ADDICTION: MOM - Agonist & Agonistic Substitution

Question 1

Agonist Meaning

Answer 1

A chemical that binds to and activates a response from a postsynaptic receptor

• With reference to medication; they are designed to imitate the action of other drugs e.g. Heroin
• E.g. Methadone

Question 2

Antagonist Meaning

Answer 2

A chemical that binds to and blocks the function of a particular substance

• Typically used in the abstinence stage of addiction recovery
  
  • Blocks euphoric and pleasurable feelings associated with opioids - makes them less desirable
• E.g. Naltrexone

Question 3

Methadone as a treatment for addiction

Answer 3

• Aims to reduce cravings for and withdrawal symptoms of heroin
• Has some of the same effects as heroin but does not give users the same ‘high’
• The dosage should be reduced over time (detoxification) until it is no longer needed (abstinence)
• It is recommended that methadone treatment is given alongside psychological treatment
• Doctor / nurse / pharmacist sees patients daily for the first 3 months of methadone treatment
  
  • Supervision is required to ensure the patient does not take multiple doses at once or sell their methadone to other users
• Usually given orally as a green liquid though can be given in different forms (tablet / injection)
  
  • Giving methadone orally helps reduce the risk associated with needle and injection use

Question 4

Methadone Dosage

Answer 4

UK NICE guidelines recommend an initial dosage of 10-40mg daily; increased by up to 10mg daily until withdrawal and toxification symptoms are not seen (National Institute for Health and Care Excellence)

• Individual receives a maintenance dose of 60-120mg daily

Question 5

Methadone: What is it?

Answer 5

Agonist Substitution

Used as a part of maintenance treatment

Question 6

Naltrexone: What is it?

Answer 6

Antagonist Substitution

Oral medication - available as an implant / depot injection (only approved in USA and Russia)

Question 7

Naltrexone as a treatment for addiction

Answer 7

• Can be offered as a therapy for opioid addiction and alcohol addiction
• It is recommended that naltrexone treatment is given alongside psychological treatment
• Can be used up to a 6 month period
• Users should be supervised to ensure they have not started drinking again
• Has been suggested by NHMRC in Australia that it could be used for problem gamblers though more research is needed

Question 8

Naltrexone Use

Answer 8

UK NICE guidelines recommend naltrexone is given to those who are opioid free and demonstrate high motivation to sustain abstinence from drugs (National Institute for Health and Care Excellence)

Question 9

Addiction: Agonist & Antagonist Substitution :)

Answer 9

Methadone’s Effectiveness: NICE / Van Den Brink & Haasen

Methadone & Criminality: National Treatment Agency Report

Question 10

Addiction: Agonist & Antagonist Substitution :(

Answer 10

Comparing Methadone to buprenorphine: Marteau et al.

Effectiveness of Naltrexone: NICE / Lahti et al.

Ethical criticisms of Methadone

Side effects of Naltrexone

Question 11

Addiction Agonist & Antagonist Substitution :) Methadone’s Effectiveness

Answer 11

NICE assessed 31 reviews of methadone’s effectiveness including 27 randomised controlled trials as a part of their guidance on its use
- Higher levels of retention for methadone users than placebo or no treatment
- Lower rates of illicit opioid use

Van Den Brink & Haasen - Meta-analysis of studies into the effectiveness of a range of treatments concluded that as long as the dosage is adequate then methadone is effective as a maintenance treatment

Question 12

Addiction Agonist & Antagonist Substitution :) Methadone & Criminality

Answer 12

National Treatment Agency Report - Treating heroin users with methadone reduces criminality (🙂 4 society)
- Suggest that rates of offending are reduced by half when addicts are in treatment

Centre for Policy Studies Report - Claimed that drug-related offending has continued to rise despite the availability of drug treatments such as methadone

Question 13

Addiction Agonist & Antagonist Substitution :( Comparing Methadone to Buprenorphine

Answer 13

Buprenorphine - a milder alternative to methadone
- Agonist & antagonist properties
- Activates opioid receptors to produce an opiate effect (agonist) but also blocks the euphoria (antagonist)
:) - Less risk of overdose due to ‘ceiling effect’
- After a certain amount has been taken any more will not increase the effect of the drug

Marteau et al. - Analysed data over a 5 year period; concluded that buprenorphine was 6x safer than methadone

Question 14

Addiction Agonist & Antagonist Substitution :( Effectiveness of Naltrexone

Answer 14

A NICE research review of 17 studies shows conflicting results on the effectiveness of naltrexone on the treatment of heroin addiction

• No significant difference found between naltrexone and control treatment for retention
• When results were pooled, naltrexone was associated with reduced relapse rates

Question 15

Addiction Agonist & Antagonist Substitution :( Ethical Criticisms of Methadone

Answer 15

• Side effects of methadone
  
  • Methadone may interact with other drugs ( alcohol / antidepressants) to cause respiratory issues
  • Danger of overdose when combined with other drugs
  • ONS reports that methadone was responsible for 429 deaths in the UK
• Critics highlight that all methadone achieves is creating a new addiction
  
  • Many individuals remain on methadone treatment for prolonged periods of time
  • Without the right support users will struggle to make it to the detoxification and abstinence stage

Question 16

Addiction Agonist & Antagonist Substitution :( Side Effects of Naltrexone

Answer 16

• Greater risk of overdose
  
  • If individual returns to addictive drug; they will need more of it to achieve the same effect; therefore more likely to overdose
  • Users with liver issues will need to be monitored carefully as if they are still opioid dependent naltrexone can cause withdrawal symptoms (antagonist treatment)