Lecture 17: Minor Ailments & Responding to Symptoms in Community Pharmacy | Pain

Pain

• An unpleasant sensory & emotional experience assciated with, or resembling that associated with, actual or potential tissue damage

Nociception

• When a noxious stimuli activate nociceptors and their pathways

Pain categories

1. Nociceptive - usually associated with acute injury or trauma

2. Neuropathic - arising from nervous system damage or dysfunction

3. Nociplastic - pain is real but not explained by tissue injury or nerve damage

Nociceptive pain

Somatic

• Skin and musculoskeletal

• Injury to skin, muscles, bone, joint and connective tissue

Characteristics

• Pain may be described as dull or aching if in deep tissue, or sharp & pricking under the skin

• Often localised and typically worsens with movement

Visceral

• Injury to internal organs

Characteristics

• Pain tends to be poorly localised and may be cramping or pressure-like

Neuropathic pain

Trauma, injury causing nerve damage or compression (peripheral or central) - changes in nervous system may sustain pain even after an injury heals

Different types of diseases or conditions:

• Neuropathic pain syndromes

• Diabetes

• Shingles

• Post stroke pain

Characteristics

• Often described as unfamiliar feeling using terms like burning, electric shock like sensations, tingling, pins & needles

• May persist long-term

• May be associated with sensitivity of the skin

• Frequently worsens at night possibly due to reduced distractions

Nociplastic pain

Pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage that causes peripheral nociceptors activation or evidence of disease or lesion of the somatosensory system causing pain

Characteristics

• Typically more than 3 months duration

• Pain tends to be poorly localised, often affecting multiple body regions

• Deep, aching or burning

• Persistent and unpredictable

• Sensitive to touch or pressure

• Made worse by stress, fatigue or poor sleep

Pain categorisation - duration

1. Acute (short-term) - less than 3 months, expectation that pain is time limited. Acute pain tends to be a warning to alert the body to prevent further tissue injury

2. Chronic (long-term) - persists beyond expected healing time or more than 3 months

3. Recurrent or Intermittent - comes and goes

Pain categorisation - cause

1. Musculoskeletal - arises from muscles, bones, joints or related soft tissues

2. Inflammatory - triggered by immune response to injury, infection or autoimmune condition

3. Mechanical pain - results from structural distortion or compression of tissues

4. Psychogenic pain - pain primarily influenced by psychological, emotional and behavioural factors

Pharmacological Management (OTC analgesics)

Encourage self-care for acute pain - treat with underlying cause where possible

Non-opioid (PO)

• Paracetamol

• Non-Steriodal Anti-Inflammatory Drugs (NSAIDs) - aspirin, ibuprofen, diclofenac, naproxen

Opioid (PO)

• Codeine

• Dihydrocodeine

Compound analgesics

• Non-opioid & opioid e.g. co-codamol, ibuprofen

Topical preparations

• NSAIDs

• Rubefacients

• Anti-inflammatories for local mouth pain

WHO 3 step analgesic ladder

Adjuvants = antodepressants, anticonvulsants, antispasmodics, muscle relaxant

1. Step 1 - mild pain

• Non-opioid e.g. paracetamol, NSAIDs

2. Step 2 - moderate pain

• Weak opioid e.g. codeine

3. Step 3 - moderate to severe pain

• Strong opioid e.g. morphine

Paracetamol

• Synthetic non-opioid acting in the CNS (CNS COX inhibitor)

• Antipyretic analgesic - no peripheral COX inhibition, no anti-inflammatory activity

• Mild to moderate pain - drug of choice for fever & pain for people with bleeding disorders, peptic ulcers

• Avilable OTC as an oral (GSL, P) or rectal suppository (P) formulation

• Well absorbed orally

• Side effects are few/uncommon

Paracetamol containing products

Paracetamol hepatoxicity

• Hepatic metabolism

• N-acetyl-P-benzoquinoneimine (NAPQI)

• In overdose, more paracetamol is metabolised by  CP450

• NAPQI causes cell death & necrosis

• Potential for live rfailure if untreated

OTC Paracetamol sales

• The law says pharmacies may not sell more than 100 non-effervescent tablets/capsules to a person at one time

• Most OTC pack sizes are 16 or 32 dose units = practically 96 is the maximum number that can be sold

• Use professional judgement to decide the appropriate quantity to supply and what limits to impose

• No legal limits on the quantity of OTC effervescent tablets, powders, granules or liquids 

Non-Steriodal Anti-Inflammatory Drugs (NSAIDs)

• Widely used to reduce pain, inflammation and high temperature

• Antipyretic analgesic (reduces fever) - peripheral COX inhibition, anti-inflammatory activity

• Irreversible COX inhibitor (aspirin)

• Reversible COX inhibitors (ibuprofen, diclofenac, naproxen)

• Hypersensitivity - increased risk in people with asthma, trigger bronchospasm

NSAIDs sales

• Available as OTC

Aspirin

• Oral 300mg GSL (pack of 16)

• Orall 300mg P (pack of 32)

• By law - no more than 100 non-effervescent tablets or capsules can be sold to a person at 1 time

Diclofenac

• Topical gel

• Medicated plaster 140mg GSL

Ibuprofen

• Oral 200mg GSL (pack of 16)

• Oral 400mg (pack of 24, 48, 84)

• Oral suspension 100mg per 5mL  P & GSL

Naproxen

• Oral 250mg P (pack of 9)

OTC Opioids

• Strongest of the alagesics available OTC

• Opioid analgesics bnd opioid receptors (mu, kappa, delta) in the brain, spinal cord and gastrointestinal tract

• Antitussive - supresses coughs e.g. codeine

• Antidiarrhoeal - acts on Mu receptors in gut, doesn’t cross BBB so not an analgesic e.g. loperamide

OTC Opioids analgesic

• Codeine & dihydrocodeine available as compund oral formulations (P)

  • Combined with paracetamol

• Only indication is short-term treatment of acute moderate pain not relieved by paracetamol or aspirin or ibuprofen alone

Codeine

• Pro-drug of morphine

• Some direct action

• Morphine main analgesic effect

• Hepatic CYP2D6

• Drug-drug interactions

OTC Opioids: codeine & dihydrocodeine

Side effects:

• Euphoria (less anxiety)

• Sedation

• Reduced gut motility (constipation)

• Respiratory depression

• Nausea & vomiting

• Confusion (especially in elderly)

OTC Consultation questioning about Pain

OTC management of acute pain

• Bleeding

• Seizure, dizziness, impaired consciousness, numbness

• Visual disturbance

• Fever

• Gradual onset

• Neck pain or stiffness with photophobia

• Progressive or persistent headache

• Sudden onset severe headache

• Weight loss

Common presenting complaints

Common presenting complaints

Topical Formulations

NSAID creams and gels

• As effective as oral NSAIDs for musculoskeletal pain

Rubefacients - also known as counter-irritants

• Cause vasodilation

• Rare adverse effects