Episode 21

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Published on:

23rd Dec 2021

Methadone pharmacokinetics and interactions

Episode 21 of Cracking Addiction explores methadone pharmacokinetics, breakdown and interactions within the body and interactions with other drugs.

Methadone is a drug with a wide variability in its absorption with oral bio-availability ranges from 35% to 100%. This is a significant amount of variability and explains why the same dose of Methadone can impact different patients differently.

Methadone is metabolised within the liver by the cytochrome P450 enzymes but mainly 3A4. There is a 17-fold inter-individual variation of methadone blood concentration for a given dosage and variations in metabolism account for a large part of this variation. Kinetic interactions influenced by the CYP 450 enzyme can affect plasma methadone levels.

• Inducers of CYP450 can

• Accelerate the metabolism of methadone

• lower methadone plasma levels

• Precipitate opioid withdrawal

• Inhibitors of CYP450 can

• Slow the metabolism of methadone

• Increase plasma levels

• Produce opioid toxicity (sedation, overdose)

Methadone is excreted renally with approximately 10% of drug renally eliminated unchanged. Renal excretion of methadone urinary pH dependent with increased Methadone excretion noted at pH less than 6 and decreased Methadone excretion at higher pH levels.

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About the Podcast

Cracking Addiction
Cracking Addiction Podcast
Welcome to Cracking Addiction, the show that delves deep into the world of addiction medicine. Hosted by Addiction Medicine Specialist Dr Ferghal Armstrong, this podcast covers a broad range of addiction-related topics, from the science behind addiction to the various treatment options available.


Each week, the hosts provide listeners with engaging and informative discussions on all aspects of addiction medicine. From alcohol and drug addiction to gambling addiction, they explore the various types of addiction and their impact on individuals, families, and communities.


With a focus on evidence-based information, Cracking Addiction provides listeners with a comprehensive understanding of addiction, including the latest research and treatment options. Whether you are struggling with addiction or simply interested in learning more about the topic, this podcast is an excellent resource.


The show also features regular guests and experts who share their insights and experiences on addiction-related topics.

With new episodes released every week, Cracking Addiction is your go-to source for the latest information and insights on addiction medicine. So join us as we explore this complex and fascinating topic and work to break the cycle of addiction.


Visit our website for more information and free courses https://go.meducate.com.au/courses

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Dr Ferghal Armstrong

Dr Ferghal Armstrong is a general practitioner, Addiction Medicine Specialist (FAChAM), accredited MATOD trainer as well as the CEO and co-founder of Meducate