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AC- CNS lectures > Module 3.1.1 (Drugs for Treatment of Opiates Abuse) > Flashcards

Module 3.1.1 (Drugs for Treatment of Opiates Abuse) Flashcards

1
Q

What are the main opioids that lead to drug dependence and addiction?

A
  • Morphine Heroin Codeine Oxycodone
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2
Q

What is most commonly abused illicit opioid? What are its effects when it enters the brain? What happens with long term use?

A

Heroin –> structurally known as diacetylmorphine

  • Highly potent and water soluble –> injected IV
  • Heroin more lipid soluble than morphine hence enters CNS more rapidly
  • Rapidly enters brain –> euphoria / rush
  • Significantly reduced by first pass metabolism by liver, hence injection and inhalation are preferred means of administration by illicit drug users
  • Long term use –> tolerance and physical dependence
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3
Q

What are the acute effects of opioids?

A
  • Analgesia
  • Respiratory depression
  • Euphoria
  • Relaxation and sleep
  • Tranquilization
  • Decreased blood pressure
  • Constipation
  • Pupil constriction
  • Hypothermia
  • Drying of secretions
  • Reduced sex drive
  • Flushed and warm skin
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4
Q

What drug treatment is used for opioid overdose? What other uses do they have? What are some adverse effets?

A

Naloxone and naltrexone

> NALTREXONE = long half life and DOA

  • Reverse opioid-induced respiratory depression and analgesia
  • Improve breathing of babies of mothers treated with opioid during labour

Adverse effects

  • Precipitate withdrawal symptoms in particular naloxone
  • Reversal of analgesic effect of opioids
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5
Q

What are some properties of naloxone?

A
  • Pure competitive opioid receptor antagonist
  • Affects all three types of opioid receptors
  • Short T1/2 1-4 h
  • Much higher affinity for receptors than most opioid agonists

Use to reverse respiratory depression in opioid OD

  • IV – immediate recovery –highly effective = give parenterally
  • Caution –relapse as short half-life
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6
Q

What are some special considerations for naloxone?

A

Clients receiving naloxone should be observed for 2-3 h after treatment to ensure no relapse

  • Esp for methadone OD - long T1/2 (>24H)

Can reverse respiratory depression and sedation BUT NOT adverse effects of metabolites of opioids

> eg. seizures with norpethidine

> eg. cardiac dysrhythmias with nordextropropoxyphene

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7
Q

What are some properties of naltrexone? What to be cautious with?

A
  • Like naloxone - competitive opioid antagonist

> higher affinity to kappa compared to naloxone

  • Longer T1/2 10-12 h
  • Adjunct to management of opioid withdrawal/dependence
  • Tolerance to opioids is dramatically reduced – major risk of OD and death if naltrexone tm ceased and heroin is restarted
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8
Q

What are some withdrawal signs of opioids?

A
  • Pain and irritability
  • Painting and yawning
  • Dysphoria and depression
  • Restlessness and insomnia
  • Fearfulness and hostility
  • Increased blood pressure
  • Diarrhea
  • Pupil dilation (mydriasis)
  • Hyperthermia
  • Tearing, runny nose
  • Spontaneous ejaculation
  • Chilliness and gooseflesh
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9
Q

What is used for management of opioid withdrawal?

A

Buprenorphine

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10
Q

What are the TWO types of opioid dependence? Explain what the symptoms are and when they happen.

A

psychological dependence (First 12 h after withdrawal)

  • nervousness, sweating and craving

physiological (physical) dependence (thereafter)

  • dilated pupils, anorexia, weakness, depression, insomnia, gastrointestinal and skeletal muscle cramps, increased respiratory rate, pyrexia, piloerection with goose-pimples, and diarrhoea
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11
Q

Compare time course for development and symptoms between morphine and methadone.

A
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12
Q

Compare heroin with methadone

A
  • Heroin is fast-acting - after intravenous administration, generating a rapid “high,” - falls quickly leading to withdrawal symptoms –> short half life
  • Methadone is slow-acting with long half-life drug - asymptomatic over 24 hours
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13
Q

Tolerance is a decrease in initial pharmacologic effect after chronic or long-term administration, explain the following terms in regards to tolerance:

A) Associative (learned) tolerance

B) Non-associative (adaptive) tolerance

C) Cross Tolerance

D) Opioid rotation

A

A)

  • psychological component involved

B)

  • Due to down-regulation of opioid receptors

> also increase in firing of NA pathway

C)

  • Tolerance to analgesia, euphoria, respiratory depression and emesis
  • Less or No tolerance to miosis and constipation

D)

Opioid rotation may overcome some problems with tolerance

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14
Q

What is used for long-term management of opioid dependence?

A
  • Methadone
  • Buprenorphine
  • Naltrexone
  • Buprenorphine + naltrexone
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15
Q

How is methadone maintenance done?

A

Long-term substitution of oral methadone for heroin and other opioids - effective in reducing illicit opioid use

  • The methadone dose needs to be determined individually, taking into account the amount of opioid used before commencement and the initial response to methadone
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16
Q

How is buprenorphine maintenance done? Why does it lower overdose risk?

A

partial agonist activity gives it a lower overdose risk and lesser physical dependence compared to methadone, but the lower agonist activity is not suitable for some patients.

17
Q

How is naltrexone maintenance done?

A

Naltrexone is a long-acting, orally effective opioid antagonist. Useful for those illicit opioid users who are committed to abstinence.

18
Q

Compare methadone (agonist), buprenorphine (partial agonist), naltrexone (antagonist) for long term management of opioid dependence

A
19
Q

Describe the properties of methadone. Compare it to morphine.

A

Used mainly as substitute for heroin and morphine addicts

  • Similar effects to morphine but fewer withdrawal symptoms and less adverse effects

Long T1/2 >24h

  • High affinity for opioid receptors (on mu receptors only)
  • Reduce immediate “high” of heroin
  • Not suitable for acute pain as long T1/2
    *
20
Q

Describe properties of buprenorphine

A

Partial opioid agonist, reduce abuse potential

  • Has both agonist and antagonist properties
  • agonist at mu receptor, antagonist at kappa receptor and thus blocks dysphoric effects of opioids
  • A very potent opioid analgesic
  • Bioavailability sublingual > oral
  • Long T1/2 12h
  • High hepatic first pass
  • Bioavailability sublingual > oral, given sublingually
  • More marked dizziness and nausea – limits use
  • Respiratory depression not easily reversed by naloxone

> valuable for terminal cancer pain

21
Q

Explain when buprenorphine plus naloxone is used

A

Suboxone (Buprenorphine + naloxone)

  • Naloxone is included in combination tablets to discourage IV use
  • Little clinical effect when used sublingually
  • If these tablets are injected, naloxone will antagonise the effects of other opioids
  • May cause some withdrawal symptoms

AC- CNS lectures (28 decks)

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