Minor Ailments - OTC analgesics (Pain killers) Flashcards
What is pain?
- An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
- A personal experince nfluenced by biological, psychological, & social factors
- A person’s report of an experince as pain should be respected
*
Nociception & pain
- Pain & nociception are different - Pain cannot be
inferred solely from activity in sensory neurons
What is Nociception?
- When a noxious stimuli (e.g., tissue injury or temperature
extremes) activate nociceptors (pain receptors, sensory neurons with specialised nerve endings widely distributed in skin, tissues, muscles, joints, visceral organs) & their pathways - Nociception is like the body’s alarm system, detecting potential harm
- Pain is the feeling we experience in response to that alarm.
Classification of Pain BY TYPE
- Nociceptive – arising from pain receptors (e.g., twisted ankle)
- Neuropathic (nerve pain/neuralgia) – arising from nervous system (e.g.,trigeminal neuralgia, shingles)
- Pain with no apparent cause
Pain is…
Classification of Pain BY DURATION
- Acute (short-term) – hours to days, expectation that pain is time limited (e.g., twisted ankle, tooth extraction, post operative pain)
- Persistent or Chronic (long-term) – months to years (e.g., arthritis)
- Recurrent or Intermittent – comes and goes (e.g., back pain)
Classification of Pain BY CONDITIONS
- headache
- arthritis
- musculoskeletal injury
What is Nociceptive Pain?
- Arising from activation of pain receptors (nociceptors)
- 2 types Somatic & Visceral
Somatic nociceptive pain
- In the skin & musculoskeletal
- Injury to skin, muscles, bone, joint and connective tissue
- Pain may be described as dull or aching if in deep tissue, or sharp & pricking if under the skin
*
Visceral nociceptive pain
- Injury to internal organs (e.g., intestine or gall bladder)
- Pain tends to be poorly localised & may be cramping
- More dispersed
What is Neuropathic Pain?
- Arising from damage or disturbance of function of a nerve
- often described as unfamiliar pain, which may be burning or like electricity
- may be associated with sensitivity of the skin
- Can’t be managed using OTC meds
- Needs to be referred
Neuropathic Pain may be associated with
Trauma:
may follow nerve damage or compression
* usually, the injury that starts the pain involves the peripheral nerves or the central nervous system
* changes in nervous system that sustain pain even after an injury heals
* Trauma heals but pain may still continue
**Diff types of disease or conditions **:
* Neuropathic pain syndromes
* Diabetes (diabetic neuropathy)
* Shingles (postherpetic neuralgia)
* Trigeminal neuralgia
* Post-stroke pain
* Complex regional pain syndromes = reflex sympathetic dystrophy (RSD) = causalgia)
Pharmacological Management (OTC analgesics)
Non-opioid:
* Paracetamol
* NSAIDS = Aspirin , ibuprofen , Diclofenac, naproxen
Opiod
* Codeine
* Dihydrocodeine
Compound analgesics:
* Non-opioid & opioid (e.g., co-codamol, co-
dydramol)
* Non-opioid & Non-opioid (e.g., ibuprofen/paracetamol 200/500)
Topical preparations
* NSAIDs
* Rubefacients ( increase blood flow to the area)
* Anti-inflammatories for local mouth pain (e.g., benzydamine)
Paracetamol containing products
- Solpadine Plus = codeine + caffeine + paracetamol
- Solpadeine Max = paracetamol + codeine 8 mg per tab
- Solpadeine Max Soluble = paracetamol + codeine + caffeine
- Solpadeine headache = caffeine + paracetamol
- Syndol = sedative antihistamine + codeine, caffeine + paracetamol
- Feminax period pain = codeine + paracetamol
- Paramol = dihydrocodeine + paracetamol
- Migraleve pink = paracetamol + sedative antihistamine + codeine
- Migraleve yellow = codeine + paracetamol
- Panadol night pain = paracetamol + sedative antihistamine
- Panadol ultra = codeine + paracetamol
- Nurmol = Ibuprofen + paracetamol
- Caffine = stimulant = 100mg + caffine + standard dose of common analgesic gives a small but significant improvement to analgesic effect
WHO three-step analgesic ladder for pain management
- Developed for cancer pain
- Adjuvants = antidepressants, anticonvulsants, antispasmodics, muscle relaxant, bisphosphonate or corticosteroid)
- Used OTC
1. STEP 1= Mild pain = non-opiod (e.g.,paracetamol, NSAID)(± adjuvant)
Step up if persisits or increases
2. STEP 2 = Moderate pain = Weak opioid
(e.g., codeine) ± non-opioid (± adjuvant)
Step up if persisits or increases
3. STEP 3= Moderate to severe pain = Strong opioid (e.g., morphine) ± non-opioid (± adjuvant)
What is Paracetamol?
- Synthetic non-opioid = acts in CNS (CNS COX inhibitor)
- Antipyretic analgesic=decrease fever+body temp
- no peripheral COX inhibition
- Dosen’t reduce inflammation
- Increases prostaglandins production
- Prostaglandins = lower threshold for pain
- paracetamol stops this
Paracetamol
- Mild to moderate pain
- Drug of choice for fever & pain for people with bleeding disorders, peptic ulcers
- Available OTC as an oral (GSL, P) or rectal suppository (P) formulation
- Well absorbed orally:
- Peak plasma concentrations in 30-60 minutes
- Plasma half-life 2-4 hours
- Side effects few, uncommon
- oral adult does = 500 -1000mg every 4-6 hrs (max 4g in 24 hrs)
- Oral paediatric dose by age (suspension)
Paracetamol Hepatotoxicity (1)
- Paracetamol is metabolised in the liver via glucuronidation & sulfation pathway.
- 0ver 80% of paracetamol goes through these 2 pathways
- A tiny amount goes through an enzyme= cytochrome P450 in the liver & produces a highly toxic metabolite (NAPQI)
- Mopped up in cells by glutathione
- Taking too much paracetamol saturates the 2 pathways so more paracetamol gets pushed through cytochrome p450 = More NAPQI
- NAPQI causes cell death & necrosis
- Potential for liver failure if untreated
- Treatment IV acetylcysteine
OTC Paracetamol Sales
- law= pharmacies may not sell more than 100 non-effervescent tablets/capsules to a person at any one time
- Most OTC pack sizes are 16 or 32 dose units
- 96 = max number that can be sold
- No legal limits on the quantity of OTC effervescent tablets, powders, granules or liquids
- MHRA= no more than two packs should be supplied at any one time
Paracetamol Hepatotoxicity (2)
- Normal therapeutic doses can affect those w/ low glutathione stores = Old age, malnutrition, fasting/anorexia, or use of enzyme inducing drugs can cause more damage,chronic alcohol abuse or w/ glutathione synthesis deficiency.
- Chronic use of alcohol or s/ meds = increase activity of CYP450 = increase NAPQI
- US FDA = limits prescription combination products to 325 mg paracetamol
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
- NSAIDs available OTC
Aspirin: - 75mg = for blood thinning = GSL & P med
- 300-900mg every 4-6 hrs= for pain
- Oral 300 mg GSL (Pack size 16)
- Oral 300 mg P (Pack size 32)
- By law - no more than 100 non-effervescent tablets or capsules can be sold to a person at any one time
Diclofenac: - Topical gel 2.32% P/GSL & 1.16% GSL
- Medicated plaster 140 mg (up to 7 days ) = GSL
ibuprofen: - Oral 200mg GSL (Pack size 16)
- Oral 400mg P (Pack size 24, 48, 84)
- Oral suspension 100 mg per 5 mL P & GSL
- Topical gel 5% & 10% P & GSL
Naproxen: - Oral 250 mg P (Pack size 9) for dysmenorrhoea
(period pain & cramps) - Can only be sold OTC for period pain
Types of NSAID’s
- Irreversible COX inhibitor (aspirin)
- Reversible COX inhibitors (e.g., ibuprofen, diclofenac, naproxen)
NSAID’s
- Used to decrease pain, inflammation & high temp
- Antipyretic analgesic = decreases fever
- Act on peripheral COX inhibition = anti-inflammatory activity
NSAID’s side effects (1)
- Inhibition of Peripheral COX causes side effects
1. Gastrointestinal: - Prostaglandins affects how thick the lining of our stomach is
- reduces cytoprotective gastrointestinal prostaglandins
- increases risk of gastritis, peptic ulcers, bleeding
2. Renal: - Reduces blood flow through the kidneys
- reduce prostaglandins = dilate the renal artery= decrease renal lood flow activates Renin Angiotensin-Aldosterone System to retain sodium and water= increase bp
3. Cardiovascular: - decrease prostaglandin = * Tip the clotting cascade towards clotting = increases risk of thrombotic event
- Lowest with ibuprofen & naproxen so oral diclofenac is not sold OTC
NSAID’s side effects (2)
Hypersensitivity:
* increased risk in people w/ asthma = s/ are intolerant
* trigger bronchospasm
Specific issues with aspirin (acetylsalicylic acid)
* Linked with Reye’s syndrome = rare condition causing liver and brain damage= Not for children & babies
* Aspirin overdose can be fatal (salicylism – tinnitus, vertigo, deafness, nausea, vomiting & eventually seizures or coma)
OTC Opioids
- Strongest pain med available OTC
- Opioid analgesics bind opioid receptors (mu, kappa, delta) in the brain, spinal cord & GI tract
- S/ are not pain meds = antitussive, supress coughing e.g codeine, dextromethorphan - no analgesic action
- Antidiarrhoeal (loperamide, acts on Mu receptors in gut, doesn’t cross blood brain barrier so not an analgesic)= slows gut motility
OTC Opioid analgesics
- Codeine & dihydrocodeine available as compound oral formulations = P:
- combined with paracetamol
- codeine (co-codamol 8/500)
- dihydrocodeine (co-dydramol)
- used for = short-term treatment of acute
moderate pain not relieved by paracetamol or aspirin or ibuprofen alone - Only for children 12+ years & adults
- Pack sizes 32+ = POM ( includes effervescent tablets)
- cna causse addiction = 3 day use ONLY
CYP2D6 polymorphisms
- Converts codeine into morphine
- Side effects = respiratory depression ( hypoventillation = breathe too slowly) + Sedation ( drowsiness)
- Poor metabolisers (5-10% of people) – unable to convert – little analgesic benefit but still get side effects
- Intermediate metabolisers (2-11% of people) – little analgesic benefit but still get side effects
- Extensive metabolisers (77-92% of people) – ~10% conversion to morphine = analgesic benefit
-
Ultra-rapid metabolisers (1-2% of people) – efficient conversion can lead to morphine toxicity. Life-threatening
opioid toxicity reported in adults receiving low dose of codeine (75 mg per day) = why codeine isn’t given to children
OTC Opioids: Codeine
- Codeine = pro drug = has v/ minimal anagelsic activity on its own
- Metabolised by cytochrome P450 into morphine = the active drug
- If you have polymorphism in your cytochrome P450 you will not really fell the effects of codeine but you will get the side effects.
OTC Opioids: Codeine & Dihydrocodeine side effects
- Euphoria ( decrease anxiety) = Addictive
- Sedation
- Decrease Gut motility (constipation)
- Respiratory depression
- Nausea & vomiting
- Confusion (especially in elderly)
OTC Opioids: Dihydrocodeine
- Dihydrocodeine (+ metabolites) has
analgesic action - Elevate the pain threshold
- Alter reaction to pain
Why oral formulations?
- Soluble, quicker acting & particularly if nausea present
- Maximum dosing of paracetamol:
- ± NSAID (with all cautions & warnings of side effects)
- ± codeine (warn constipation & drowsiness)
- ± antiemetic (for migraine with nausea/vomiting only)
- Small dose of codeine may have only a small additional analgesic effect but
cause additional side-effects (e.g., counsel re. constipation) - Caffeine containing preparations may have a small additional analgesic effect ( 100 mg)
OTC Consultation Questioning about Pain
OTC Management of Acute Pain
- Explore symptoms
Red flags for referral: - Bleeding
- Seizure, dizziness, impaired consciousness, numbness
- Visual disturbance
- Fever (potential infection)
- Gradual onset (chronic condition e.g. osteoarthritis)
- Neck pain or stiffness with photophobia (meningitis)
- Progressive or persistent headache
- Sudden onset severe headache
- Weight loss
- 1st-line treatment depends on presenting complaint, intercations & preferences
Common Presenting Complaints (2)
Lower back pain:
* 60-80% of people will experience at some stage & 20% of population will consult GP
* Staying active beneficial – exercise/movement
* NSAIDs are first-line at lowest dose compatible with any comorbidities. NICE guideline NG59 2016 (revised 2020)
**Activity-related soft tissue injuries/ sports injuries **:
Common Presenting Complaints ( 1)
Headache(usually self-limiting):
Primary
* Tension headache
* Migraine
* Cluster headache
Secondary (caused by
infection, neoplasm, trauma etc)
* Sinus pain (sinusitis)
* Temporal arteritis
Dysmenorrhoea = (menstrual/period pain)
* Cramps in muscular wall of womb → compression of blood vessels → reduced
oxygen → release of prostaglandins → pain
* Cramping, spreading to back & sometimes to thighs
* Ibuprofen or naproxen (only OTC indication is period pain)
Mouth Pain ( toothache)
* Systemic therapy - use max. paracetamol, be careful with NSAIDs as people tend to
reduce their diet and over-do analgesics for toothache
* Refer to dentist - Antibiotics may be required for infection
- Temporary relief possible from topical preparations (e.g. local anaesthetic gels & benzydamine – numbness & inflammation)
Topical Formulations
- Do not use the 2 together
- NSAID (ibuprofen, diclofenac) creams & gels:
- As effective as oral NSAIDs for musculoskeletal pain (Clinical trial data)
- Some systemic absorption
- caution with people with hypersensitivity
- reduced risk of systemic side effects
- Drug appears to concentrate in the affected tissues (where applied)
Rubefacients (methyl salicylates, menthol, capsaicin): - Also known as counter-irritants
- Cause vasodilation – sensation of warmth- mild skin irritation = distracts from pain
- Rare adverse effects
- not enough evidence to support use of methyl salicylate rubefacients for chronic or acute pain
Tension headache
symptoms*
* Mild to moderate pain
* Tight band around head
* dull ache
* constant pressure
Causes
* Lack of sleep
* stress
* alcohol
* dehydration
treatment:
* Paracetamol
* aspirin
* ibuprofen
cluster headache
sytmptoms:
* Severe unilateral pain above and within eye and temporal origin.
* multiple headaches one after the other.
causes:
* associations with lacrimation and rhinitis.
* lack of sleep
* dehydration
* alcohol.
treatments
* NSAIDS
* Paracetamol
* opioids
migrane
symptoms:
* Unilateral pulsing or throbbing.
* Nausea
* vomiting
* light sensitivity
**causes **:
some triggers:
* Sleep disruption
* dehydration
* hormone fluctuations
**tratment **:
- NSAID’s
- paractetamol
Medication overuse headache
symtoms:
* Dull, tension-type headaches.
causes:
* overuse of OTC pain relievers( more than 15 days in a month) i.e ibuprofen.
