Methadone


Thông tin thuốc gốc
Chỉ định và Liều dùng
Oral
Opioid dependence
Adult: Initially, 10-40 mg daily, may increase in increments of 5-10 mg to a max weekly increase of 30 mg. Dosage must be individualised and adjusted to keep withdrawal symptoms at a tolerable level.

Oral
Severe pain
Adult: For pain management that is opioid responsive and requires daily, continuous and long-term treatment: 2.5-10 mg 6-8 hourly.

Parenteral
Severe pain
Adult: For pain management that is opioid responsive and requires daily, continuous and long-term treatment: 2.5-10 mg 6-8 hourly via IM/SC/IV inj.

Parenteral
Opioid dependence
Adult: Initially, 10-40 mg daily, may increase in increments of 5-10 mg to a max weekly increase of 30 mg. Doses are given via IM/SC/IV inj. Dosage must be individualised and adjusted to keep withdrawal symptoms at a tolerable level.
Suy thận
Dosage adjustment may be needed.
Suy gan
Dosage adjustment may be needed. Severe: Contraindicated.
Cách dùng
May be taken with or without food.
Hướng dẫn pha thuốc
Dispersible tablet: Dissolve the tablet in approx 120 mL of water, orange juice, or any acidic fruit drink.
Chống chỉ định
Severe respiratory depression, bronchial asthma (in the absence of resuscitative equipment or with unmonitored settings), hypercabia, known or suspected gastrointestinal obstruction, paralytic ileus, ulcerative colitis, biliary or renal tract spasm, increased intracranial pressure, head injury, acute alcoholism, severe hepatic impairment; patient under coma. Concurrent use of or within 14 days of discontinuing MAOIs.
Thận trọng
Patient with CV disease (e.g. acute MI, cardiac hypertrophy), hypovolaemia, COPD, adrenocortical insufficiency (e.g. Addison’s disease), seizures, delirium tremens, mental health disorders (e.g. depression, anxiety disorders, posttraumatic stress disorder), psychosis, prostatic hyperplasia, thyroid dysfunction, electrolyte imbalance (e.g. hypokalaemia, hypomagnesaemia). Elderly, debilitated, and obese patients. Renal and hepatic impairment. Pregnancy and lactation. Avoid abrupt withdrawal.
Tác dụng không mong muốn
Significant: QT prolongation, serious arrhythmias (e.g. torsade de pointes), severe hypotension, serotonin syndrome, constipation, secondary hypogonadism leading to mood disorders and osteoporosis (long term use), severe elevation of intracranial pressure, seizures, sleep related disorders (e.g. central sleep apnoea [CSA], hypoxaemia), Oddi constriction.
Ear and labyrinth disorders: Vertigo.
Eye disorders: Blurred vision, miosis.
Gastrointestinal disorders: Nausea, vomiting, dry mouth.
General disorders and administration site conditions: Fatigue, injection site pain, erythema, and swelling.
Investigations: Increased weight.
Metabolism and nutrition disorders: Fluid retention.
Nervous system disorders: Sedation, dizziness, drowsiness, light-headedness, confusion.
Psychiatric disorders: Euphoria, hallucinations.
Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, diaphoresis.
Potentially Fatal: Respiratory depression.
IM/IV/Parenteral/PO/SC: C
Thông tin tư vấn bệnh nhân
This drug may cause drowsiness, if affected, do not drive or operate machinery.
Chỉ số theo dõi
Screen patient for any physical or psychological dependence before treatment. Obtain baseline ECG and monitor for QTC prolongation. Routinely check blood pressure, CNS status, respiratory status, and degree of sedation. Assess for signs of misuse, abuse, or addiction, respiratory depression, and serotonin syndrome.
Quá liều
Symptoms: Respiratory depression, somnolence progressing to stupor or coma, pin-point pupils, skeletal muscle flaccidity, cold and clammy skin, bradycardia, hypotension, mydriasis with hypoxia; pulmonary oedema, apnoea, circulatory collapse, cardiac arrest, death. Management: Supportive treatment. For patients with clinically significant respiratory depression, administer IV opioid antagonists (e.g. naloxone). Acidify the urine to increase excretion. Perform ECG monitoring; check for respiratory function.
Tương tác
Increased serum concentrations with CYP3A4 inhibitors (e.g. clarithromycin, erythromycin, delavirdine, fluconazole, itraconazole, ketoconazole, fluoxetine, fluvoxamine). Decreased serum concentrations with CYP3A4 inducers (e.g. barbiturates, carbamazepine, phenytoin, nevirapine, rifampicin, efavirenz, amprenavir, spironolactone, dexamethasone). Increased risk of QT prolongation with antiarrhythmics (e.g. sotalol, amiodarone), antipsychotics (e.g. thioridazine, haloperidol, sertindole, phenotiazines), antidepressants (e.g. paroxetine, sertraline). Increased risk of serotonin syndrome with SSRIs, SNRIs and TCAs.
Potentially Fatal: Increased risk of CNS depression with MAOIs.
Tương tác với thức ăn
Increased CNS depressant effect with alcohol. Increased serum plasma concentration with grapefruit. Decreased serum plasma concentration with St John’s Wort.
Tác dụng
Description: Methadone is a diphenylheptane derivative opioid agonist that primarily acts on the μ receptor. It inhibits the ascending pain pathways, alters the perception of and response to pain, and causes a generalized CNS depression.
Onset: 0.5-1 hour (oral); 10-20 minutes (parenteral).
Duration: 4-8 hours (as single oral dose); 22-48 hours (as maintenance oral dose).
Pharmacokinetics:
Absorption: Readily absorbed from the gastrointestinal tract. Bioavailability: 36-100% (oral). Time to peak plasma concentration: 1-7.5 hours.
Distribution: Widely distributed in the body tissues, crosses placenta, and enters breast milk. Volume of distribution: 1-8 L/kg. Plasma protein binding: 60-90% mainly to α1-acid glycoprotein.
Metabolism: Metabolised in the liver via N-demethylation by CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6 into its inactive metabolites.
Excretion: Via urine (<10% as unchanged drug) and faeces. Terminal elimination half-life: 8-59 hours.
Đặc tính

Chemical Structure Image
Methadone

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 4095, Methadone. https://pubchem.ncbi.nlm.nih.gov/compound/Methadone. Accessed Dec. 21, 2020.

Bảo quản
Tab/oral solution: Store between 20-25°C. Oral concentrate/Solution for inj: Store between 20-25°C. Protect from light.
Phân loại MIMS
Thuốc giảm đau (opioid) / Thuốc hỗ trợ cai nghiện
Phân loại ATC
N07BC02 - methadone ; Belongs to the class of drugs used in the management of opioid dependence.
Tài liệu tham khảo
Anon. Methadone. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 28/08/2020.

Anon. Methadone. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 28/08/2020.

Buckingham R (ed). Methadone Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 28/08/2020.

Dolophine Tablet (West-Ward Pharmaceuticals Corp.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/08/2020.

Joint Formulary Committee. Methadone Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 28/08/2020.

Methadone Hydrochloride Concentrate (VistaPharm Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/08/2020.

Methadone Hydrochloride Injection, Solution (Mylan Institutional LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/08/2020.

Methadone Hydrochloride Solution (Atlantic Biologicals Corp.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/08/2020.

Methadone Hydrochloride Tablet (Cebert Pharmaceuticals, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/08/2020.

Methadone Pliva (DCH Auriga (Hong Kong) Ltd). MIMS Hong Kong. http://www.mims.com/hongkong. Accessed 01/09/2020.

Physeptone 1 mg/mL Oral Solution Sugar-Free (Martindale Pharmaceuticals Ltd). MHRA. https://products.mhra.gov.uk/. Accessed 28/08/2020.

Physeptone 25 mg/mL Solution for Injection (Macarthys Laboratoris Ltd). MHRA. https://products.mhra.gov.uk/. Accessed 28/08/2020.

Physeptone 5 mg Tablets (Macarthys Laboratoris Ltd). MHRA. https://products.mhra.gov.uk/. Accessed 28/08/2020.

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