Supported by an unrestricted education grant from Haleon Australia Pty Ltd.

Learning objectives

After reading this article, pharmacists should be able to: 

  • Identify indications for over-the-counter supply of diclofenac and requirements associated with its supply
  • Discuss safety considerations associated with diclofenac
  • Describe clinical factors that pharmacists need to consider when determining if diclofenac is appropriate for a patient.

Competencies (2016) addressed: 1.1, 1.4, 1.5, 1.6, 3.1, 3.2, 3.5, 3.6

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Introduction

Pharmacists are well equipped to assist patients who request treatment for pain. This article discusses the role of the pharmacist in the appropriate supply of over-the-counter diclofenac for management of pain.

Pain in perspective

Pain is subjective. While no two people experience pain in exactly the same way, it is very common. Data indicates that in 2020–21, 71.1% of Australian adults experienced recent bodily pain and for 6.4% of those people it was severe or very severe.1 Pain can have an important, negative impact on overall quality of life, including emotional and social interactions and ability to function at work.1,2 It has been estimated that chronic pain cost the Australian economy more than $139 billion in 2018.3

Australians tend to self-diagnose and self-manage their pain, with many opting to use non-prescription medicines. When asked, over half of patients using analgesics would like to know more about potential risks and adverse effects associated with their medicines.4 This provides an ideal opportunity for pharmacists to get involved and discuss pain and appropriate pain management options with their patients.

Taking steps to ensure patients are educated on the appropriate use of a non-steroidal anti-inflammatory drug (NSAID) such as diclofenac – including indications, dose, duration of use and potential adverse effects – will promote the principles of quality use of medicines (QUM) and ensure its appropriate use.

Appropriate supply of Pharmacist Only (Schedule 3) medicines

Unlike many other countries, community pharmacy in Australia has different pharmacy over-the-counter (OTC) medicine classifications: Pharmacy medicine (Schedule 2) and Pharmacist Only medicine (Schedule 3).

Schedule 2 medicines are those that may require advice from a pharmacist to support safe and effective use, while Schedule 3 medicines need the advice of a pharmacist to support their safe and appropriate use.5

Table 1 – Oral diclofenac: Schedule 2 and Schedule 3 products in Australia

Schedule  Common indications Common dosage instructions (dosing instructions vary between products, consult individual product information)
Schedule 2 

Pharmacy medicine 

Oral diclofenac 12.5 mg in pack sizes of 20 or less dosage units, labelled with a recommended daily dose of 75 mg or less

 Temporary relief of painful conditions such as headache, dental pain, period pain, rheumatic and muscular pain, backache

Temporary relief of symptoms of colds and flu (e.g. aches and pains, sore throat) Fever reduction

 Diclofenac 12.5 mg

A typical dose is 2 tablets when symptoms appear, If needed, further doses of 1 or 2 tablets every 4 to 6 hours may be taken. No more than 6 tablets (75mg) should be taken in a 24-hour period. 

Maximum daily dose (MDD): 75 mg

Duration of use: a few days only 
Schedule 3 

Pharmacist Only medicine 

Oral diclofenac 25 mg in pack sizes of 30 or less dosage units

 As short-term treatment for the relief of acute pain states in which there is an inflammatory component Diclofenac 25 mg The usual dose is 2 tablets initially, followed by either 1 or 2 tablets every 8 hours. 

MDD: 150 mg

Duration: a few days

For milder cases and children over 14 years: 1 to 2 tablets initially, followed by 1 tablet every 8 hours, is usually sufficient.

MDD: 100 mg

Duration: a few days
Symptomatic treatment of primary dysmenorrhoea In primary dysmenorrhoea, initially a dose of 50–100 mg should be taken followed by 50 mg three times daily when required, up to a maximum of 200 mg per day.

Treatment should begin when symptoms first appear and, depending on their duration and severity, be continued for up to 3 days.

MDD: 200 mg

Duration: 3 days
Treatment of acute migraine attacks (with or without aura) In migraine, an initial dose of 50 mg should be taken at the first signs of a migraine. If the pain is not relieved within 2 hours of this initial dose, a further dose of 50 mg may be taken. If needed, further doses of 50 mg may be taken at intervals of 4–6 hours (to a maximum dose of 200 mg per day)

MDD: 200 mg

Duration: a few days (one attack)

Quality use of medicines, NSAIDs and oral diclofenac

In Australia, there are two oral diclofenac strengths (12.5 mg and 25 mg) available in two different non-prescription classification schedules: Schedule 2 and Schedule 3 respectively (see Table 1).

These products have different labelled indications and dosing instructions. QUM dictates that when using NSAIDs, a strategy of lowest effective dose for the shortest period of time be maintained.6 Whether being used as a Schedule 2 or Schedule 3 medicine, oral diclofenac should be used for temporary relief and not be taken for more than a few days at a time.7

The Schedule 3 availability of the higher dose strength of oral diclofenac ensures that this medicine can be used according to QUM principles and a qualified pharmacist is involved in assessing individual therapeutic need and risk.

Diclofenac data overview

The clinical efficacy of oral diclofenac in acute pain conditions is widely established. Data from single dose studies with diclofenac potassium has been evaluated in three Cochrane meta-analyses.8-10

The data in these meta-analyses support a dose-response relationship, with lower (more favourable) number needed to treat (NNT) when higher doses of diclofenac are administered (see Table 2).

The standard measure of NNT for additional benefit is used widely to report the magnitude of the effect of an intervention.11 In this case it describes the number of participants in studies who need to be treated with an analgesic for one more person to have good pain relief than if the same number had been treated with placebo. Lower numbers for NNT are better.

Table 2 – Summary of meta-analysis of studies in diclofenac potassium showing at least 50% maximum pain relief over 6 hours compared with placebo

Dose  Participants and studies included Relative benefit (95% Cl)  NNT (95% Cl) 
25 mg N = 502 (4 studies) 3.9 (2.8 to 5.3) 2.4 (2.0 to 2.9)
50 mg N = 757 (7 studies) 3.7 (2.9 to 4.7)  2.1 (1.9 to 2.5)
100 mg  N = 594 (6 studies) 4.8 (3.6 to 6.5) 1.9 (1.7 to 2.3)
NNT = number needed to treat N = number of participants Reference: Derry8

How effective is OTC diclofenac for managing pain?

Inflammatory pain – ankle sprains

Ankle sprains are common musculoskeletal injuries – after back pain they are the second most common orthopaedic complaint.12 Healing occurs in three distinct phases – inflammatory, reparative, and remodelling.13 The inflammatory phase is the initial response to injury and usually lasts 24–72 hours. Ligament healing can be expedited by an initial treatment protocol that minimises pain, inflammation, and swelling and incorporates early controlled motion.13

A meta-analysis of data from 22 studies has shown that NSAIDs are superior to placebo in reducing short-term pain on weight-bearing, pain at rest and swelling.14 Outcome data from the three trials with diclofenac potassium in ankle sprains supports its use for the short-term management of this type of pain (see Table 3).

Migraine

Migraine is a common disorder characterised by attacks of moderate to severe throbbing headaches that are often unilateral, worsened by physical activity, and associated with nausea and/or vomiting, photophobia, and phonophobia.18 It is ranked second highest among specific causes of disability globally.19 Migraine treatment strategies include preventive therapy (to reduce frequency and severity of attacks) and acute therapy used to abort an attack.6

Table 3 – Outcome data from trials with diclofenac potassium in ankle sprains 

Study Dose (mg) Outcomes 

(% of patients receiving diclofenac vs placebo)
Pain reduction Inflammation reduction Rescue medication
Morán 1990 50 TID 78% vs 61% 86% vs 44% 2.8% vs 69.4%
Morán 1991 50 TID 85% vs 36.8% 100% vs 16% 0% vs 31.6%
Bahamonde 1990 50 TID P<0.0001* 6.9% vs 80.6%
TID = three times daily *statistically significant in favour of diclofenac  References: Morán16; Morán16; Bahamonde17

The efficacy of an acute treatment should usually be determined by the proportion of patients who are headache-free 2 hours post dose; sustained pain relief at 24–48 hours is considered to be the ideal response and is also an important outcome for patients.18

A meta-analysis of data from several studies has shown oral diclofenac potassium 50 mg to be effective versus placebo in a number of different measures (see Table 4).20

Dysmenorrhoea

Dysmenorrhoea is a common gynaecological complaint, which affects approximately 72% of Australian women of reproductive age.21 Recent Australian research of young women found that a higher proportion experience moderate (49%) and severe (32%) pain than those that experience mild pain (19%).22 A meta-analysis of data from several studies has shown diclofenac to be effective versus placebo at varying doses in a number of different measures (see Table 5).23

What are the risks associated with OTC diclofenac?

Common adverse effects associated with diclofenac include nausea, dyspepsia, gastrointestinal ulceration and bleeding, raised liver enzymes, diarrhoea, headache, dizziness, salt and fluid retention, and hypertension.6

The risk of cardiovascular events during prescription NSAID treatment has been extensively studied. Data from meta-analyses and single studies demonstrate an increased risk of cardiovascular thrombotic events (e.g. myocardial infarction and stroke) associated with the use of diclofenac, particularly at high doses (≥150 mg daily) and with long-term treatment.24 The serious adverse effects associated with NSAID use have been shown to be exposure driven, and appear to be associated with dose and duration.24,25

It has been suggested that safety concerns with NSAIDs in the prescription setting could be applicable to OTC products, particularly if they are inappropriately overused (i.e. higher doses for durations of 14 days or more).26 However, there are no studies that have been specifically designed to assess cardiovascular risk in populations of OTC diclofenac users under OTC conditions. While some research has suggested that lower dose diclofenac used short term was not associated with serious adverse effects, caution is still required.14-24 Older research from the United States looked at 1,227 patients who received diclofenac 75–200 mg/day short term and found it to be generally well tolerated, with the most common adverse effects being diarrhoea and nausea.27 A 2015 meta-analysis comparing diclofenac with other NSAIDs in the management of arthritis found that major upper gastrointestinal adverse effects (e.g. ulcer, perforation, obstruction) were fewer with diclofenac treatment compared to naproxen and ibuprofen, but there was a similar risk of major cardiovascular events.28 In addition, two OTC dosing studies have reported no serious adverse cardiovascular events with diclofenac.29,30

Table 4 – Diclofenac potassium 50 mg versus placebo in migraine

Studies included* Outcome  Relative benefit NNT 
N = 1477 (2 studies) Pain-free at 2 hours 2.0 (1.6 to 2.6) 8.9 (6.7 to 13) 
N = 1477 (2 studies) Headache relief at 2 hours 1.5 (1.3 to 1.7) 6.2 (4.7 to 9.1)
N = 1578 (2 studies)  24-hour sustained pain-free 2.3 (1.7 to 3.0) 95 (7.2 to 14)
NNT = number needed to treat *meta-analyses are based on all diclofenac potassium data, irrespective of formulation N = number of participants  Reference: Derry20

All NSAIDs are associated with an increased risk of cardiovascular adverse effects, however, studies carried out over the years have had varied results in terms of the risk associated with specific NSAIDs; the evidence on this is still evolving.25

Current guidelines recommend avoiding diclofenac and COX-2 selective NSAIDs other than celecoxib in patients at an increased risk of cardiovascular toxicity.25 Current guidelines also note that short- term use of NSAIDs (less than 5 days) does not increase the risk of cardiovascular events significantly.25

Odom et al have extended previous research quantifying the NSAID dose–toxicity relationship by modelling dose as a continuous measure, allowing for an assessment of the risks of major gastrointestinal and cardiovascular events for patients taking specific diclofenac doses compared with NSAID nonusers.31 Analysis of data from seven studies, which contributed to 11 dose-specific risk ratio observations, showed a positive linear relationship between diclofenac dose and the relative risks of major gastrointestinal and cardiovascular events (see Table 6).

The magnitude of increased cardiovascular risk when using NSAIDs depends on the baseline cardiovascular risk; therefore, a larger effect is expected in high-risk populations, such as patients with established heart failure or a high cardiovascular risk profile.24,32

A study in France suggested that the population of non-prescription medication users who require effective analgesia for short-term, self-limiting conditions are more likely to be younger on average, with fewer additional prescription medicines, comorbidities and baseline risk factors.33

The European Society for Cardiology has recommended that ‘Non-aspirin NSAIDs should only be sold over the counter when measures are put in place to ensure that their use is accompanied by an appropriate warning of their frequent cardiovascular complications’.34 The Schedule 3 medicines category, which mandates pharmacist consultation prior to supply, addresses this need. In addition, Schedule 2 medicines can only be sold where pharmacist advice is available to patients, and provides an opportunity for the pharmacist to reinforce important safety information and counselling points.5

Table 5 – Diclofenac versus placebo in primary dysmenorrhoea

Studies* Outcome Odds ratio
N = 140 (3 studies) Pain relief  5.68 (3.03 to 10.67)
N = 24 (1 study) Additional analgesia required  0.06 (0.05 to 0.08)
N = 40 (1 study) Absence from school or work 0.07 (0.01 to 0.40)

*meta-analyses are based on all diclofenac data, irrespective of formulation Reference: Marjoribanks29 

Table 6 – Estimated risk of serious gastrointestinal and cardiovascular events relative to non-use of NSAIDs according to diclofenac dose

Diclofenac daily dose Estimated

gastrointestinal risk

ratio (SE; 95% CI)

 Estimated

cardiovascular risk

ratio (SE; 95% CI)
50 mg 1.89 (0.092; 1.68–2.10) 1.13 (0.022; 1.08–1.18)*
100 mg 2.78 (0.184; 2.36–3.19) 1.26 (0.044; 1.17–1.35)
150 mg 3.66 (0.275; 3.04–4.29) 1.39 (0.067; 1.25–1.53)

* The cardiovascular meta-regression model was based on a range of daily doses as low as 75mg; the cardiovascular risk ratios estimated for a daily dose of 50 mg oral diclofenac demonstrates applying the risk equation for doses not included in the model Reference: Odom31  

The risk of NSAID-related adverse effects is correlated to the dose and duration of use.25 It increases substantially in patients over 70 years of age 35 and is affected by individual risk factors, particularly for cardiovascular or gastrointestinal harm. It is important to ensure that each individual patient is assessed for risk.

Clinical considerations

Appropriate supply of diclofenac

Pharmacists need to establish whether diclofenac is the most suitable analgesic for an individual patient’s pain condition and, if it is, ensure that:

● the condition being managed is not a recurrent or long-standing pain state that would be better managed by a GP

● there are no factors in the patient’s medical history that would put them at increased risk of adverse effects.

Pharmacists should also consider the most appropriate formulation of diclofenac for the patient. Compared with enteric-coated diclofenac sodium tablets, diclofenac potassium achieves maximum plasma concentrations much faster and has demonstrated faster pain reduction.8

Box 1 outlines some key considerations for pharmacists when determining if diclofenac is suitable for a patient.

Box 1 – Practice guidelines for pharmacists

Check  Precautions – dehydration, asthma, coagulation disorders, elderly

Contraindications – active peptic ulcer disease or gastrointestinal bleeding, hypersensitivity to aspirin or other NSAIDs, severe renal or hepatic impairment, cardiovascular disease (e.g. heart failure), pregnancy and breastfeeding status
Consider Drug interactions: For example, lithium, corticosteroids, anticoagulants and antiplatelets, methotrexate, ciclosporin, phenytoin, diuretics and antihypertensives and medicines that increase potassium concentration

Triple whammy: NSAID + ACE inhibitor/angiotensin II receptor antagonist + diuretic – increased risk of renal dysfunction, hyperkalaemia and reduced antihypertensive effect
Advise patients of potential adverse effects Patient should stop taking diclofenac and see their doctor immediately if they experience any concerning adverse effects including:

gastrointestinal symptoms – black stools or dark coffee-coloured vomit

cardiovascular symptoms – swollen ankles or chest pain

respiratory symptoms – diffculty in breathing
When to refer  Red flag symptoms

Examples:

Primary dysmenorrhoea

● Heavy or unexplained bleeding

● Severe lower abdominal pain

● Women over the age of 30 presenting with new or worsening symptoms

Headache

● New or different type of headache

● Neck stiffness, fever, vomiting

● Speech difficulties, confusion, memory problems, balance problems, drowsiness, seizures

Back pain

● New back pain in people under 20 or over 55 years

● Pain not improving after 4 weeks or progressively worsening

● Pain following major trauma such as vehicle accident
When to review Provide a medication plan indicating when relief should be obtained and when to seek further advice.

References: Rossi6; eMIMS7; Knott36; Rutter37; Sansom38

Conclusion

Diclofenac is available over the counter in Australia and in this setting is indicated for certain pain conditions including ankle sprains, migraine and dysmenorrhoea. If diclofenac is determined to be suitable for a patient, it is important they are made aware of potential risks associated with its use and when they should seek medical advice if any adverse effects occur.

Key points

  • Pain affects many Australians.
  • Diclofenac is indicated for conditions such as inflammatory pain, migraine and primary dysmenorrhoea.
  • The dosing instructions for diclofenac 25 mg differ depending on the indication it is being used for.
  • Benefits and risks of diclofenac for an individual patient need to be considered before recommending its use.
  • Pharmacists must be involved in the supply of Schedule 3 medicines to ensure that they are used safely and appropriately.
1) How confident are you in counseling patients on the use of Diclofenac in the management of Pain (Open-ended)
2) Are you aware of the risks and side effects of the use of Diclofenac? (yes /no option)
3) How effective is Diclofenac for the management associated with (Tick a box)
– Inflammatory Pain
– Migraine
– Dysmenorrhea4) Which formulation of diclofenac provides faster pain reduction: (Tick a box option)
  • Diclofenac potassium
  • Enteric-coated diclofenac sodium

– Were you satisfied with the CPD module reviewed?
– Was the module easy to follow and understand?
– How likely are you to recommend Diclofenac to your patients?

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References

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  2. Dueñas M, Ojeda B, Salazar A, et al. A review of chronic pain impact on patients, their social environment and the health care system. J Pain Res 2016; 9:457­­–67.
  3. Australian Institute of Health and Welfare. Chronic pain in Australia. 2020. At: www.aihw.gov.au/reports/chronic-disease/chronic-pain-in-australia/summary
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Acknowledgement

Neil Petrie BPharm AACPA MPS (he/him) Consultant Pharmacist at PRN Consulting authored the original version of this article.

Our reviewers

TARA EDMONDS (she/her) BPharm MHA MPS PSA Professional Practice Pharmacist

CLARA FITTLER (she/her) BPharm GradCertAppPharmPrac CertIV TAE MPS PSA Professional Practice Pharmacist

SARUSHKA SRITHARAN (she/her) BPharm(Hons) DipMgt MPS PSA Professional Practice Pharmacist

CONFLICT OF INTEREST DECLARATION

The original author received editorial assistance from Hazel Palmer MSc, ISMPP CMPP, of Scriptix Pty Ltd, funded by the sponsor.

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