Analgesia - mild-to-moderate pain
Exam Tips
- In OSCE prescribing stations, state: treat cause first, start with safest option, lowest effective dose, shortest duration, and review.
- Memorise core paracetamol adult dose (500 mg-1 g every 4-6 hours; max 4 g/day) and child age-banded dosing with max four doses/day.
- For children: use paracetamol or ibuprofen alone first; if inadequate, switch; only then consider alternating with careful timing and written instructions.
- Name high-yield contraindications: aspirin under 16 years, NSAID GI/renal/CV risks, and opioid dependence/overdose risks.
- Always mention safety-netting: red flags, overdose advice, and avoidance of duplicate OTC products.
Definition
Analgesia for mild-to-moderate pain is a stepwise pharmacological approach used to reduce pain intensity and improve function while treating the underlying cause where possible. In UK practice, first-line options are usually paracetamol or an NSAID, with short-course weak opioids considered only when safer options are inadequate and after individual risk assessment.
Pathophysiology
Pain is a biopsychosocial experience rather than a pure nociceptive signal, so severity and treatment response vary between patients with the same tissue injury. Nociceptive and inflammatory pain are commonly mediated by prostaglandins generated via cyclo-oxygenase (COX) pathways: non-selective NSAIDs inhibit COX-1 and COX-2, while coxibs are relatively COX-2 selective. COX-1 inhibition explains much of NSAID gastrointestinal and renal toxicity; COX-2 inhibition contributes to analgesic and anti-inflammatory effect. Aspirin irreversibly inhibits COX and platelet thromboxane synthesis, so it is mainly antithrombotic at low dose rather than preferred analgesia. Paracetamol acts predominantly centrally (likely COX-related CNS effects) with analgesic/antipyretic but minimal anti-inflammatory effect. Weak opioids (for example codeine, dihydrocodeine, meptazinol) reduce pain perception through opioid receptors, and tramadol additionally inhibits serotonin/noradrenaline reuptake. See pain-mechanism diagrams in standard pharmacology texts (for example COX pathway and descending inhibitory pathways figures).
Risk Factors
- Older age (higher risk of NSAID GI bleed, renal injury, and opioid adverse effects)
- History of peptic ulcer disease or GI bleeding
- Chronic kidney disease, dehydration, heart failure, or concomitant nephrotoxic drugs
- Cardiovascular disease or high CV risk (relevant to some NSAIDs/coxibs)
- Liver disease, alcohol dependence, malnutrition, low body weight (<50 kg), or prolonged paracetamol use
- Polypharmacy (for example anticoagulants, antiplatelets, SSRIs, corticosteroids, ACE inhibitors/diuretics)
- Past substance misuse or mental health comorbidity increasing opioid dependence risk
- Children under 16 years for aspirin and most opioid use in primary care
Clinical Features
Symptoms
- Pain score increase with reduced sleep, mood, and functional ability
- Pain quality suggesting mechanism: throbbing/aching (nociceptive), inflammatory tenderness/stiffness, burning/shooting (neuropathic), widespread disproportionate pain (nociplastic)
- Breakthrough pain despite over-the-counter analgesics
- Adverse-effect symptoms from analgesics (dyspepsia, nausea, constipation, drowsiness)
Signs
- Localized tenderness, reduced range of movement, or pain-limited function
- Inflammatory signs depending on cause (warmth, swelling, erythema)
- Medication toxicity signs (for example dehydration, hypotension, confusion, rash, jaundice in severe hepatotoxicity)
- Red flags for serious pathology (fever/sepsis signs, focal neurology, peritonism, cardiorespiratory compromise)
Investigations
Management
Lifestyle Modifications
- Treat the underlying cause of pain and use non-drug measures (restoration of function, pacing, ice/heat where appropriate, sleep optimisation)
- Set realistic goals (pain reduction plus functional improvement, not complete pain elimination)
- Use the lowest effective dose for the shortest duration and review response early
- Educate about avoiding duplicate over-the-counter products containing paracetamol or NSAIDs
- For children using alternating paracetamol/ibuprofen, provide written timing advice or a dosing diary
Pharmacological Treatment
Paracetamol (first-line in many patients)
- Adults: paracetamol 500 mg to 1 g orally every 4-6 hours, max 4 g/24 h
- Children (oral, every 4-6 hours, max 4 doses/24 h): 3-5 months 60 mg; 6-23 months 120 mg; 2-3 years 180 mg; 4-5 years 240 mg; 6-7 years 240-250 mg; 8-9 years 360-375 mg; 10-11 years 480-500 mg; 12-15 years 480-750 mg; 16-17 years 500 mg-1 g
- Rectal option if needed: 3-11 months 60-125 mg; 1-4 years 125-250 mg; 5-11 years 250-500 mg; 12-17 years 500 mg
Generally well tolerated but use caution (and consider dose reduction) in severe liver disease, severe renal impairment, chronic alcohol use, malnutrition, dehydration, or body weight <50 kg. Serious overdose risk: urgent NPIS/TOXBASE-guided management. Warn about duplicate combination products.
Non-steroidal anti-inflammatory drugs (NSAIDs) and coxibs
- Ibuprofen: adults typically 200-400 mg three times daily (max usually 2.4 g/day prescribed)
- Naproxen: adults typically 250-500 mg twice daily
- Diclofenac: adults typically 50 mg two to three times daily (max 150 mg/day)
- Celecoxib: commonly 100-200 mg once or twice daily (max usually 400 mg/day)
- Etoricoxib: commonly 30-60 mg once daily (indication-dependent)
Choose by GI/CV/renal risk profile; co-prescribe gastroprotection (for example PPI) when GI risk is elevated. Avoid or use extreme caution in active GI ulcer/bleeding, severe renal impairment, decompensated heart failure, uncontrolled hypertension, and late pregnancy. In children, first-line NSAID is ibuprofen; aspirin is contraindicated under 16 years (Reye syndrome risk), and naproxen/diclofenac use is indication- and age-restricted.
Weak opioids (short-course rescue when first-line inadequate)
- Codeine phosphate: 30-60 mg every 4-6 hours (max 240 mg/day)
- Dihydrocodeine: 30 mg every 4-6 hours (max 240 mg/day)
- Tramadol: 50-100 mg every 4-6 hours (max 400 mg/day)
Reserve for limited duration due to dependence, sedation, falls, constipation, and overdose risk; review frequently and deprescribe promptly. Avoid codeine in breastfeeding and in known CYP2D6 ultra-rapid metabolisers; avoid tramadol with MAOIs and use caution with SSRIs/SNRIs due to serotonin syndrome/seizure risk. In UK primary care, opioids are generally not recommended for mild-to-moderate pain in children under 16 without specialist advice; codeine/dihydrocodeine/tramadol are not licensed under 12 years.
Fixed-dose combinations
- Paracetamol + codeine
- Paracetamol + dihydrocodeine
- Paracetamol + tramadol
- Aspirin + codeine
Can simplify dosing but increase risk of inadvertent overdose (especially paracetamol duplication) and long-term opioid exposure; use clear stop dates and counsel carefully.
Complications
- Inadequate pain control leading to impaired mobility, poor sleep, and delayed recovery
- Medication-overuse and accidental duplicate dosing (especially paracetamol combinations)
- Paracetamol hepatotoxicity in overdose or high-risk states
- NSAID-related GI ulceration/bleeding, acute kidney injury, fluid retention, and cardiovascular events
- Opioid-related dependence, constipation, sedation, falls, respiratory depression, and withdrawal
- Rare severe hypersensitivity reactions (including anaphylaxis and serious skin reactions)
Prognosis
Most acute mild-to-moderate pain improves as the underlying condition resolves, especially with early cause-directed management and time-limited analgesia. Prognosis worsens when pain persists beyond expected healing, when adverse drug effects occur, or when opioids are continued without clear benefit and review.
Sources & References
✅NICE Guidelines(1)
- Analgesia - mild-to-moderate pain[overview]