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Reporting of side effects
If you get any side effects, talk to your doctor or
pharmacist. This includes any possible side effects not
listed in this leaflet. You can also report side effects
directly via the Yellow Card Scheme (Website: www. By reporting side effects, you
can help provide more information on the safety of this

5. How Synastone 10mg/ml Injection
is stored
▪ Keep out of the reach and sight of children
▪ Do not store above 25ºC.
▪ Store in the outer carton and protect from light.
▪ Do not use Synastone Injection after the expiry date
which is stated on the ampoule and carton after
Exp:. The expiry date refers to the last day of that
▪ Medicines should not be disposed via wastewater
or household waste. Ask your pharmacist how to
dispose of medicines no longer required. These
measures will help to protect the environment.

6. Further information
Synastone Injection is a sterile solution for injection
containing Methadone Hydrochloride (10mg per ml).
It also contains Sodium Chloride and water.
The product is available in a number of volumes:
1ml (10mg Methadone Hydrochloride),
2ml (20mg Methadone Hydrochloride),
3.5ml (35mg Methadone Hydrochloride) and
5ml (50mg Methadone Hydrochloride) in packs of
10 ampoules.
The Marketing Authorisation for Synastone Injection
is held by Auden Mckenzie (Pharma Division) Ltd.
Mckenzie House, Bury Street, Ruislip, Middlesex,
HA4 7TL, UK.
Synastone Injection is manufactured by SNS
Pharmaceuticals Ltd., Mckenzie House, Bury Street,
Ruislip, Middlesex, HA4 7TL, UK.
This leaflet was updated in May 2015.


Synastone® 10mg in 1ml Solution for injection
Methadone Hydrochloride

This leaflet contains important information about Synastone 10mg/ml Injection.
Read all of this leaflet carefully before you start your treatment with this medicine.
1. Keep this leaflet. You may need to read it again.
2. If you have further questions, please ask your doctor.
3. If any of the side effects get serious, or if you notice any side effects not listed in this leaflet,
please tell your doctor or nurse.
In this leaflet
1. What is Synastone 10mg/ml Injection and what is it for
2. Before you are given Synastone 10mg/ml Injection
3. How Synastone 10mg/ml Injection is used
4. Possible side effects
5. How Synastone 10mg/ml Injection is stored
6. Further information

1. W
 hat is Synastone 10mg/ml
Injection and what is it for
Synastone belongs to a group of medicines called
It is used:
 s part of the treatment of addiction to opium
related drugs.
 s a pain killer (an analgesic) to relieve moderate to
severe pain when morphine may not be suitable.

2. Before you are given Synastone
10mg/ml Injection
Synastone 10mg/ml Injection should not be used if
• t hink you are allergic (hypersensitive) to
Methadone or any of the other ingredients of
Synastone injection (see section 6: Further
Information). Signs of an allergic reaction include:
a rash, itching, swallowing or breathing problems,
swelling of your lips, face, throat or tongue.
• s uffer from any illness which causes severe
breathing difficulties for example severe asthma.
 ave been told you have a tumour of the adrenal
gland near your kidney called phaeochromocytoma.
 re taking, or have taken in the last two weeks,
any of the antidepressant medicines called
monoamine oxidase inhibitors (MAOIs), including
• loss of consciousness.
• have a risk of paralysis of the intestine, perhaps after
abdominal surgery.
Always tell your doctor or nurse about any of these
before having your injection.

Take special care with Synastone 10mg/ml
 ecause it can be addictive.
 nly use the dose prescribed for you by your
doctor because higher doses could be fatal.
Without you knowing, the levels of the drug can
build up in your body and affect your breathing,
causing drowsiness and possible loss of
• if you have increased pressure on the brain or have
just had a head injury.
• if you are suffering from acute alcoholism.
• if you are suffering from mental illness brought on
by an infection
• if you have liver problems
• if you have kidney problems
• if you have problems with your bile duct
• if you suffer from an enlarged prostate gland
(in men) or have difficulty passing urine
• if you have an under-active thyroid or adrenal
• if you have low blood pressure
• if you are in a state of severe shock
• if you are very run down and feeling weak
• if you have bowel disease, such as Crohn’s disease
or ulcerative colitis
• if you suffer from convulsions (fits)
• if you are a child. Even at low doses methadone
is a special hazard to children if taken accidentally.
Children under 6 months, particularly newborns,
may be more sensitive to breathing difficulties
than adults
• if you are elderly
• if you have myasthenia gravis (a disorder that
causes extreme muscle fatigue)

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• if you suffer from certain types of heart disorders.
These types of heart disorder are usually
confirmed after an electrocardiogram (ECG) has
been performed and may be more likely to occur
with the following:
– if you have, or have had in the past any heart
disorder or disease.
– if you have liver disease
– if other members of your family have died
suddenly from unexplained causes.
– if you have reduced blood levels of potassium
or magnesium
– if you take particular medicines while you are
taking Synastone; please read the section
‘Taking/using other medicines’.
– if you are taking high doses of Synastone
(e.g. more than 100 mg per day).
Your doctor may wish to monitor you by doing an
ECG either before you start taking Synastone and/or
during treatment.
Injections may be painful; check the site of injection
regularly for swelling, reddening or itching.
Always tell your doctor or nurse about any of these
conditions or medicines before having your
Taking other medicines
Tell your doctor if you are taking or have recently
taken any medicines including medicines obtained
without a prescription. Synastone can interfere with
the action of some other drugs and some drugs can
have an effect on Synastone. The following drugs
can cause some problems when taken together
with Synastone Injection:
• s trong pain killers such as pethidine or codeine
 ntidepressants (fluoxetine, fluvoxamine, and other
SSRIs, tricyclic antidepressants),
sedatives and hypnotics (sleeping pills e.g.
benzodiazepines, chloral hydrate).
• s ome medicines used for heart disease or
medicines that can change your blood levels of
potassium or magnesium (e.g. diuretics), there
may be a greater risk of heart problems
 ntibiotics such as rifampicin, ciprofloxacin,
erythromycin or rifabutin.
 ntifungal drugs such as fluconazole,
ketoconazole or voriconazole.
 edicines to treat epilepsy (e.g. phenytoin or
• c ertain medicines for reducing stomach acid
(e.g. cimetidine)
 rugs which affect gastric emptying
(domperidone, metoclopramide)
 altrexone or naloxone blockade; buprenorphine
or pentazocine

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 edicines to change the acidity of your urine
such as vitamin C or sodium bicarbonate
 rugs used to treat the AIDS virus
 tropine and other muscle relaxants.
Taking Synastone injection with drink and food
 lcohol may interfere with the metabolism of
methadone and should be avoided.
 rapefruit juice may also interfere with
methadone metabolism; it is best not to consume
grapefruits or grapefruit juice.
Pregnancy and breast-feeding
 lways tell your doctor if you are pregnant,
think you might be pregnant or are trying to
become pregnant.
There is not enough evidence of safety of
methadone in pregnancy; for the benefit of both
you and your baby, you should seek the advice of
a doctor with appropriate experience so
specialized care can be arranged. Babies born to
mothers taking methadone may suffer withdrawal
 ethadone gets into breast milk; breast-fed
infants may develop their own physical
dependence on it. If breast feeding is considered,
your dose of Synastone should be as low as
possible and you should watch your baby closely
for any signs of excessive sleepiness. Remember
your baby could suffer withdrawal symptoms if you
either stop taking methadone or stop breast
feeding suddenly. Talk to your doctor so you
and your baby get the care required where
Driving and using machines
Synastone may make you feel sleepy. Do not drive
or operate any tools or machines as you may not be
The medicine can affect your ability to drive as it may
make you sleepy or dizzy.
 o not drive while taking this medicine until you
know how it affects you.
• It is an offence to drive if this medicine affects your
ability to drive.
 owever, you would not be committing an offence
• The medicine has been prescribed to treat
a medical or dental problem and
• You have taken it according to the
instructions given by the prescriber or in
the information provided with the medicine and
• It was not affecting your ability to drive safely.
Talk to your doctor or pharmacist if you are not sure
whether it is safe for you to drive while taking this

3. How Synastone 10mg/ml Injection is
Synastone will be given to you as an injection under
the skin or into a muscle.
Repeated injections should preferably be given into
a muscle, but volumes greater than 2ml (20mg)
may need to be injected in divided doses at different
For drug addiction:
The usual dose is 40-60mg a day but you will
probably be started on a lower dose of 10-20mg a
For the treatment of pain:
The usual dose is 5-10mg every 6-8 hours although
your doctor may decide to give you a different dose.
You may be prescribed a different dose if you are
elderly, have liver disease or are ill.
As methadone has not been studied in children, it
should not be used in children under the age of 16
If more Synastone is used than should be:
Contact your nearest hospital, doctor or pharmacist
You may feel sleepy, have problems breathing, feel
floppy and have cold, clammy skin and very small
It can also affect your heart and blood pressure.
It is important that you get to your nearest hospital
casualty department immediately.
If you miss a dose of Synastone
Do not take a double dose if you have missed one.
Take the missed dose as soon as you remember
and then ask your doctor or pharmacist when to
take the next dose.
If you are thinking about stopping or have recently
been told to stop Synastone
Do not suddenly stop taking it as you may get
unpleasant withdrawal symptoms. Your doctor will
tell you how long your treatment will last and how to
gradually stop taking it.
If you have any further questions on the use of this
product, ask your doctor or pharmacist.

4. Possible side effects
Like all medicines, Synastone can have side effects
although not everyone gets them.
One of the most serious and common side effect
(at higher doses) is slower breathing and can be
serious in that you may be unaware or too drowsy to
Other common side effects are:
▪ feeling or being sick
▪ constipation
▪ gallbladder disorder
▪ sleepiness
▪ feeling confused
▪ small pupils
▪ dry mouth, eyes and nose.
Less common side effects are:
▪ headache
▪ problems with passing water
▪ sweating
▪ flushing
▪ dizziness
▪ changes in your heart beat
▪ low blood pressure or body temperature
▪ lower sex drive and function
▪ changes in menstruation
▪ rashes
▪ restlessness
▪ changes of mood and
▪ hallucinations
▪ high blood levels of the hormone prolactin
▪ tense muscles
▪ fluid retention
▪ sleep disturbances
▪ visual disturbances.
You can become dependent on methadone.
In the case of serious side effects, patients should be
kept conscious wherever possible and an airway
established; artificial respiration may be necessary.
Repeated intravenous administration of appropriate
antidote medication (nalorphine or levallorphine) may
be required if there is evidence of significant breathing
difficulty. Oxygen, intravenous fluids, drugs to increase
blood pressure and other supportive measures should
be employed as necessary according to the severity of
the side effects.
If any of the side effects get serious, or if you notice
any side effects not listed in this leaflet, please tell
your doctor, nurse or pharmacist.

18/05/2015 10:49

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Further information

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