ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Non-Steroidal Anti-Inflammatory Drug (NSAID) Pregnancy: Avoid (3rd trimester absolute — premature closure of ductus arteriosus); caution if essential in 1st/2nd trimester

Diclofenac

Brand names: Voltarol, Arthrotec (with misoprostol)

Adult dose

Dose: Oral: 75–100 mg/day in 2–3 divided doses (or 75 mg SR BD). Topical gel (Voltarol): apply 2–4 g QDS. IM: 75 mg OD (max 150 mg/day).
Route: Oral, topical, or IM
Frequency: BD–TDS oral; QDS topical
Max: 150 mg/day oral
Significant CV risk (dose-dependent — higher than other NSAIDs per MHRA 2013 review). Avoid in ischaemic heart disease, stroke, peripheral arterial disease. Always prescribe at lowest effective dose for shortest duration.

Paediatric dose

Dose: 0.5 mg/kg
Route: Oral or IM
Frequency: BD–TDS
Max: 3 mg/kg/day (max 150 mg/day)
Concentration: 25 mg/5 mL syrup mg/ml
Children ≥6 months for juvenile arthritis: 0.5–1 mg/kg BD–TDS. IM not recommended in children <1 year.

Dose adjustments

Renal

Avoid in renal impairment (eGFR <30 — can precipitate AKI)

Hepatic

Caution in hepatic impairment — hepatotoxicity possible

Paediatric weight-based calculator

Children ≥6 months for juvenile arthritis: 0.5–1 mg/kg BD–TDS. IM not recommended in children <1 year.

Clinical pearls

  • MHRA 2013: diclofenac has higher CV risk than other NSAIDs (except coxibs) — prescribe with caution; avoid in CV disease
  • All oral NSAIDs require PPI gastroprotection if age >45, on steroids/anticoagulants, or previous GI disease
  • Topical diclofenac (Voltarol gel): much lower systemic absorption — preferred for localised musculoskeletal pain
  • 'Triple whammy' — NSAID + ACEi/ARB + diuretic: high AKI risk especially in elderly, ill, or dehydrated patients

Contraindications

  • Ischaemic heart disease (oral/parenteral)
  • Peripheral arterial disease
  • Cerebrovascular disease
  • Moderate-severe HF
  • Previous GI ulcer/bleed
  • Severe renal/hepatic impairment
  • 3rd trimester pregnancy

Side effects

  • GI ulceration and bleeding
  • Cardiovascular events (MI, stroke — dose-dependent)
  • Renal impairment
  • Hypertension
  • Fluid retention
  • Hepatotoxicity (rare but can be severe)
  • Hypersensitivity (bronchospasm in aspirin-sensitive asthma)

Interactions

  • Anticoagulants — increased bleeding risk
  • Aspirin — reduced aspirin antiplatelet effect + GI risk
  • Lithium — increased lithium levels
  • Methotrexate — reduced methotrexate clearance (toxicity risk)
  • ACEi/ARBs — reduced antihypertensive effect + AKI risk

Monitoring

  • Renal function (before starting in at-risk patients)
  • Blood pressure
  • GI symptoms
  • Signs of oedema
  • Hepatic function (prolonged use)

Reference: BNFc; BNF; MHRA Drug Safety Update 2013; NICE NG193. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways