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MD4001 > Opioids > Flashcards

Opioids Flashcards

1
Q

What is the main problem with opioids ?

A

Highly addictive, subject to misuse and abuse

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2
Q

Define opium, opioid, and opiate.

A

Opium: Natural extract of the poppy Papaver somniferum. It contains morphine and other related compounds (e.g. codeine).

Opioid: any substance (natural or synthetic) that produces morphine like effects which are blocked by a morphine antagonist

Opiate: any naturally occurring opioid

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3
Q

What is the main action of opioids they are used for ?

A

Their analgesic action

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4
Q

Differentiate between strong and weak opioids (what distinguishes them?)

A

Weak opioids have a “ceiling effect” where escalation of the dose typically causes SE without improving analgesia

Strong opioids do NOT (higher dose = higher effect + higher SEs), and are pure mu agonists

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5
Q

What is the main difference between different opioids, other than wether they are weak or strong. G

A

Vary mainly by:

  • Duration of action
  • Potency
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6
Q

Identify an example of long lasting, and short lasting opioid.

A

SHORT-ACTING:
Remifentanyl (infusion, lasts for seconds to minutes, metabolised by plasma esterases)
Fentanyl

LONG-ACTING
Methadone (lasts about 24 hrs)

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7
Q

What is the standard starting dose for morphine ? for fentanyl ? Why such a difference ?

A

PARENTERAL
Morphine: 10 mg (0.1 mg/kg)
Fentanyl: 100 micograms (1- 2micrograms /kg)

ORAL
Morphine: 30mg (0.3mg/kg)
Fentanyl: N/A

Difference because fentanyl much more potent

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8
Q

What is one reason a patient may have to switch opioid ? How may we determine how much of the next opioid we need to give ?

A

If ORAL opioid, and need more, or can physically not take it, may have to switch.

There are equivalencies between different opioids (refer to slide 7).
If change from oral to IV opioid, need to reduce dose.

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9
Q

Identify the main strong, and weak opioids.

A 
STRONG
• Morphine 
• Oxycodone
• Diamorphine 
• Fentanyl
• Pethidine
• Remifentanil 
• Methadone

WEAK
Codeine
Dihydrocodeine
Tramadal

RELATED AGENTS
Loperamide

ANTAGONISTS
Naloxone
Naltrexone

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10
Q

What is the effect of most drugs in overdose on the pupils ? of opioids ?

A

In overdose, most drugs will give you dilated pupils

Opioids will give you pinpoint pupil

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11
Q

What is the class of drug of diamorphine ? What are its main indications ? Why isn’t it used more ?

A

Sem-synthetic opioid, more water soluble

Palliative care patients who requires large doses of opioids (can give this in a smaller V of fluid)

SE: More buzz (liable to misuse and abuse)

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12
Q

Identify a route of administration for fentanyl.

A

Transdermal patch

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13
Q

Identify side effects of Pethidine.

A

Anti-cholinergic side effects

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14
Q

What are the main indications for Naloxone and naltrexone ? State the route of administration of each.

A

Naloxone: acute opioid toxicity (injection)

Naltrexone: given to people who are drug free after addiction problem, to stay off drug (by mouth)

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15
Q

Describe the main indications of Loperamide amongst opioids, and its mechanism of action.

A

No analgesic effect

Action on myenteric plexus of gut, helpful in cases of diarrhea (will constipate you)

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16
Q

Identify a side effect of Tramadol.

A

Serotoninergic effects means can feel down if cease treatment.

17
Q

Identify the main administration routes for opioids, stating an example of indication where each may be appropriate).

A

IV

ORAL- (ideal for patients under treatment for cancer/ongoing care)

TRANSDERMAL PATCH- Fentanyl (absorbed through skin, may be used if patient is drowsy, or for patients with stable managed pain since absorption may vary) (can also be absorbed in oral mucosa)

CENTRALLY- In epidural or spinal anaesthetia, can put opioid with local anesthetic (at VERY low dose of opioid)

IM Injections

18
Q

Describe the process of absorption of oral opioids.

A

Most opioids are weak bases. In the stomach, they remain in ionised form, and are therefore poorly absorbed. They tend to be absorbed into the bloodstream in the intestine (pH allows them to be unionised), and subsequently head to liver where undergo first pass metabolism (into active compounds e.g. codeine or into active metabolites) by CYP450. They then enter systemic circulation.

Many opioids have active metabolites, which are excreted by kidneys (problematic if renal failure)

19
Q

What is the main problem associated with transdermal patches (e.g. for Fentanyl).

A

Absorption will cary depending on dilation of blood vessels to the skin. E.G. if fever, or hot water bottle over area then increased absorption, and if patient cold or skin perfusion impaired then decreased absorption and patient may become sore.

20
Q

Define patient controlled analgesia.

A

Patient is in control of amount of drug they use. Safety feature present so if patient too drowsy to press button, cannot give themselves another drug of dose.

21
Q

Identify an opioid which is actually a prodrug. How does it produce its effects ?

A

Codeine is a prodrug, and has no effects. It has to be metabolised into a morphine by the liver before it actually has effects.

Different groups metabolite it in different ways:

  • 10% of Caucasians are slow metabolisers
  • 30% Africans are ultrafast metabolisers

i.e. for given dose, Africans get much larger dose on average

22
Q

State the bioavailability of the following:

  • Morphine
  • Oxycodone
  • Fentanyl
  • Codeine
  • Tramadol
A
  • Morphine: 30%
  • Oxycodone: 70%
  • Fentanyl: 50% (lozenge)
  • Codeine: 60%
  • Tramadol: 70%
23
Q

Identify the main opioid receptors.

A
  • mu opioid peptide receptor (MOP)
  • Kappa (KOP)
  • Delta (DOP)
  • Nociception (NOP)
24
Q

Identify the main sites in the body where opioid act.

A

Opioid receptors are widespread but more densely found where there is nervous tissue involved in pain transmission.

Opioid receptors are found in:

  • PAG
  • Peripheral tissues
  • Peripheral afferent nerve terminals
  • Nociceptors in peripheral tissues
  • Cortex
  • Thalamus
  • Myenteric plexus
25
Q

Name the main endogenous opioids.

A

Encephalins, endorphins, dynorphins naturally act at opioid receptors

26
Q

How do opioids act, on a cellular level ?

A

Opioids act on G protein coupled receptors. As a result:

  • opening of K+ channel which will move to outside cells, and cell hyperpolarises
  • closing of Calcium channels (unable to get into cells and encourage release of NT).
  • inhibitory effect on conversion of ATP to cyclic AMP

Overall result = reduced NT release

27
Q

Identify the main actions of opioids on the body.

A

CNS:

  • Analgesia.
  • Sedative effect (most opioids)
  • Sense of euphoria
  • Effect on third nerve nucleus (give pinpoint pupils)

RESPIRATORY:
-Depressed respiratory rate (both rate and TV depressed, but rate more so, so minute volume decreases and PCO2 increases) (hence v toxic in overdose)
-Anti-tussive effect (cough can be significant problem
in ppl with lung tumors, and codeine will work well to suppress that cough)
-Intubated patient can tolerate tube in trachea better
-Bronchoconstriction (esp in asthma patients) due to histamine release for some opioids (e.g. Morphine, NOT fentanyl)

CV:

  • Direct effect on SA node
  • Decrease SNS drive (slows heart down, sometimes profoundly)
  • Peripheral vasodilation (some, not all, probably due to histamine release)

GI:
-Nausea and constipation (N/V patients tend to adapt to, but constipation, rarely get
patients developing tolerance to it)
-Direct action on chemoreceptor trigger zone, leading to increased vestibular sensitivity

SKIN
-Urticaria and profound itch (histamine release, especially for injected drug)

URINARY
-Urinary retention

OTHER
-Long term, can lead to immunosuppression (action on NK cells), may make patients with addiction problems
more vulnerable to infection (e.g. infective endocarditis)
-Endocrine changes (increase prod of ADH and decrease production of ACTH and prolactin)

28
Q

In which cases are the sedative effects of opioids unfavorable ?

A

If cancer patient, and want pain controlled but want to go about ADLs, able to drive, think clearly etc.
it can have negative effects

29
Q

How is the respiratory depression effect of opioids mediated ?

A

Mediated by the brain, by mu receptors on brainstem

30
Q

Why does constipation occur in opioid use ?

A

Happens because of delayed motility (leading to full stomach, nausea, constipation)

31
Q

Identify other drugs which should be prescribed alongside opioids, and explain why.

A

Anti-emetic and anti-laxatives due to effects of opioids on GI

32
Q

Identify an opioid which has active metabolites. Which opioid should we use in patients with renal impairment ?

A

Morphine

Fentanyl is drug of choice in renal impairment

33
Q

To what extent can codeine be prescribed for children ? Why ?

A

CANNOT prescribe codeine to children, because of difference in metabolism between different people (pharmacogenetics)

34
Q

State the main principle of opioid prescribing in the elderly.

A

Titrate to effect (can be on lots of drugs which may interact with opioids, so incredibly small doses can have very potent effects, so start low and increase if needed)

35
Q

Why is it necessary to titrate up to effect with Naloxone ?

A

Because while the aim is to reverse respiratory depression and for person to breath again, do NOT want to make them sore

36
Q

What is the half life of Nolaxone ? What is the implication of this on treatment ?

A

Half life of naloxone about 45 minutes, shorter than a lot of opioids’ half life
(morphine half life is hours), so if manage to wake patient up, may have to start infusion of naloxone (to avoid patient returning to respiratory depression etc.)

37
Q

Define drug antagonist.

A

A drug with a high affinity for the receptor but no intrinsic activity

38
Q

What is the main indication for Methadone ? What are its main side effects ? How many doses do patients need in a day ?

A

Used for maintaining patients with addiction problem to opioids (prevent them taking street drugs).

Single dose in 24 hours (because long half life)

Side effects include negative effect on dental hygiene (present in viscous, sugary solution), dry mouth, cravings for sweet food, poor dentition.

39
Q

Identify legislation pertaining to the prescription of opioids.

A

Controlled drugs are covered by misuse of Drugs Act, 1971, drugs are under that according to the “harmfulness attributable to a drug when it is misused” (all strong opioids will be controlled drugs)

Misuse of Drugs Regulations 2001

Overall, must be very careful when prescribing opioids, as part of prescription very specific regulations (what exactly you have to write)

MD4001 (74 decks)

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