Analgesics Flashcards

1
Q

Pain acute/nociceptive

A

short-term pain, with an easily identifiable cause. A warning of present damage to tissue or disease which responds well to medication.

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2
Q

Pain chronic/neuropathic

A

pain which persists. Is constant or intermittent and has “outlived its purpose” since it no longer help the body to prevent further injury.

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3
Q

Pain allodynia

A

pain from a stimulus that does not normally cause pain

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4
Q

Pain parasthesis

A

painful feelings (e.g. pins & needles) with no apparent stimulus

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5
Q

Pain management - general considerations

A
Assessments
Type of pain (nociceptive versus neuropathic)
Form of pain (acute versus chronic)
Severity of pain 
Route of administration 

Objectives
Best analgesic for the individual
Lowest effective dose
Least invasive route - topical, oral, sublingual, i.v., i.m., i.p., i.t., epidural

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6
Q

Opioids – Mechanism of Action

A

Act at the level of the spinal cord and the CNS:
Decrease neurotransmitter release
Block postsynaptic receptors
Activate inhibitory pathways

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7
Q

Opioids – side effects

A

Dose-related; from nausea, vomiting, constipation, drowsiness, to respiratory depression, hypotension, sedation, dependency

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8
Q

opioids cautions/contradictions

A

Acute respiratory depression, acute alcoholism, head injury

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9
Q

opioids interactions

A

alcohol - hypotensive and sedative effects
MAOI - CNS excitation/inhibition
SSRI / TCA - sedation
carbamazepine -plasma conc. of methadone
cimetidine (ulcer healing) - inhibit opioids metabolism

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10
Q

SSRI

A

Selective serotonin reuptake inhibitor

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11
Q

TCA

A

Tricyclic antidepressants

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12
Q

Opioids neuropharmacology

A

-Mimic Our Endogenous Ligands “enkephalins”
β-Endorphin; Leu-enkephalin;
Met-enkephalin; dynorphin

-Signal Transduction
G-protein coupled receptors

-Integrated Physiology
“act as suppressors..”

-Act as Agonists at Opioid Receptors
Three types of receptors: m, k, d
Six sub-types: m, k1,2,3: d1,2

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13
Q

Opioid receptor - delta

A

CNS & Peripheral Sensory Neurons

May contribute to analgesia

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14
Q

opioid receptor - μ

A

CNS, Spinal Cord,
Peripheral Sensory Neurons, GI Tract
Responsible for most of the analgesic effects
Responsible for side effects
Most analgesic opioids are μ-receptor agonists

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15
Q

opioid receptor - kappa

A

CNS, Spinal Cord, Peripheral Sensory Neurons
Sedation & dysphoria, but few side effects
Does not contribute to dependence

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16
Q

Opioids Pharmacodynamics

Pure Agonists

A

Typified by morphine-like drugs

Have high affinity for μ-receptors; low affinity for δ & κ

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17
Q

Opioids Pharmacodynamics

Partial agonists & Mixed Agonist-Antagonists

A

e. g. nalorphine: mixed effects on μ-receptors

e. g. pentazocine & cyclazocine: (-) at μ-, but partial (+) on δ- & κ-

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18
Q

Opioids Pharmacodynamics

Antagonists

A

Block the actions of opiates

e.g. naloxone and naltrexone; treatment of heroin/morphine overdose

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19
Q

Morphine

A
Oral; i.v.; Intrathecal; subcutaneosly
Acute & Chronic pain
pharmacokinetic t1/2=3-4 h 
side effects:
Sedation, Respiratory depression, Constipation, Nausea,  vomiting,  Itching,  Tolerance, Dependence, Euphoria
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20
Q

Diamorphine

A

Oral;i.v.
Acute & chronic pain
Pharamacokinetic - More rapid than morphine; metabolised to morphine. Has a greater solubility
side effects:
Sedation, Respiratory depression, Constipation, Nausea, vomiting, Itching, Tolerance, Dependence, Euphoria

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21
Q

Hydromorphone

A
Oral; i.v.
Acute & chronic pain 
Pharamacokinetic -t 1/2= 2-4 h
side effects:
same as morphine but less sedative, despite being 6 fold more effective
22
Q

Methadone

A
Oral; i.v.
chronic pain 
Pharamacokinetic - Long t1/2= > 24 h Slow onset
side effects
same as morphine but ↓ euphoric
23
Q

Pethidine

A
Oral; i.v.; intramuscular 
Acute Intense pain
t1/2= 2-4 h Rapid acting
side effects
same as morphine but anticholinergic effects
Risk of excitement and convulsions
24
Q

Buprenorphine

A

i.v. Sublingual, Intrathecal, transdermal,
Moderate to severe. Acute or chronic. Peri-operative analgesia. iv; postoperative pain
t1/2= ~ 12 h Slow onset.
side effects
same as morphine but less pronounced. Respiratory depression not (-) by naloxone

25
Q

Pentazocine

A

Oral; i.v.
Moderate to severe pain.
t1/2= 2-4 h
Dysphoria; Irritation at injection site.

26
Q

Fentanyl

A

i.v.; Epidermal; Transdermal patch
acute pain
t1/2= 2-4 h
side effects same as morphine

27
Q

Codeine

A
Oral 
mild pain
Prodrug and metabolised to morphine 
side effects:
Mainly constipation; No dependence liability
28
Q

Tramadol

A

Oral i.v.
Acute & chronic pain
Rheumatoid arthritis, restless legs syndrome, motor neurone disease, fibromyalgia.
Well absorbed Half-life 4-6 h
side effects
Dizziness; May cause convulsions; No respiratory depression

29
Q

Antidepressants & Analgesia; Mechanism of Action

A

Serotonin and noradrenaline mediate descending inhibition of ascending pain pathways in the brain and spinal cord

30
Q

Serotonin and Noradrenaline Reuptake Inhibitors

SNRI

A

Highly effective for neuropathic pain, but not in all patients
Actions are independent of their antidepressant effects
Venlafaxine (Effexor, Efexor)
Duloxetine (Cymbalta, Ariclaim, Xeristar, Yentreve, Duzela)

31
Q

Selective serotonin reuptake inhibitors

SSRI

A

Not particularly effective analgesics
Appear to work well in the disease environment, e.g. diabetic- or HIV-related neuropathy e.g. paroxetine, citalopram
Paroxetine (Aropax, Paxil, Pexeva, Seroxat, Sereupin)
Citalopram (Celexa,Cipramil)

32
Q

SNRI/SSRI Mode of Action

A

Prevent the recycling of neurotransmitters & enhance the signal..

33
Q

Duloxetine

A

Prescribed for peripheral neuropathy, particularity diabetic neuropathy.
Side-effects include nausea, somnolence, insomnia, dizziness

34
Q

Venlafaxine (Effexor, Efexor)

A

Prescribed for diabetic neuropathy

Side-effects include nausea, sedation, headache and dizziness.

35
Q

SNRI & SSRI Antidepressants & Analgesia cautions and contradictions

A

Epilepsy, cardiac disease, diabetes, angle closure glaucoma, pregnancy / breast feeding

36
Q

SNRI & SSRI Antidepressants & Analgesia interactions

A

Alcohol - sedation
NSAIDS / aspirin -risk of bleeding
Tramadol - risk of CNS toxicity
Increase in sedative effectiveness when given with opioid analgesics
SSRI’s antagonise anticonvulsant effect of antiepileptics

37
Q

Antiepileptic Agents – Mechanism of Action

A
Inhibit of voltage gated Na+ channels 
Inhibit of voltage gated Ca2+ channels
Inhibit Glutamate, g-Aminobutyric Acid (GABA) & Glycine receptors
- Inhibit action potential firing
- prevent impulse transmission
- limit neuronal excitation
- enhance neuronal inhibition
38
Q

Carbamazepine treatment for

A

glossopharyngeal neuralgia, post herpetic neuralgia, trigeminal neuralgia, and diabetic neuropathies

39
Q

Carbamazepine side effects

A

Dizziness, diplopia, drowsiness, fatigue, nausea, hepatotoxicity, renal impairment, skin reactions, anorexia, dyspepsia, tremor

40
Q

Carbamazepine cautions and contraindictions

A

hepatic / renal impairment, cardiac disease, skin reactions, glaucoma, pregnancy, history of bone marrow depression.
alcohol - increase CNS side effects of carbamzepine
antagonised by MAOI, TCA, SSRI

41
Q

Gabapentin treatment for

A

various neuropathic pain states;
complex regional pain syndrome, deafferentation neuropathy of the face, postherpetic neuralgia, sciatic type pain, neuropathy

42
Q

Gabapentin side effects

A

+ anorexia, dyspepsia, tremor

43
Q

Gabapentin cautions and contraindictions

A

elderly, renal impairment, diabetes, pregnancy,

44
Q

MAOI

A

Monoamine oxidase inhibitors

45
Q

Local Anaesthetics – Mechanism of Action

A

Inhibit of voltage gated Na+ channels or NMDA receptors
Prevent nerve-nerve cell communication
- inhibit firing
- prevent impulse transmission

46
Q

NMDA receptor

A

glutamate receptor and ion channel protein found in nerve cells. It is activated when glutamate and glycine (or D-serine) bind to it, and when activated it allows positively charged ions to flow through the cell membrane.

47
Q

Lidocaine (Xylocaine)

A

Particularly effective for severe intractable or crescendo neuropathic pain: emergency medicine
Na-Channel Blocker
Effective in non-cancer patients
IV

48
Q

Lidocaine (Xylocaine) side effects

A

CNS effects (confusion), respiratory depression, convulsions, hypotension, bradycardia

49
Q

Lidocaine (Xylocaine) cautions and contraindications

A

epilepsy, hepatic / respiratory impairment, Atrial fibrillation, heart block, heart failure

50
Q

Ketamine (Ketalar)

A

Particularly effective for severe intractable or crescendo neuropathic pain: emergency medicine
Blocker of Glutamate Receptors (NMDA Subtype).
injectable but not favourable due to side effects

51
Q

Ketamine (Ketalar) side effects

A

Hypertension, tachycardia, tremor, diplopia, myocardial depression

52
Q

Ketamine (Ketalar) Cautions / Contraindications

A

Hypertension, angina, heart failure, aneurysms, cerebral trauma, psychotic disorders