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NSAID (rapid-onset salt)

Diclofenac potassium

Brand names: Voltarol Rapid, Voltfast

Diclofenac potassium is the rapidly-absorbed salt of the non-steroidal anti-inflammatory drug (NSAID) diclofenac, used for short-term relief of pain and inflammation including acute musculoskeletal conditions, dysmenorrhoea and migraine.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Pain or primary dysmenorrhoea: 50 mg three times a day. Osteoarthritis: 100 to 150 mg/day in divided doses — 50 mg twice a day or three times a day. Rheumatoid arthritis: 150 to 200 mg/day in divided doses — 50 mg three times a day or four times a day.
Route: Oral — diclofenac potassium immediate-release tablets
Frequency: Three times a day for pain or primary dysmenorrhoea; twice or three times a day for osteoarthritis; three or four times a day for rheumatoid arthritis
SCOPE: this covers the page's primary route (oral) and its rheumatology indications (osteoarthritis and rheumatoid arthritis), plus pain and primary dysmenorrhoea. It is IMMEDIATE-RELEASE TABLET labelling only — the fetched label says nothing about the oral powder/sachet formulation named in the page's brand list, and nothing about migraine. || VERBATIM SOURCE WORDING (US label, DOSAGE AND ADMINISTRATION): 'Carefully consider the potential benefits and risks of diclofenac potassium immediate-release tablets and other treatment options before deciding to use diclofenac potassium tablets. Use the lowest effective dose for the shortest duration consistent with individual patient treatment goals... After observing the response to initial therapy with diclofenac potassium tablets, the dose and frequency should be adjusted to suit an individual patient's needs. For treatment of pain or primary dysmenorrhea the recommended dosage is 50 mg three times a day. With experience, physicians may find that in some patients an initial dose of 100 mg of diclofenac potassium tablets, followed by 50-mg doses, will provide better relief. For the relief of osteoarthritis the recommended dosage is 100 to 150 mg/day in divided doses, 50 mg twice a day or three times a day. For the relief of rheumatoid arthritis the recommended dosage is 150 to 200 mg/day in divided doses, 50 mg three times a day or four times a day.' || LOADING DOSE OPTION (verbatim, as above): 'an initial dose of 100 mg of diclofenac potassium tablets, followed by 50-mg doses' may give better relief in some patients with pain or primary dysmenorrhoea. || FORMULATION WARNING (verbatim): 'Different formulations of diclofenac [VOLTAREN (diclofenac sodium enteric-coated tablets); Voltaren-XR (diclofenac sodium extended-release tablets); diclofenac potassium tablets] are not necessarily bioequivalent even if the milligram strength is the same.' Do not substitute milligram-for-milligram between diclofenac salts or release profiles. || MAXDOSE deliberately left empty: the fetched label states no maximum daily dose for diclofenac potassium in any wording. The highest figure it prints is the top of the rheumatoid-arthritis recommended range (200 mg/day), which is a recommended range boundary and not a stated ceiling, so it has not been published as one. Re-source the UK SPC §4.2 if a maximum is required. || PAEDIATRIC: paedDose is null — the fetched label contains no paediatric dosing for diclofenac potassium. For any under-18 dose, verify against a children's formulary.

Dose adjustments

Renal

Not stated — no renal-impairment dosing statement was retrieved. This bundle holds only the US label's DOSAGE AND ADMINISTRATION, CONTRAINDICATIONS and (truncated) ADVERSE REACTIONS sections; its WARNINGS section, which the label cross-references for 'Renal Toxicity and Hyperkalemia', was not fetched, and there is no UK SPC in this bundle. Verify against the manufacturer SPC (eMC) before use in renal impairment.

Hepatic

Not stated — no hepatic-impairment dosing statement was retrieved. The label's WARNINGS section, cross-referenced for 'Hepatotoxicity', was not fetched, and there is no UK SPC in this bundle. Verify against the manufacturer SPC (eMC) before use in hepatic impairment.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • US label CONTRAINDICATIONS: 'Known hypersensitivity (e.g., anaphylactic reactions and serious skin reactions) to diclofenac or any components of the drug product'
  • US label CONTRAINDICATIONS: 'History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. Severe, sometimes fatal, anaphylactic reactions to NSAIDs have been reported in such patients.'
  • US label CONTRAINDICATIONS: 'In the setting of coronary artery bypass graft (CABG) surgery'
  • NOTE: these are the only three contraindications in the fetched US label. UK labelling for diclofenac carries further contraindications (e.g. active GI ulceration/bleeding, severe hepatic/renal/cardiac failure, established cardiovascular disease, third trimester of pregnancy) that are NOT in this bundle — confirm against the manufacturer SPC (eMC).

Side effects

  • Adverse reactions the label flags as discussed in detail in its WARNINGS section (that section itself was not fetched): cardiovascular thrombotic events; GI bleeding, ulceration and perforation; hepatotoxicity; hypertension; heart failure and oedema; renal toxicity and hyperkalaemia; anaphylactic reactions; serious skin reactions; haematologic toxicity
  • Clinical trials experience (verbatim): 'In 718 patients treated for shorter periods, i.e., 2 weeks or less, with diclofenac potassium tablets, adverse reactions were reported one-half to one-tenth as frequently as by patients treated for longer periods.'
  • Clinical trials experience (verbatim): 'In a 6-month, double-blind trial comparing diclofenac potassium tablets (N = 196) versus diclofenac sodium delayed-release tablets (N = 197) versus ibuprofen (N = 197), adverse reactions were similar in nature and frequency.'
  • Most frequent adverse experiences: the label states that in patients taking diclofenac potassium tablets or other NSAIDs, the most frequently reported adverse experiences occurring in approximately 1% to 10% of patients are gastrointestinal — the list was CUT at the source-fetch limit immediately after the word 'Gastrointestinal', so the individual reactions and any non-GI categories were not retrieved. Treat this side-effect list as incomplete and confirm against the manufacturer SPC (eMC).

Monitoring

  • Not stated — no monitoring instruction appears in any section retrieved for this bundle (DOSAGE AND ADMINISTRATION, CONTRAINDICATIONS and a truncated ADVERSE REACTIONS). The WARNINGS section, which the label cross-references for cardiovascular, GI, hepatic, hypertensive, cardiac-failure, renal/hyperkalaemia, anaphylactic, dermatological and haematologic risks, was not fetched.
  • The only dosing-related instruction that was retrieved (US label, DOSAGE AND ADMINISTRATION): 'Use the lowest effective dose for the shortest duration consistent with individual patient treatment goals' and 'After observing the response to initial therapy... the dose and frequency should be adjusted to suit an individual patient's needs.'

Clinical monograph

How it works

It non-selectively inhibits cyclo-oxygenase (COX-1 and COX-2), reducing prostaglandin synthesis and thereby its analgesic, anti-inflammatory and antipyretic effects; the potassium salt dissolves quickly for faster onset than the sodium salt.

Prescribing in practice

  • Diclofenac carries a higher cardiovascular thrombotic risk than other non-selective NSAIDs and is contraindicated in established ischaemic heart disease, cerebrovascular disease, peripheral arterial disease and heart failure (MHRA advice); use the lowest effective dose for the shortest duration.
  • Co-prescribe gastroprotection (e.g. a proton-pump inhibitor) in patients at risk of gastrointestinal ulceration or bleeding, and avoid combining with other NSAIDs including aspirin.
  • Avoid in the third trimester of pregnancy and use caution with renal impairment, hypertension and concurrent ACE inhibitors, diuretics or anticoagulants.

Monitoring

Monitor blood pressure, renal function and for signs of gastrointestinal bleeding, particularly in older patients and those on longer courses.

Counselling the patient

  • Take with or after food to reduce stomach upset.
  • Stop and seek advice if you develop black stools, vomiting blood, or unexplained breathlessness or chest pain.

Evidence & guidelines

Diclofenac is a long-established NSAID whose cardiovascular safety profile is summarised in MHRA/EMA reviews and reflected in NICE guidance on NSAID prescribing.

Reference: NICE NG100; NICE NG88; MHRA Drug Safety Update; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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