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Pain and Analgesics . Dr Ian Coombes, Judith Coombes, Dr Lisa Nissan University of Queensland Schools of Medicine and Pharmacy Safe Medication Practice Unit, Queensland Health. The University of Queensland. Outline. What is pain Pain assessment Principles of Pain Management

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pain and analgesics

Pain and Analgesics

Dr Ian Coombes, Judith Coombes, Dr Lisa Nissan

University of Queensland Schools of Medicine and Pharmacy

Safe Medication Practice Unit, Queensland Health

The University of Queensland

outline
Outline

What is pain

Pain assessment

Principles of Pain Management

Drug therapies

Neuropathic Pain and adjuvant therapy

Role of the Pharmacist / other health professionals

slide3
You have been asked to recommend a patient’s analgesia including medication choice dose and duration…

What patient factors do you need to consider?

what is pain
What is Pain?

A signaling system : mechanical and nerve

Unpleasant sensory & emotional experience – IASP

A perception : unlike taste or hearing

cannot define independent of person experiencing it

Only know in pain by statements & actions

Pain is what the patient says “hurts”

slide5

Psychological Factors

Sex

Age

Cognitive Level

Previous Pain

Family Learning

Culture

Noxious Stimulus,

Tissue Damage

Pain Sensation

Situational Factors

Expectation

Control

Relevance

Emotional Factors

Fear

Stress

Anxiety

Frustration

slide6

Acute pain (e.g. sprain, surgery)

  • Limited duration
  • related specifically to an event or trauma
  • bodies’ natural “healing” process

Palliative Care

components of both

e.g. incident pain,

disease progression

  • Chronic pain
  • pain persists beyond time of healing
  • often no specific pathology identified
  •  changes in the CNS
  •  development of NP
  • complex interplay physical +psychological
  • Often - sleep disturbances, fatigue, depression, social withdrawal, and self-esteem issues +++
acute vs chronic
Acute vs Chronic

Acute Pain

Passive patient

Short term planning

“hands-on” Tx

Rest

PRN Tx (inc. Meds)

Resume usual life

Chronic Pain

Active patient

Long term planning

“hands-off” Tx

Activity

Regular Tx (inc.Meds)

Retraining, readjustment

examples of acute pain
Examples of acute pain

Acute post operative pain

Sprains and strains

Sports injuries

Period pain

Headaches

Toothache / dental

types of chronic pain
Types of chronic pain

Chronic back or neck pain

Total body pain

Chronic daily headaches

Musculoskeletal pain

Include: OA,RA, polymyalgia

Painful diabetic neuropathy (PDN)

Post-herpetic neuralgia (PHN)

Phantom limb pain

cancer pain 4 sources
Cancer Pain – 4 sources

Malignancy

E.g. infiltration of tumor, fractures

Treatment Pain

E.g. radiotherapy, mucositis

Debility

E.g. bed sores

Unrelated

E.g. history of underlying lower back pain

types of pain
Types of pain

mechanical

inflammatory

neuropathic

two main categories
Two Main categories

Nociceptive Pain

Pain due to stimulation of superficial or deep tissue pain receptors as a result of injury or inflammation

Neuropathic Pain

Pain due to dysfunction or primary lesion in the central or peripheral nervous system

patient assessment
Patient Assessment

Goal to individualise analgesic therapy

Assess patient characteristics:

assessment
Assessment
  • Pain History (LINDOCARRF)
    • Location
    • Intensity
    • Nature
    • Duration
    • Onset, Offset
    • Concomitants
    • Aggravating
    • Relieving
    • Radiating
    • Frequency
slide16

Verbal Rating Scale:On a scale of 1-10 ….. How would you rate your pain?Sometimes add – “where 10 is the worst ever and zero is no pain”

principles of analgesic prescribing
Principles of Analgesic Prescribing
  • Analgesic Ladder
  • Adjuvants -
    • TCA
    • Anti-convulsants
    • Anti-arrhythmic

STEP 3

  • NSAID
  • Non-opioid (paracetamol)
  • Strong Opioid (morphine, oxycodone)
  • Adjuvant Medication

STEP 2

STEP 1

  • NSAID
  • Non-opioid (paracetamol)
  • Weak Opioid (codeine, tramadol)
  • Adjuvant Medication
  • NSAID
  • Non-opioid (paracetamol)
  • Adjuvant Medication
paracetamol
Analgesic, antipyretic, Act centrally (PGs)

Not useful as an anti-inflammatory

FewSE if taken at therapeutic doses

Onset of effect 30 - 60 min

Dosing:

500 –1000mg QID Max 4g for adult

Paracetamol
paracetamol23
Paracetamol

Should be 1st line therapy

minor, non-inflammatory pain

As effective as aspirin/NSAID in relieving acute pain

Similar antipyretic actions to aspirin, NSAID

No. 1 choice mild to moderate pain in children

May be given chronically:

1g QID, or for example in people with OA

ALTERNATE Extended release: 1330mg TDS

paracetamol24
Paracetamol

Dosing in Children - Often under dosed!

Appropriate:

15mg/kg Q4H MAX 60mg/kg (community)

15mg/kg Q4H MAX 90mg/kg (hospital)

Can use in Combination with Ibuprofen

Careful with other OTC products

Esp. cough and cold medications

“cumulative paracetamol”

side effects
Side-effects

major risk: is poisoning with overdose

Paracetamol can damage the liver (mainly OD)

Risk of toxicity  - dehydrated, malnourished, alcohol (chronic)

Common: N/V, dizziness, sedation

Less common: headache, skin rash

*NOTE: paracetamol & NSAID can be used together

how do they work nsaid v cox2
How do they work? - NSAID v COX2

Arachidonic acid

Maintenance

Induced

COX-1

COX-2

NSAIDs

Coxibs

thromboxane / prostaglandins

prostaglandins

Primarily mediate

inflammation, pain & fever

Primarily support platelet function

Primarily protect GI mucosa

coxib withdrawal 2004
COXib Withdrawal 2004

Vioxx® withdrawn 2004  CV risk

MOA CV risk

COX-2 is the main source of the prostacyclin PGI2

PGI2 acts in opposition to thromboxane

TXA2 generated by COX-1

PGI2 = anti-clotting (anti-thrombotic)

TXA2 = pro-clotting (pro-thrombotic)

Therefore, inhibiting COX-2   PGI2 synthesis  “pro-thrombotic” effect (TXA2)  risk of MI, stroke

non steroidal anti inflammatory drugs nsaid
Non-Steroidal Anti-inflammatory Drugs (NSAID)

Analgesic, antipyretic

Antiinflammatory - several days dosing

must dose constantly at least several days

prnnot significant anti-inflammatory action

Onset of action / effect 30 – 60 min

difference in half-life and SE

NOTE:

elderly patients should not be on NSAID's with long half-lives

can be even more prolonged in elderly

nsaids caution
NSAIDs – Caution!
  • Major cause of ADEs and hospital admissions
  • use lowest effective dose for shortest possible time
  • use paracetamol as alternative or to reduce NSAID dose
  • COX-2 inhibitors
    • similar adverse effects to non-selective
    • increase risk of thrombotic events (stroke; MI)!
  • little difference in efficacy between NSAIDs
  • avoid aspirin < 18 yrs in viral illness (Reye’s syndrome)
  • elderly - increased risk of adverse effects
  • Continue only if effective. Avoid if possible!
how do opioids act
How do Opioids Act?

G-protein

G-proteins

2nd messenger

systems

  • Interact with specific cell-surface receptors in
    • CNS and PNS
    • other tissues (GIT, immune cells, other tissues)
pharmacological effects of opioid agonists
Pharmacological Effects of Opioid Agonists
  • Desired Action – analgesia
  • Unwanted actions
    • Analgesic tolerance
    • physical dependence
    • Respiratory depression
    • Nausea, vomiting sedation

Tolerance often develops

other unwanted effects
Other unwanted effects
  • Constipation
    • inhibition of GIT motility
    • slowing of oral-caecal transit times
    • Never forget laxatives
  • Endocrine effects
    • may alter male sex hormones in chronic dosing
    • Must monitor in chronic therapy
  • Neuro-excitatory SE
    • e.g. myoclonus, allodynia, seizures
      • very high doses

No tolerance

slide36

Opioids – Precautions

  • hypotension, shock
  • concomitant CNS depression
  • impaired respiration /↓ respiratory reserve
  • elderly
  • hepatic impairment
  • renal impairment
  • epilepsy/recognised seizure risk
  • biliary colic or surgery
what are opioids
What are Opioids?
  • Step 2 / 3 - Moderate to severe pain
  • Definite role in cancer + non-cancer pain
  • Mu, Kappa, Delta receptors
  • Many available
  • Typical SE profile
    • Nausea, Drowsiness, Respiratory Depression
    • Constipation, Sweating, Itch
  • Caution in hepatic and renal impairment
opioids what to do
Opioids – what to do?
  • Assess requirements – calculate dose
      • Conversion table as a guide (if on other opioids)
      • Can start on one Short Acting opioid and titrate
      • Conversion to SR / CR preparation when possible
  • Adding it up …..
      • If currently on multiple Tx - Use conversion table
      • E.g. convert all to oral morphine equivalent
opioids what to do39
Opioids – what to do? ******
  • Start low go slow …..
      • When converting between opioids
      • Reduce calculated total daily dose ~20-30%
  • Breakthrough (incident pain – esp. in cancer)
      • Calculate as: 1/6th – 1/12th of TDD
        • Or ~ 50% of the dose just given (if e.g. Q4H)
slide40

Oral Morphine equivalent

* 100mg tramadol ~ 60mg codeine ~ 10mg oral morphine

slide42

Regular vs PRN Analgesia

  • regular analgesia is better in setting of continuous pain
  • PRN only if pain intermittent and unpredictable
  • in most settings, pain is predictable
  • problems with using only PRN analgesia
    • dose prescribed by Dr/administered by nurse
    • patients don’t ask for medication
  • inadequate or infrequent dosing → unrelieved pain
  • keeping up with pain is easier than catching up with pain
  • prn dose = 1/6 →1/12 total regular daily dose
tramadol tramal
Tramadol (Tramal)

Centrally acting analgesic with a dual MOA

1st - opioid effects similar to morphine (mu)

Active Metabolite M1

M1 - 6x tramadol as analgesic, 200x binding

2nd - inhibit re-uptake ofNA / 5-HT

descending pain inhibitory pathway

Hepatic Metab. Via CYP 2D6 (P450)

similar to codeine

slide44
 doses in renal and hepatic impairment

50 – 100mg 4-6 hrs (Max 400mg) or SR equiv.

Interactions:

SSRI, TCA, carbamazepine, MAOI, warfarin ( INR)

Can cause serotonin syndrome by itself!

Start low – go slow ……. Short term use only!

Start on IR then (switch to SR if appropriate)

slide45

More serious ADR’s with tramadol

  • Australian Adverse Drug Reactions Bulletin - Volume 22, Number 1, February 2003

NNT > / = 50% relief 3.5 (2.4 to 5.9)

NNH = 7.7 (4.6 to 20)

neuropathic pain
Neuropathic Pain
  • Pain or abnormal sensations due to a dysfunction of, or damage to, a nerve or group of nerves
  • primarily peripheral nerves, although pain due to CNS damage (“central pain”) may share these characteristics
neuropathic pain47
Neuropathic Pain
  • Can be due to a central or peripheral component
  • Opioids not particularly effective
      • Post Herpetic Neuralgia: acute herpes zoster
      • Phantom Limb Pain
      • Postoperative Pain
      • Diabetic neuropathy
  • May be lancinating (shooting, stabbing)
  • non-lancinating (dull, aching)
  • burning (dysesthesia)
slide48

TREATMENTS FOR NEUROPATHIC PAIN

Antidepressants

Anticonvulsants

Opioids

Topical

agents

Eg.

CBZ

Gabapentin

pregabalin

Eg.

Tramadol

oxycodone

Eg.

Lidocaine patch

Capsaicin

Eg.

Amitriptyline

Desipramine

paroxetine

things to think about when reviewing prescriptions
Things to think about when reviewing Prescriptions
  • Regular dosing of pain medications
  • Dosage form issues
    • Crushing, breaking SR/CR
    • Appropriate level of breakthrough medication
  • Managing SE
    • Importance of laxative use
    • Increasing needs ? More breakthrough
  • Interactions ….. Watch OTC / complementary
monitoring making it work
Monitoring – making it work
  • Frequent assessment is essential
  • Important to maintain communication with
    • Doctor, patients, carers
  • Nursing staff and pharmacist ……
    • Monitor for response to therapy
      • Include increase in need
      • Change in pain “type” or “origin”
      • Change in severity
    • ADR / SE
      • Esp. laxatives with opioids
key messages
Key Messages
  • individualise analgesic therapy
  • choose analgesics judiciously
  • use multimodal analgesia
  • regular pain monitoring is critical to outcomes
  • regularly review and revise analgesic doses
  • adjust regular dose according to breakthrough usage
  • anticipate and manage analgesic-associated adverse events
  • avoid NSAIDs – major cause of morbidity/mortality!
  • avoid tramadol, dextropropoxyphene, pethidine