1. Name Of The Medicinal Product
Methadone 5 mg/ml Oral Solution
2. Qualitative And Quantitative Composition
Each 1 ml of solution contains 5 mg of methadone hydrochloride
Also contains the excipients:
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Liquid Maltitol (E965)
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550.00 mg/ml
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Sunset Yellow (E110)
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0.01 mg/ml
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For a full list of excipients, see section 6.1.
3. Pharmaceutical Form
Oral solution
Clear, light amber coloured solution
4. Clinical Particulars
4.1 Therapeutic Indications
For use in the treatment of opioid addiction as an opioid abstinence syndrome suppressant, within a broader treatment protocol/programme, accompanied by regular reviews and reassessment. This treatment must be supervised by specialist services.
4.2 Posology And Method Of Administration
For oral administration only.
This product is not intended for dilution; therefore information pertaining to the compatibility of diluents is not available.
This product must not be injected.
Dosage should be titrated to the individual needs of patients.
Dosage Recommendations
The usual initial dose is 10-30 mg. For patients with high opioid tolerance, the initial dose is 25-40 mg. The dose is increased in steps of 10 mg at a time over a period of three weeks, usually to 70 or 80 mg. After a recommended stabilisation period of four weeks, the dose is adjusted, until the patient, does not have a need for intoxication and is without clinical signs of psychomotor function effects or abstinence symptoms.
The usual dose is 60-120 mg of methadone per day, but some individuals may require higher doses. The dosage should be determined based upon clinical assessment supported by serum level monitoring. The recommended steady state 24 h serum level is 600-1200 nmol/l (200-400 ng/ml). Great importance is attached to the clinical assessment.
Methadone is normally administered once daily. If administered more frequently, there will be a risk of accumulation and overdose. The highest recommended dose, that rarely should be used, is 150 mg/day (unless national guidelines recommend otherwise). The reason for this dose limitation is an increased frequency of QT-prolongation, Torsades de Pointes and cases of cardiac arrest within higher dose ranges (see section 4.4). High doses may also elicit low-grade (but unwanted) euphoria during a couple of hours after the daily dose.
In patients concomitantly treated with CYP3A4 inducers, higher doses than 150 mg may be required (e.g. HIV patients). Since the inducing effect is highly variable, doses above 150 mg should only be administered with caution (see section 4.4 and 4.5).
Patients should be observed in relation to dose increases to discover unwanted reactions. The patient obtains an increased serum level for up to two hours, and it is important that signs of overdose or other serious/unpleasant reactions are discovered.
Some patients develop auto-induction, which leads to the medication being more rapidly metabolised in the body. In such cases, the dose must be increased once or more to maintain the optimal effect.
If the patient has been treated with a combined agonist/antagonist (e.g. buprenorphine), the dose should be reduced gradually when the methadone treatment is initiated. If the methadone treatment is interrupted and a switch to sublingual buprenorphine treatment is planned (especially in combination with naloxone), the methadone dose should be reduced to 30 mg/day initially to avoid withdrawal symptoms caused by buprenorphine/naloxone.
Caution must be exercised after administration to elderly or ill patients. Methadone must not be administered to children (see section 4.3). Patients with hypothyroidism, myxedema, urethral stricture, asthma or decreased lung volume or prostatic hypertrophy must receive a lower initial dose.
Hepatic impairment:
Caution should be exercised when this product is used in patients with liver impairment. In patients with liver cirrhosis the metabolic breakdown of methadone is delayed and the first-pass effect is reduced. This may result in higher methadone plasma levels. This product should be administered at a dose lower than that usually recommended and the patient's response should be used as a guideline for further dosage requirements.
Renal impairment:
Caution should be exercised in the use of methadone in patients with renal impairment. The dose interval should be lengthened to a minimum of 32 hours if the glomerular filtration rate (GFR) is 10 – 50 ml/min and to a minimum of 36 hours if the GFR is lower than 10 ml/min.
If treatment has to be discontinued, this should be done by gradual dose reduction. The dose may be reduced relatively rapidly in the beginning, but reduction must be slow in the final phase (from 20 mg daily and downwards).
Elderly: In case of elderly or ill patients repeated doses should only be given with extreme caution
Children: Not recommended for children.
4.3 Contraindications
1. Respiratory depression, obstructive airways disease
2. Hypersensitivity to methadone hydrochloride or any of the ingredients of the product.
3. Concurrent administration with M.A.O. inhibitors or within 2 weeks of discontinuation of treatment with them. Concurrent use of other central nervous system depressants.
4. Use during an acute asthma attack is not recommended.
5. Obstetric use not recommended, because in labour the prolonged duration of action increases the risk of neonatal respiratory depression. Methadone is not suitable for children (see section 4.2 and 5.2). Babies born to mothers receiving methadone may suffer withdrawal symptoms.
6. Head injury and raised intracranial pressure.
7. Acute alcoholism
8. Individuals with QT prolongation, including congenital long QT syndrome (see section 4.4)
9. Methadone should be used with caution in patients with Hypothyroidism, adrenocortical insufficiency, prostatic hyperplasia, hypotension, shock, inflammatory or obstructive bowel disorders or myasthenia gravis.
10. As with all opioid analgesics, this product should not be administered to patients with severe hepatic impairment as it may precipitate Porto-systemic Encephalopathy in patients with severe liver damage.
As with other opioid drugs, methadone may cause constipation which is particularly dangerous in patients with severe hepatic impairment and measures to avoid constipation should be initiated early.
4.4 Special Warnings And Precautions For Use
1. The symptoms and signs of overdosage and toxicity of methadone are essentially those for morphine, though it is said that methadone has a greater respiratory depressive effect and a lesser sedative effect than an equianalgesic dose of morphine. Toxic doses are highly variable, regular usage giving tolerance. Pulmonary oedema is a frequent corollary of overdosage whilst the dose-related histamine-releasing property of methadone may account for at least some of the urticaria and pruritis associated with methadone administration. Methadone may lead to an increase in intracranial pressure.
2. Adverse effects occurring more rarely in patients being treated for opioid addiction are as follows:
(a) A number of heroin patients have been reported to die within a few days of starting a methadone maintenance programme. Evidence of chronic persistent hepatitis was detected in ten heroin patients, who died within 2-6 days of starting methadone treatment. The mean prescribed dose at the time of death was about 60mg. It has been suggested that these sudden deaths may have arisen as a result of accumulation of methadone over several days resulting in death from complications such as cardiac arrhythmias or cardiovascular collapse as methadone, like dextropropoxyphene, has membrane stabilising activity and can block nerve conduction.
In view of the possibility of reduced clearance and raised plasma levels it is recommended that liver function tests and urine tests be carried out prior to maintenance and that lower starting doses of methadone be used.
(b) Evidence of hypoadrenalism has been found in chronic methadone patients. Findings consistent with both deficient ACTH production and subsequent secondary hypoadrenalism and methadone induced primary adrenal cortical hypofunction have been reported.
(c) Choreic movements involving the upper limbs, torso and speech mechanisms have been reported in a 25-year-old man receiving methadone hydrochloride maintenance therapy (45-60 mg/day) for 2 years. Discontinuation of methadone resulted in complete alleviation of the abnormal movements with no recurrence during the subsequent eight months.
(d) The function of the secondary sex organs was found to be markedly impaired in 29 male participants in a methadone maintenance programme. The ejaculate volume and seminal vesicular and prostatic secretions in subjects maintained on methadone (mean daily dose 66.9 mg) were reduced by over 50% compared to 16 heroin patients and 43 opioid-free controls. Serum testosterone levels were also approximately 43% lower in those on methadone. Whilst the sperm counts of the methadone users were more than twice the control level, reflecting a lack of sperm dilution by secondary sex organ secretion, the sperm motility of these subjects was markedly lower than normal.
3. Cases of QT-interval prolongation and torsade de pointes have been reported during treatment with methadone, particularly at high doses (>>100mg/d). Methadone should be administered with caution to patients at risk for development of prolonged QT interval, e.g. in case of:
• history of cardiac conduction abnormalities
• advanced heart disease or ischaemic heart disease, known history of QT prolongation
• liver disease
• family history of sudden death
• electrolyte abnormalities (hypokalaemia, hypomagnesaemia)
• concomitant treatment with drugs that have a potential for QT-prolongation
• concomitant treatment with drugs which may cause electrolyte abnormalities
• concomitant treatment with cytochrome P450 CYP 3A4 inhibitors (see section 4.5)
• In patients with recognised risk factors for QT-prolongation, or in case of concomitant treatment with drugs that have a potential for QT prolongation, ECG monitoring is recommended prior to methadone treatment, with a further ECG test at dose stabilisation. ECG monitoring is recommended, in patients without recognised risk factors for QT prolongation, before dose titration above 100mg/d and at seven days after titration.
4. Sunset Yellow (E110) may cause allergic reactions.
5. This product contains liquid maltitol (E965). Patients with rare hereditary problems of fructose intolerance should not take this medicine.
Children are more sensitive than adults and intoxication may follow a low dose intake of methadone. To avoid such intoxication following dose administration by mistake, methadone should be kept in a safe place out of reach by children when located at home.
4.5 Interaction With Other Medicinal Products And Other Forms Of Interaction
Pharmacokinetic interactions
P-glycoprotein inhibitors: Methadone is a substrate of p-glycoprotein; all medicinal products that inhibit P-glycoprotein (e.g. qunidine, verapamil, ciclosporin), may therefore raise the serum concentration of methadone. The pharmacodynamic effect of methadone may also increase because of increased blood brain barrier passage.
CYP3A4-enzyme inducers: Methadone is a substrate of CYP3A4 (see section 5.2). By induction of CYP3A4, clearance of methadone will increase and the plasma levels decrease. Inducers of this enzyme (barbiturates, carbamazepine, phenytoin, nevirapine, rifampicine, efavirenz, amprenavir, spirononlactone, dexamethasone, Hypericum perforatum (St John's Wort), may induce hepatic metabolism. For instance, after three weeks treatment with 600 mg efavirenz daily, the mean maximal plasma concentration and AUC decreased by 48 % and 57 % respectively, in patients treated with methadone (35-100 mg daily).
The consequences of enzyme induction are more marked if the inducer is administered after treatment with methadone has begun. Abstinence symptoms have been reported following such interactions and hence, it may be necessary to increase the methadone dose. If treatment with a CYP3A4 inducer is interrupted, the methadone dose should be reduced.
CYP3A4-enzyme inhibitors: Methadone is a substrate of CYP3A4 (see section 5.2). By inhibition of CYP3A4 clearance of methadone is lowered. Concomitant administration of CYP3A4 inhibitors (e.g. cannabinoids, clarithromycin, delavirdine, erythromycin, fluconazole, grapefruit juice, itraconazole, ketoconazole, fluoxetine, fluvoxamine, nefazodone and telithromycin) may result in increased plasma concentrations of methadone. A 40-100 % increase of the quote between the serum levels and the methadone dose has been shown with concomitant fluvoxamine treatment. If these medicinal products are prescribed to patients on methadone maintenance treatment, one should be aware of the risk of overdose.
Products that affect the acidity of the urine: Methadone is a weak base. Acidifiers of the urine (such as ammonium chloride and ascorbic acid) may increase the renal clearance of methadone. Patients that are treated with methadone are recommended to avoid products containing ammonium chloride.
Concomitant HIV infection treatment: Some protease inhibitors (amprenavir, nelfinavir, lopinavir/ritonavir and ritonavir/saquinavir) seem to decrease the serum levels of methadone. When ritonavir is administered alone, a two-fold AUC of methadone has been observed. The plasma levels of zidovudin (a nucleoside analogue) increase with methadone use after both oral and intravenous administration of zidovudin. This is more noticeable after oral than after intravenous use of zidovudin. These observations are likely caused by inhibition of zidovudine glucuronidation, and therefore decreased clearance of zidovudin. During treatment with methadone, patients must be carefully monitored for signs of toxicity caused by zidovudine, why it may be necessary to reduce the dose of zidovudin .Because of mutual interactions between zidovudin and methadone (zidovudine is a CYP3A4 inducer), typical opioid abstinence symptoms may develop during concomitant use (headache, myalgia, fatigue and irritability).
Didanosine and stavudine: Methadone delays the absorption and increases the first pass metabolism of stavudine and didanosine which results in a decreased bioavailability of stavudine and didanosine.
Methadone may double the serum levels of desipramine.
Pharmacodynamic interactions
Opioid antagonists:
Naloxone and Naltrexone counteracts the effects of methadone and induces abstinence.
CNS depressants: Medicinal products with a sedative effect on the central nervous system may result in increased respiratory depression, hypotension, strong sedation or coma, therefore it may be necessary to reduce the dose of one or both of the medicinal products. With methadone treatment, the slowly eliminated substance methadone, give rise to a slow tolerance development and every dose increase may after 1-2 weeks give rise to symptoms of respiratory depression. The dose adjustments must therefore be made with caution and the dose increased gradually with careful observation.
Peristalsis inhibition: Concomitant use of methadone and peristalsis inhibiting medicinal products (loperamide and diphenoxylate) may result in severe obstipation and increase the CNS depressant effects. Opioid analgesics, in combination with antimuscarinics, may result in severe obstipation or paralytic ileus, especially in long-term use.
QT-prolongation: Methadone should not be combined with medicinal products that may prolong the QT interval such as antiarrhytmics (sotalol, amiodarone, and flecainid), antipsychotics (thioridazine, haloperidol, sertindo, and phenotiazines), antidepressants (paroxetine, sertraline) or antibiotics (erythromycin, clarithromycin).
MAO-inhibitors: Concomitant administration of MAO-inhibitors may result in reinforced CNS-inhibition, serious hypotonia and or apnoea. Methadone should not be combined with MAO-inhibitors and two weeks after such treatment (see section 4.3).
Opioid analgesics delay gastric emptying, thereby invalidating test results. Delivery of technetium Tc 99m disofenin to the small bowel may be prevented and plasma amylase and plasma lipase activity may increase because opioid analgesics may cause constriction of the sphincter of Oddi and increased biliary tract pressure; these actions result in delayed visualization and thus resemble obstruction of the common bile duct. The diagnostic utility of determinations of these enzymes may be compromised for up to 24 hours after the medication has been given. Cerebrospinal fluid pressure (CSF) may be increased; effect is secondary to respiratory depression – induced carbon dioxide retention.
4.6 Pregnancy And Lactation
Pregnancy:
Limited data on the use of methadone in pregnancy in humans show no elevated risk of congenital abnormalities. Withdrawal symptoms / respiratory depression might occur in neonates of mothers that were treated with methadone chronically during pregnancy. Data from animal studies have shown reproduction toxicity (see section 5.3). It is generally advisable not to detoxify the patient, especially after the 20th week of pregnancy, but to administer maintenance treatment with methadone. The use of Methadone oral solution just before and during birth is advised against because of the risk of neonatal respiratory depression.
Lactation:
Methadone is excreted in breast milk and the average milk/plasma ratio is 0.8. Breast feeding may be given on doses of up to 20mg per day. At higher doses the benefits of breast feeding must be weighed against the possible adverse effects on the infant.
4.7 Effects On Ability To Drive And Use Machines
Methadone will affect the psychomotor functions until the patient has been stabilised at a suitable level. The patient should therefore not drive or use machines until stabilisation has been achieved and there have been no symptoms of abuse for the last six months. When, driving and use of machines can be resumed, is largely dependent on the individual patient and must be determined by the physician. For further information see the national guidelines for methadone treatment.
4.8 Undesirable Effects
The undesirable effects of methadone treatment are in general the same as when treated with other opioids. The most common side effects are nausea and vomiting that is observed in approximately 20 % of the patients that go through methadone outpatient treatment, where the medicinal control is often unsatisfactory.
The most serious side effect of methadone is respiratory depression, which may emerge during the stabilisation phase. Apnoea, shock and cardiac arrest have occurred.
Adverse reactions listed below are classified according to frequency and system organ class. These side effects are more frequently observed in non opioid-tolerant individuals. Frequency groupings are defined according to the following convention: Very common (
System organ class MedDRA
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Frequency
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Adverse event
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Investigations
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Common
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Weight increase
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Metabolism and nutrition disorders.
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Not known
Common
Uncommon
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hypokalemia, hypomagnesemia
Fluid retention
anorexia
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Blood and lymphatic system disorders
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Not known
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reversible thrombocytopenia has been reported in opioid patients with chronic hepatitis
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Respiratory, thoracic and mediastinal disorders
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Uncommon
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pulmonary oedema, respiratory depression
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Gastrointestinal disorders
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Very common
Common
uncommon
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nausea, vomiting
obstipation
xerostomia, glossitis
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Psychiatric disorders
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Common
Uncommon
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euphoria, hallucinations
dysphoria, agitation, insomnia, disorientation, reduced libido
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Ear and labyrinth disorders
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Common
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Vertigo
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Eye disorders
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Common
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Blurred vision, miosis
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Nervous system disorders
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Common
Uncommon
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sedation
headache, syncope
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Skin and subcutaneous tissue disorders
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Common
Uncommon
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transient rash, sweating
pruritus, urticaria, other rash and in very uncommon cases bleeding urticaria
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General disorders and administration site conditions
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Common
Uncommon
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fatigue
oedema of the lower extremities, asthenia, oedema
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Hepatobiliary disorders
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Uncommon
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bile duct dyskinesia
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Vascular disorders
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Uncommon
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facial flush, hypotension
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Cardiac disorders
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Rare
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bradycardia, palpitations, cases of prolonged QT intervals and “torsade de pointes” have been reported in treatment with methadone, especially with high doses.
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Renal and urinary disorders
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Uncommon
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Urinary retention and antidiuretic effect
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Reproductive system and breast disorders
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Uncommon
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Reduced potency and amenorrhea
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In long term use of methadone, as for maintenance treatment, the undesirable effects diminish successively and progressively during a period of several weeks however, obstipation and perspiration often remain. Long-term use of methadone may lead to morphine-like dependence. The abstinence syndromes are similar to the ones observed with morphine and heroine, however less intense, but more long-lasting.
4.9 Overdose
The symptoms and signs of overdosage and toxicity of methadone are essentially those for morphine, though respiratory depression may be more profound and prolonged than for an equivalent dose of morphine. Severe overdose is characterised by respiratory failure, extreme drowsiness that develops into stupor or coma, maximum pupillary constriction, skeletal-muscle flaccidity, cold and clammy skin and occasionally bradycardia and hypotension. Apnoea, cardiovascular failure, cardiac arrest and death may occur in serious cases of overdose, especially in intravenous administration.
Treatment is supportive and use of an opioid antagonist such as naloxone, malorphine or levallorphan should be limited to those patients with demonstrated respiratory or cardiovascular depression due to methadone.
Naloxone is the preferred antagonist as there is less likelihood of further respiratory depression from the effects of the opioid antagonist. Use of an opioid antagonist may need to be continued for up to 48 hours due to the duration of action of methadone, and for this reason respiratory and cardiovascular monitoring is mandatory. Dialysis, CNS stimulation and respiratory stimulants are contraindicated. Acidification of the urine will increase the renal clearance of the drug.
5. Pharmacological Properties
5.1 Pharmacodynamic Properties
Pharmacotherapeutic group: Drugs used in opioid dependence
ATC code: N07BC02
Methadone is an opioid analgesic in the same manner of morphine and like morphine is highly addictive drug in its own right. It has a less sedative effect than morphine. It acts on the CNS system and smooth muscle. This action is caused by the response of structurally and sterically specific opiate receptor sites in the brain, spinal cord and nervous system.
Methadone is an opioid agonist with actions predominantly at the µ receptor. The analgesic activity of the racemate is almost entirely due to the l-isomer, which is at least 10 times more potent as an analgesic than the d-isomer. The d-isomer lacks significant respiratory depressant activity but does have anti-tussive effects. Methadone also has some agonist actions at the κ and σ opiate receptors. These actions result in analgesia, depression of respiration, suppression of cough, nausea and vomiting (via an effect on the chemoreceptor trigger zone) and constipation. An effect on the nucleus of the automotor nerve and perhaps on opioid receptors in the pupillary muscles causes pupillary constriction. All these effects are reversible by naloxone with a pA2 value similar to its antagonism of Morphine. Like many basic drugs, Methadone enters mast cells and releases histamine by a non-immunological mechanism. It causes a dependence syndrome of the Morphine type.
5.2 Pharmacokinetic Properties
Absorption: methadone is rapidly absorbed following oral administration, but undergoes considerable first-pass metabolism. The bioavailability is above 80 %. Steady state concentrations are reached within 5-7 days.
Distribution: distribution volume: 5 L/kg. Protein binding: up to 90 %, but with great individual differences. Methadone binds mainly to alpha1-glycoprotein acid, but also to albumin and other plasma and tissue proteins. Plasma: the full blood ratio is around 1:3. It is distributed to tissue with higher concentrations in the liver, lungs and kidneys than in the blood.
Metabolism: catalysed primarily by CYP3A4, but CYP2D6 and CYP2B6 are also involved, but to a smaller extent. Metabolism is mainly N-demethylisation, which produces the most important metabolites: 2-ethylidine, 1,5-dimethyl-3,3 -diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrrolidine (EMDP), which are both inactive. Hydroxylation to methanol succeeded by N-demethylisation to normethadol also occurs to some extent. Other metabolic reactions also occur, and at least eight other metabolites are known.
Elimination: elimination half-life: single dose: 10-25 hours. Repeated doses: 13-55 hours. Plasma clearance is around 2 ml/min/kg. About 20-60 % of the dose is eliminated in urine over 96 hours (about 33 % in unmodified form, about 43 % as EDDP and about 5-10 % as EMDP). The ratio between EDDP and unmodified methadone is usually much higher in urine in patients receiving methadone treatment compared to normal overdoses. Elimination of unmodified methadone in urine is pH-dependent and increases with increasing acidity of the urine. About 30 % of the dose is eliminated in faeces, but this percentage will normally be reduced at higher doses. About 75 % of overall elimination is unconjugated.
Special populations
There are no significant differences in the pharmacokinetics between men and women. The clearance of methadone is decreased only to some extent in elderly (>65 years).
Because of increased exposure, caution is advised in the treatment of patients with renal and hepatic impairment (see sections 4.2 and 4.4).
5.3 Preclinical Safety Data
Methadone at high doses caused birth abnormalities in marmots, hamsters and mice, in which most reports were of exencephaly and defects in the central nervous system. Rachischisis in the cervical region was found occasionally in mice. Non-closure of the neural tube was found in chicken embryos. Methadone was not teratogenic in rats and rabbits. A reduced number of young was found in rats and increased mortality, growth retardation, neurological behavioural effects and reduced brain weight were found in the pups. Reduced ossification of the digits, sternum and skull was found in mice and a smaller number of fetuses per litter. No carcinogenicity studies have been carried out.
6. Pharmaceutical Particulars
6.1 List Of Excipients
Hydroxyethylcellulose
Propylene glycol
Benzoic acid (E210)
Sodium hydroxide
Liquid maltitol (E965)
Sunset yellow (E110)
Purified water
6.2 Incompatibilities
None known
6.3 Shelf Life
Amber glass and PET bottles:
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48 months
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HDPE bottles:
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24 months
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In-use shelf life:
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60 days
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6.4 Special Precautions For Storage
Do not store above 25°C. Keep the bottle in the outer carton in order to protect from light.
6.5 Nature And Contents Of Container
Type III amber glass bottle with tamper evident CRC cap and a LDPE liner containing 100ml, 200ml, 300ml, 500ml or 1L.
PET bottles with tamper evident CRC cap and a LDPE liner containing 100ml, 200ml, 300ml or 500ml.
HDPE bottles with tamper evident CRC cap and an LDPE liner containing 14 ml, 16 ml, 18 ml, 20 ml, 22 ml, 24 ml, 26 ml, 28 ml, 30 ml, 32 ml, 34 ml, 36 ml, 38 ml, 40 ml, 42 ml, 44 ml, 46 ml, 48 ml or 50 ml.
Not all pack sizes may be marketed. These pack sizes should be used by healthcare professionals only.
6.6 Special Precautions For Disposal And Other Handling
For UK market only: Methadone hydrochloride is a controlled drug under the Misuse of Drugs Act SI 12 of 1977.
In Sweden, the larger pack sizes (>30 ml) should be handled by healthcare professionals only
7. Marketing Authorisation Holder
Pinewood Laboratories Limited,
Trading as Pinewood Healthcare,
Ballymacarbry,
Clonmel,
County Tipperary,
Ireland
8. Marketing Authorisation Number(S)
PL 04917/0111
9. Date Of First Authorisation/Renewal Of The Authorisation
14/01/2011
10. Date Of Revision Of The Text
01/09/2011
