Week 23 - pain conditions Flashcards by nat r

What is pain?

The International Association for the Study
of Pain (IASP) definition for pain:
an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage

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Acute pain

-Sudden onset - sharp or intense
-Serves as a warning sign of disease or threat to the body
-Caused by injury, surgery, illness, trauma, or painful medical procedures
-Lasts from a few minutes to less than 3 months
-Usually disappears whenever the underlying cause is treated or healed

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Analgesics

An analgesic is a medication used to reduce pain

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Anti-pyretic

Reduces body temperature
(fever)

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Anti-inflammatory

Reduces inflammation

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Paracetamol

Paracetamol inhibits the cyclooxygenase (COX) enzyme
->Child – suspension – easier to swallow and taste -> soluble tablets – easier to swallow and
absorbed more quickly
->Safe in pregnancy and breastfeeding
-Dose based on narrow age bands – not practical for consumers to calculate dose
based on body-weight (mg/kg)

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Uses for paracetamol

For mild to moderate pain e.g.
-Headache
-Migraine
-Toothache (refer if abscess)
-Dysmenorrhoea
-Fever
-Osteoarthritis
->Less GI irritation compared with NSAIDs

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Cautions for paracetamol

BNF – states appropriate sections for cautions and CI and interactions
-Risk factors for hepatotoxicity
->liver or kidney dysfunction
->Malnutrition, dehydration, alcohol misuse
->Older, frail patients
->Body weight<50kg, enzyme inducing medication
->Overdose – nausea and vomiting then liver failure (after 4-6 days)

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Paracetamol suspension

For mild to moderate pain and as an antipyretic
Suitable for children:
->From 2 months(=>4kg)
for post-immunisation
pyrexia
->From 3 months for fever
and pain
Shake the bottle before use (for min 10 secs)

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NSAID mechanism of action

Non-selective NSAIDs e.g. Ibuprofen, Aspirin, Naproxen, Diclofenac (topical)
->Inhibit prostaglandin (PG) synthesis by reversibly inhibiting cyclo-oxygenase
(COX) enzymes — COX-1 and COX-2
-COX-1 produces PG that help to maintain gastric mucosal integrity and platelet-initiated
blood clotting
-COX-2 produces PG that mediate pain and inflammation

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NSAIDs - cautions

-Asthma (can induce asthma attack in 10%) - class effect
-Kidney impairment (decreases renal function)
-Cardiovascular disease and hypertension
-Inflammatory bowel disease such as crohn’s or ulcerative colitis

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NSAIDs - contraindications

-Active peptic ulceration or GI bleeding
-Severe heart, renal or liver failure
-Pregnancy – non-selective NSAIDs contraindicated after 30 weeks of pregnancy (do not sell in pregnancy)
-Breastfeeding – aspirin contraindicated

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NSAIDs - interactions

Interactions with other medications:
-Anticoagulant / antiplatelet
-Other NSAIDs
-Ciclosporin
-Diuretics
-ACE inhibitors
-Lithium
-Methotrexate
-SSRIs

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Uses for NSAIDs

Mild to moderate pain:
-Sprians
-Strains
-Headaches
-Dysmenorrhoea
-Toothache
-Colds and flu

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Ibuprofen

Adult oral dose = 200mg -
400mg up to 3 times a day (no more frequently than every 4 hours) -> max dose = 1200mg in 24 hours
-Take with or after food
->Nurofen caplets – not for
use in under 12 years

Naproxen

->Licensed for period pains and menstrual cramps for 15 -> 55 years
->Max three 250mg tablets per day
->Take with / just after meal or snack
->Not to be taken for more than three days in any one cycle

Ibuprofen 100mg/5ml suspension

Indications:
Fever, symptomatic relief of colds and influenza, mild to moderate pain – sore throat,
teething, toothache, headache, minor ache, toothache, headache, minor and sprains
Licensed doses:
3 to 6 months -> >5kg: 2.5ml three times a day for 24
hours only -> avoid in chickenpox

Codeine and dihydrocodeine

->Binds to Mu opioid receptors in the brain and spinal cord (CNS)
->Tolerance and dependence risk!!! – OTC supply limited to 3 days

Aspirin (acetylsalicylic acid)

-For mild to moderate pain in adults and children over 16
-Contraindicated in <16 years – can cause Reye’s syndrome (resulting in serious liver
and brain damage)
-Usual adult oral dose = 300mg – 600mg every 4 to 6 hours -> max dose = 3600mg / 24 hours
-Disclaimer = Aspirin 75mg for cardiovascular risk - not for pain - prolonged effect as an anti-
platelet

Codeine

->Pro-drug - Metabolised by
liver enzymes (CYP2D6) into morphine -> genetic variability in metabolism
->Acute moderate pain (not
anti-pyretic and not anti-
inflammatory)
->Combined with paracetamol, etc, OTC

Dihydrocodeine

->Acts directly on Mu opioid
receptors
->Acute moderate pain (not
anti-pyretic and not anti-
inflammatory)
->Combined with paracetamol, etc, OTC

Codeine/ Dihydrocodeine - side effects

Common side effects = constipation, nausea, drowsiness
->Although can be used in Pregnancy – do not sell OTC = refer to GP
->Contraindicated in breastfeeding
!!!Risk of addiction/ dependence -> max 3 days
Can make headaches worse, if used for > 3 days

Other active ingredients

Caffeine – a weak stimulant that is thought to enhance the analgesic effect and potentially increase absorption
Antihistamines - can act as muscle relaxants and can help with sleep

Dysmenorrhoea - primary

Age: 16-25 Onset of pain: Starts 6-12 months after menarche A few hours before / during menstruation Pathophysiology: No underlying pelvic pathology Excess PG, vasopressin, leukotrienes Symptoms: -Cramp / spasmodic pain in the lower abdomen and suprapubic area - may radiate to the back and inner thigh -Can be associated with nausea, vomiting, headache, fatigue, diarrhoea -Usually self-limiting, lasts for first 1-3 days of menstruation -Periods normal or light -Responds to NSAID, paracetamol, COCP and sometimes heat and TENS

Dysmenorrhoea - secondary

Age: 30-45 Onset of pain: often starts after several years of painless periods, pain not consistently related to menstruation but is exacerbated by it Pathophysiology: Underlying disorder e.g., -Endometriosis -Uterine fibroids -Pelvic inflammatory disease (PID) -Intrauterine device (IUD) insertion Symptoms: -Lower abdominal pain associated with other features related to underlying pathology -Periods often heavy -Treatment based on pathophysiology

Sprain

A torn, stretched or twisted ligament Symptoms: bruising, swelling, inability to move the joint e.g., sprained ankle or knee

Strain

The stretch or tearing of muscles or tendons Symptoms: tenderness and swelling

When to refer / danger symptoms

Treatment: (R)est (I)ce (C)ompression (E)levation Refer: -Fracture or dislocation – inability to weight bear -Severe pain on movement -Persistent pain, even when at rest -Numbness - neuralgia symptoms -Symptoms that have not improved after 48 hours

Osteoarthritis

-Affects knees, hips and small joints of the hand -Loss of cartilage with joint remodelling -Activity related pain -Typically aged >45years -No early morning stiffness (or stiffness lasting no longer than 30 minutes) -Functional impairment- movement limited

Osteoarthritis - pharmacological management

->Paracetamol or topical NSAID = first line ->Consider oral NSAID if simple analgesia ineffective (topical NSAID should then be discontinued) ->Consider weak opioid e.g. codeine when required if NSAID not tolerated or not effective Non-drug measures: weight management and exercise, physio

Back pain

-Most lower back pain is non-specific -Most often seen in those aged 35 to 55 years -Up to 60% of adults have lower back pain at some point in their lives -Common cause of absence from work Risk factors; Non-modifiable: age, genetics Modifiable: fitness, weight, mental health, job related activities, smoking

Back pain - red flags

Red flags from examination -> evidence of neurological deficit (in legs or perineum in the case of low back pain) Red flags from patient history: Possible fracture? -Major trauma / minor trauma in elderly, or osteoporotic Possible tumour / infection? -Age <20 or >50 years old -History of malignancy -Constitutional symptoms (fever, chills, weight loss) -Recent bacterial infection -Intravenous drug use -Immunosuppression -Pain worsening at night, or when supine Possible significant neurological deficit? -Severe or progressive sensory alteration, or weakness -Bladder, or bowel dysfunction

Pharmacological management of lower back pain

1st line - oral NSAIDs e.g. Ibuprofen or naproxen -Consider risk factors -Use lowest effective dose for shortest duration Codeine + Paracetamol ->only consider if NSAID contraindicated, not tolerated or ineffective (for acute back pain only) -> paracetamol alone not recommended (evidence)

Management of LBP

Most effective treatment is to keep moving -> exercise

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