as liquids. The concentrate requires dilution; injection is given by a healthcare professional.
What is methadone hydrochloride used for?
Licensed uses vary between products and formulations.
Treatment of dependence on heroin or other opioids, including substitution, maintenance or withdrawal treatment within a broader supervised programme.
Selected oral and injectable products are licensed for moderate to severe pain; injection is described as an alternative to morphine.
How does methadone hydrochloride work?
Methadone predominantly activates mu-opioid receptors. This reduces opioid withdrawal and craving and produces analgesia, but can slow breathing and bowel movement. Its long, variable persistence can cause accumulation.
methadone hydrochloride preparations and strengths
Oral mixture
Route: Oral
Strengths: 1 mg/mL
Oral solution
Route: Oral
Strengths: 1 mg/1 mL, 1 mg/mL
Tablet
Route: Oral
Strengths: 5 mg
How to take methadone hydrochloride
Follow the individual prescription and treatment plan exactly. Oral solutions are swallowed; concentrated product is intended to be diluted by the pharmacist or prescriber. Injectable methadone is given under the skin or into a muscle by a healthcare professional. Do not stop suddenly, share it or alter the formulation yourself.
Avoid alcohol and grapefruit or grapefruit juice.
Store take-home methadone securely, out of sight and reach of children and others.
methadone hydrochloride side effects
Common or expected effects
- Constipation
- Feeling or being sick
- Sleepiness, tiredness or dizziness
- Headache
- Sweating or feeling cold
- Dry mouth, nose or eyes
Get urgent medical advice
- Slow, shallow or difficult breathing, or extreme drowsiness
- Irregular, unusually fast or unusually slow heartbeat
- Fainting or inability to wake
- Severe allergic swelling or difficulty swallowing
- Hallucinations, marked confusion or major mood changes
methadone hydrochloride in pregnancy
Methadone may be continued or started during pregnancy when benefits, particularly preventing heroin use and withdrawal, outweigh potential risks. Pregnancy requires a coordinated specialist plan, and the newborn may need observation and treatment for withdrawal. Do not stop suddenly; contact the prescriber, midwife or treatment service if pregnant or planning pregnancy.
methadone hydrochloride while breastfeeding
For opioid-dependence treatment, methadone is a preferred option during breastfeeding because experience is greater, although specialist assessment and infant monitoring are necessary. Small amounts enter breast milk. Seek urgent help if the baby is unusually sleepy, pale, limp or has breathing difficulty.
methadone hydrochloride interactions
Methadone has important interactions. Check all prescribed, non-prescribed and herbal products with a pharmacist or prescriber.
Alcohol
Adds to sedation, low blood pressure and breathing suppression; avoidance is advised.
Benzodiazepines, sleeping medicines and other sedatives
Can cause profound sedation, respiratory depression, coma or death.
Common questions about methadone hydrochloride
Answers are fully visible for fast scanning and source review.
Can methadone hydrochloride cause dependence?
Yes. Physical dependence and addiction can occur, including when prescribed. Treatment should be reviewed and stopped gradually under clinical supervision.
Can I drive while taking methadone hydrochloride?
Do not drive if it causes sleepiness, dizziness, blurred vision, poor coordination or impaired judgement. A medical defence under UK drug-driving rules applies only when it was prescribed, taken as directed and did not impair driving.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.