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Pharmacology > Opioids: Pharmacology, therapeutic uses, side effects > Flashcards

Opioids: Pharmacology, therapeutic uses, side effects Flashcards

1
Q

Where did opioid therapy originate from, and where is this origin extracted from?

A

Originates from opium

Which is extracted from seed capsules of opium poppies (papaver somniferum)

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2
Q

When opioid therapy was initially used, what were the 2 routes of administration?

A

Orally inhaled

Ingested

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3
Q

When opioid therapy was initially discovered, what 2 conditions was it used to treat?

A

Diarrhoea

Cough

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4
Q

When opioid therapy was initially discovered, what were the 3 main effects?

A

Recreational
Sedative
Analgesic

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5
Q

What instrument led to significant changes in the use of opioid therapy?

A

Hypodermic syringe and needle

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6
Q

What makes an synthetic opioid drug effective?

A

It has morphine-like effects

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7
Q

What are the 2 most commonly used opioid drugs?

A

Morphine
Codeine

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8
Q

Why are most pill forms of opioids given several times a day, but patches are not?

A

Pills have short half-life

Patch has much longer half-life, so lasts several days

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9
Q

Give 3 examples of alkaloids that are directly extracted from opium poppy, and describe this substance?

A

Directly extracted as white, milky latex substance

Morphine, thebaine, codeine

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10
Q

After alkaloids have been directly extracted from opium poppies, what are the 2 methods of further processing to obtain more morphine?

A

Alkaloids (white, milky latex substance) is purified to obtain more morphine

Other alkaloids processed to obtain morphine derivatives

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11
Q

Which 2 opioid drugs are produced from chemical modification of morphine?

A

Heroin
Codeine

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12
Q

Which 2 opioid drugs are produced from chemical modification of thebaine?

A

Oxycodone
Hydrocodone

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13
Q

What are the lab designs of synthetic opioid drugs based on, and give 3 examples?

A

Fentanyl, methadone, buprenorphine

Designs target opioid receptors

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14
Q

In the 1950s, what was discovered about the targeting/binding mechanism of opioid peptides?

A

Opioid peptide binds to different types of opioid receptor (G-coupled receptor), which are widely distributed in CNS and PNS eg. GI tract

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15
Q

What are the 3 opioid receptors that are widely distributed in the CNS and PNS?

A

Mu
Kappa
Delta

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16
Q

Which opioid receptor mostly causes respiratory side effects of opioid therapy, and give examples of other unwanted effects caused by this receptor?

A

Mu receptor

euphoria, respiratory depression, constipation, mental clouding, urinary retention, cough suppression

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17
Q

What is the desirable effect of opioid therapy that is induced by mu receptors?

A

Analgesia

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18
Q

Give 3 examples of opioid drugs that preferentially target mu receptors, and are these commonly or rarely prescribed?

A

Preferentially targeted by morphine, fentanyl, codeine (most commonly prescribed)

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19
Q

What is the desirable of effect of the kappa receptor targeted by opioid therapy, and give 3 unwanted side effects?

A

Binding to kappa receptor induces analgesia in periphery

Hallucinations, paranoia, dysphoria (unease and dissatisfaction)

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20
Q

What opioid receptor is preferentially targeted by ketocyclazocine?

A

Kappa receptor

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21
Q

What is the desirable effect of delta receptors targeted by opioids, and how was this discovered?

A

Delta receptor induces analgesia in spine

Discovered when delta receptors were found in vans deferens of mice

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22
Q

As well as exogenous opioids (eg. morphine, codeine), what other molecule can bind to opioid receptors to induce effects?

A

Opioid peptides which are produced by brain in response to physiologic stressors

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23
Q

Are opioid peptides structurally similar to other endogenous body peptides, and what is the characteristic feature of opioid peptides?

A

Yes

Characteristically have tyrosine at n-terminus

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24
Q

What are the 3 classes of naturally-occurring opioid peptides that are produced by the brain?

A

Beta-endorphins

Dynorphin (binds to Kappa receptor)

Leu-enkephalin, Met-enkephalin

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25
Q

Give 2 presentations of pain, for which morphine is the gold-standard opioid to prescribe?

A

Acute severe pain

Chronic pain in palliative care

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26
Q

Give 6 examples of administration routes for morphine?

A

Oral (PO)
IV
IM
Subcutaneous injection
Epidural
Intrathecal

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27
Q

Why do injections of morphine need to be given in lower dose then oral routes?

A

Injection releases quicker and more consistently

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28
Q

Are morphine liquids, tablets and capsules given PO (oral) only available in immediate-release formulations?

A

No, tablets and capsules are also available in extended-release formulations

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29
Q

After administration, how is morphine metabolised and how long is its half-life?

A

Morphine is broken down in liver to become active metabolite form morphine-6-glucuronide (strong analgesia), which has short half-life of 3-4 hours

Morphine-6-glucuronide eliminated in kidney

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30
Q

Why shouldn’t morphine be prescribed to patients with impaired renal function/dialysis?

A

Active metabolite morphine-6-glucuronide (strong analgesia) is eliminated in kidney

Impaired renal function/dialysis can cause metabolite to accumulate

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31
Q

Why is the short-half life of morphine and other opioid drugs problematic?

A

Shorter the half-life, the more of the drug a person may be tempted to take to treat their symptoms continuously, so more likely to develop tolerance

32
Q

What are the 4 CNS effects of morphine?

A

Pupil constriction (pin-point pupil)
Strong analgesia
Acute sedation
Euphoria

33
Q

What brain region causes the pupil constriction side effect of morphine and why?

A

Oculomotor nucleus in brainstem which gives rise to oculomotor/3rd cranial nerve which supplies intrinsic muscles for pupils

34
Q

What brain region do mu opioid receptor agonists such as morphine selectively bind to, in order to cause 2 common GI effects?

A

Selectively bind to mu receptors in the Chemical Trigger Zone (CTZ) in medulla

Induces nausea, acute vomiting

35
Q

How do side effects of limited mobility and muscle tightening commonly present, due to use of opioids?

A

Constipation

36
Q

Which 2 classes of drugs can be used to treat constipation and vomiting caused by opioid use?

A

Vomiting: Anti-emetic (vomiting) such as metoclopramide, ondansetron

Constipation: laxative such as senna

37
Q

Even though all opioid drugs have respiratory effects, why do mu opioid receptor agonists cause the largest degree of acute respiratory depression?

A

They selectively bind to mu receptors brainstem respiratory centres

38
Q

What are the 2 respiratory effects of morphine?

A

Acute respiratory depression
Cough suppression

39
Q

How does recurrent use of mu opioid receptor agonists cause tolerance?

A

Recurrent use of opioid drugs such as morphine can cause desensitisation of mu receptors, so increased doses are needed to achieve same degree of analgesia: tolerance

40
Q

What is the usual initial dose of morphine, and how can opioid tolerance be regulated?

A

starting dose 5-10 mg morphine

increase by 30-50% if no response, increase again by 30-50% if still pain recurs

review every few days

41
Q

When physical dependence on opioid drug has developed, when do withdrawal symptoms present and give 5 examples?

A

Withdrawal symptoms present when person stops taking drug abruptly

Restlessness, shivering, aggressiveness, diarrhoea, runny nose

42
Q

Describe the main feeling that develops when a person has psychological dependence on a opioid drug?

A

Craving for the drug which can last for months to years

43
Q

What is the IUPAC name of heroin/diamorphine?

A

3-6-diacetylmorphine

44
Q

Which opioid drug is heroin a prodrug of, and what are the 2 active metabolite forms that are produced from heroin?

A

Prodrug of morphine

Active forms: morphine, 6-monoacetylmorphine

45
Q

Does heroin have a high or low affinity for mu receptors, and why is heroin an effective prodrug?

A

Heroin has low affinity for mu receptors,

but it is converted to active forms morphine and 6-monoacetylmorphine which have high affinity for mu receptors

Therefore heroin is an effective prodrug

46
Q

When heroin/diamorphine is administered by IM injection, why is the dose 50% of the morphine dose that would have been used for IM injection?

A

Heroin is more lipid-soluble than morphine, so is more potent and has a more rapid onset

47
Q

What is the main effect of heroin when administered by IV injection, and why does this occur?

A

Heroin crosses blood-brain barrier easily when administered by IV injection

which provides rapid high

48
Q

Give 2 presentations of pain for which diamorphine/heroin is commonly used?

A

Chronic pain in palliative care, where high doses need to be given in small volume syringes

Postoperative pain after major surgery

49
Q

Is methadone a natural or synthetic opioid drug?

A

Synthetic opioid

50
Q

What is the half-life and bioavailability of methadone compared to morphine?

A

Methadone has much longer half-life (24-30hrs) but morphine is short (3-4 hrs)

Methadone has much higher bioavailability especially when administered orally (80% dose absorbed)

51
Q

Who uses methadone as substitution therapy and why, and why is it effective in a supervised regime?

A

IV users/addicts with Opioid Use Disorder (OUD) to reduce reduce IV morphine/heroin abuse

Can relieve withdrawal symptoms and reduce cravings for morphine/heroin

52
Q

Why must the time of administered doses of methadone be monitored very closely?

A

If methadone is administered too often, overdose can occur which is very toxic due to long half-life

53
Q

What is the most common route of administration of fentanyl and buprenorphine, and why?

A

Patch

Long-lasting so is more convenient than giving doses more often

54
Q

What is the IUPAC name of codeine?

A

3-methoxymorphine

55
Q

How is codeine converted to morphine?

A

Codeine (3-methoxymorphine) is demethylated in liver by CYP2D6 enzyme to morphine

56
Q

Why does codeine only induce moderate analgesia even though it is well-absorbed orally?

A

Only some is converted to morphine, so it has a much lower efficacy which results in moderate analgesia

57
Q

How does genetic variation influence an individual’s response to codeine?

A

Genetic variation of liver CYP enzymes causes unpredictable response to codeine

58
Q

If NSAIDs and paracetamol are both ineffective/unsuitable to prescribe to a patient, what opioid drug is prescribed?

A

Codeine

59
Q

How can the analgesic effect of a single dose of codeine be increased?

A

It is combined with ibuprofen, aspirin or paracetamol

60
Q

What 2 drugs is co-codamol a combination of?

A

Compound analgesic compromising codeine and paracetamol

61
Q

What 2 drugs is co-dydramol a combination of?

A

Compound analgesic compromising dihydrocodeine and paracetamol

62
Q

Is dihydrocodeine a natural or synthetic opioid, and what is the active form that it is metabolised to?

A

Semi-synthetic prodrug that is metabolised to dihydromorphine

63
Q

What pain intensity is dihydrocodeine prescribed for?

A

Mild-moderate pain

64
Q

What is dyspnea, and what opioid drug is prescribed for severe dyspnea?

A

Dyspnea: sensation of running out of the air, not being able to breathe fast/deeply enough

Treated by dihydrocodeine

65
Q

What is meant by dihydrocodeine having an antitussive effect?

A

Antitussive: cough suppressant

66
Q

Give 3 common side effects of codeine?

A

Constipation

Cough suppression

Severe toxicity in suspected children

67
Q

Should opioid receptor agonist drugs be prescribed for neuropathic pain?

A

No, as neuropathic pain is partially sensitive to opioids

Deafferentation pain: subdivision of neuropathic pain that occurs when somatosensory system is damaged and is insensitive to opioids

68
Q

Give 2 reasons why opioid therapy shouldn’t be prescribed for migraines and tension headaches?

A

Risk of dependency

Adverse effects such as medication overuse headaches

69
Q

Why shouldn’t opioid therapy be prescribed for low back chronic pain?

A

No proven significant clinical benefits, so can cause unnecessary side effects

70
Q

What is the most commonly used opioid antagonist drug?

A

Naloxone

71
Q

What is the mechanism of action of naloxone and other opioid antagonists drugs, in reversing the effects of morphine and other opioid agonist drugs?

A

Naloxone/opioid antagonist drug blocks mu receptors so that morphine/mu-receptor opioid agonist drug can’t bind, which reverses effect

72
Q

What is the route of administration of naloxone/opioid antagonist to reverse acute opioid toxicity?

A

Injection

73
Q

Give 5 side effects of naloxone/opioid antagonist drugs?

A

Breathing problems
Low oxygen stats
Drowsiness
Altered mental state
Small pupils

74
Q

What are the 2 formulations of naloxone that are available in the community?

A

Prenoxad (pre-filled syringe)

Nyxoid (nasal spray)

75
Q

Which 2 opioid antagonist drugs have peripheral action to prevent GI effects of morphine/opioid agonist drugs?

A

Methylnaltrexone, naloxegol

76
Q

What is naltrexone prescribed for in programmes?

A

Aids detox in opioid and alcohol withdrawal programmes

Pharmacology (13 decks)

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