Nsaids

5 min read Last updated April 8, 2026

What NSAIDs do (core concepts)

  • NSAIDs reduce pain, inflammation, and fever by inhibiting cyclo-oxygenase (COX) enzymes and therefore prostaglandin production.
  • Analgesic effect is opioid-sparing (often reduces opioid requirement and opioid side-effects).
  • COX-1 is involved in gastric protection, platelet function, and renal blood flow; COX-2 is more inducible in inflammation (COX-2 selective drugs tend to cause less gastric irritation but still have renal and cardiovascular risks).
  • They are best used as part of multimodal analgesia (e.g., paracetamol + NSAID ± regional anaesthesia ± opioid as needed).

Common peri-operative NSAIDs in the UK (examples)

  • Ibuprofen: common oral NSAID for ward/discharge; check asthma/renal/GI risk.
  • Diclofenac: oral/PR; useful but higher cardiovascular risk signal than some alternatives; avoid in established ischaemic heart disease/heart failure.
  • Naproxen: longer acting; often considered lower cardiovascular risk than diclofenac (still GI/renal risks).
  • Ketorolac: potent; often used short-term; higher risk of renal impairment and bleeding—use carefully and avoid in high-risk patients.
  • COX-2 selective (e.g., celecoxib/etoricoxib): less platelet effect and less GI ulceration than non-selective NSAIDs, but renal effects still occur; consider cardiovascular risk.

When to consider an NSAID (typical “first time” scenarios)

  • Post-op pain where inflammation contributes (orthopaedics, dental, soft tissue surgery) and there are no major contraindications.
  • When you want opioid-sparing in patients prone to nausea, ileus, sedation, or respiratory depression (but still check renal/GI/bleeding risk).
  • Day-case pathways: a single peri-operative dose can improve comfort and reduce opioid need at home (ensure clear discharge advice).
  • Renal colic: NSAIDs can be very effective (reduce ureteric spasm/inflammation) but avoid if AKI/dehydrated/sepsis.

Pre-op checklist before prescribing/administering

  • Kidneys/volume status: recent creatinine/eGFR if available; avoid if AKI, significant CKD, dehydration, sepsis, or hypotension.
  • GI risk: history of peptic ulcer/upper GI bleed; consider PPI cover if NSAID essential and risk is moderate (follow local policy).
  • Bleeding risk: active bleeding, high-risk surgery for bleeding, thrombocytopenia, coagulopathy; remember non-selective NSAIDs inhibit platelet function (COX-2 selective have minimal platelet effect).
  • Asthma/NSAID sensitivity: ask about previous wheeze, facial swelling, or anaphylaxis after aspirin/ibuprofen/naproxen (avoid if suspected NSAID-exacerbated respiratory disease).
  • Cardiovascular disease: avoid diclofenac in IHD, cerebrovascular disease, peripheral arterial disease, or heart failure; use lowest effective dose for shortest time.
  • Pregnancy: avoid in 3rd trimester (risk of premature ductus arteriosus closure and oligohydramnios); seek senior/obstetric advice if unsure.
  • Drug interactions: ACE inhibitor/ARB + diuretic + NSAID (“triple whammy”) increases AKI risk; anticoagulants/antiplatelets increase bleeding risk; lithium and methotrexate toxicity can be increased.

Dosing principles (safe practice)

  • Use the lowest effective dose for the shortest time; reassess daily in inpatients.
  • Avoid stacking multiple NSAIDs (e.g., ibuprofen plus diclofenac) — no added benefit, increased harm.
  • If giving peri-operatively, document timing and agent clearly to avoid duplicate dosing on the ward.
  • Consider gastroprotection (e.g., PPI) for higher GI-risk patients if NSAID is needed and not contraindicated (follow local guidance).

Adverse effects to recognise early

  • Renal: reduced renal perfusion → AKI, fluid retention; higher risk with dehydration, sepsis, CKD, ACEi/ARB, diuretics, elderly.
  • GI: dyspepsia, gastritis, ulceration, GI bleeding (may be occult).
  • Bleeding: platelet inhibition (non-selective NSAIDs) can increase surgical bleeding; risk depends on procedure and patient factors.
  • Respiratory/allergy: bronchospasm in susceptible asthma; urticaria/angioedema; anaphylaxis (rare).
  • Cardiovascular: fluid retention, hypertension, worsening heart failure; thrombotic risk varies by agent and dose.

Practical peri-operative tips

  • If hypotensive, septic, bleeding, or clearly volume-depleted: avoid NSAIDs and choose alternatives (paracetamol, regional techniques, opioids carefully).
  • After major surgery with high AKI risk (e.g., major abdominal, vascular): be cautious—discuss with senior and consider delaying until stable and euvolaemic.
  • If neuraxial/regional anaesthesia: NSAIDs alone are not usually a contraindication, but consider overall bleeding risk and other anticoagulants; follow local/regional guidelines.
  • On discharge: advise to avoid additional over-the-counter NSAIDs and to stop and seek help if black stools, vomiting blood, severe abdominal pain, wheeze, facial swelling, or reduced urine output.
What is the main mechanism of NSAIDs?

– Inhibit COX enzymes → reduce prostaglandins – Leads to analgesic, anti-inflammatory, and antipyretic effects

Why can NSAIDs cause AKI?

– Prostaglandins help maintain renal blood flow (especially when kidneys are “stressed”) – NSAIDs remove this support → reduced renal perfusion, particularly in dehydration, sepsis, CKD, ACEi/ARB + diuretic use

Which patients should I avoid NSAIDs in (common peri-op list)?

– AKI or significant CKD – Hypovolaemia/dehydration, sepsis, ongoing hypotension – Active GI ulcer/bleed or very high GI bleed risk – Known NSAID/aspirin allergy or NSAID-triggered asthma – Severe heart failure; avoid diclofenac in established atherosclerotic disease

Do NSAIDs increase bleeding?

– Non-selective NSAIDs inhibit platelet function (reversible) – Clinically relevant bleeding risk depends on surgery type and patient factors – COX-2 selective agents have minimal platelet effect but still carry renal/CV risks

Can I give an NSAID with LMWH or DOACs?

– Caution: combined therapy increases bleeding risk – If analgesic benefit is important, discuss with senior and consider COX-2 selective options and gastroprotection (as appropriate) – Avoid if bleeding risk is high

What is the ‘triple whammy’?

– ACE inhibitor/ARB + diuretic + NSAID – Markedly increases AKI risk, especially with dehydration or intercurrent illness

When are NSAIDs particularly helpful?

– Inflammatory pain (e.g., orthopaedics, dental, soft tissue) – Opioid-sparing in patients prone to nausea/sedation – Renal colic (if kidneys and volume status are OK)

If a patient has asthma, can they have ibuprofen?

– Many asthmatics tolerate NSAIDs – Avoid if history suggests NSAID-exacerbated respiratory disease (wheeze/nasal symptoms after aspirin/NSAID) – If unsure or severe asthma: discuss with senior and consider alternatives

What should I monitor after starting an NSAID in hospital?

– Urine output and fluid balance – Creatinine/eGFR if ongoing use or high-risk patient – Signs of GI bleeding (melaena, haematemesis, unexplained anaemia) – Blood pressure/heart failure symptoms in susceptible patients

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