Oral vs. topical NSAID for OA pain - how and why people choose treatments
Two papers published early online in the BMJ compare the value of a topical NSAID (ibuprofen gel) with oral use of the same drug for knee pain due to osteoarthritis (OA). The first paper describes two trials: a RCT comparing the effect of advice to use topical ibuprofen with advice to use oral ibuprofen (n=282), and a preference trial (n=303) in which the patients selected the route of delivery (topical or oral). The second paper describes a qualitative study exploring the reasons for these patients’ preferences.
The RCT and preference trial was conducted in 26 general practices in the UK and involved 585 patients aged 50 and older. Participants were offered the choice of joining the RCT or the preference study. Those in the RCT (n=282) were randomised and those in the latter study (n=303) selected their treatment route. They were given starter packs and thereafter, the medication could be either prescribed or bought over the counter. They were followed up with postal questionnaires at 3, 6, 12, and 24 months after study entry. Nurse assessments and blood tests also took place at 12 and 24 months. Follow-up questionnaires at 12 months were used for the primary efficacy analyses and the primary efficacy outcome measure was the WOMAC (Western Ontario and McMaster Universities) VA 3.1 questionnaire, which measures knee pain and disability in the preceding 48 hours and produces individual measures of pain, stiffness, and physical function and a global assessment.
The following findings were reported:
- WOMAC scores changed little between baseline and the 12 months follow-up in the oral and topical group in the randomised and the preference trial.
- There were no significant differences in the WOMAC global score changes between topical or oral groups in either study.
- There were no differences in major adverse effects in either study.
- The only significant differences in secondary outcomes were in the RCT: the oral group had more respiratory adverse effects (17% v 7%) and the change in serum creatinine was 3.7 mmol/l less favourable, and more participants changed treatments because of adverse effects (16% v 1%).
- In the topical group more participants had chronic pain grade III or IV at three months, and more participants changed treatment because of ineffectiveness.
In terms of patient characteristics, more people in the preference study opted for topical (n=224) than for oral treatment (n=79), though those with more severe or widespread pain chose oral treatment. Those that chose topical tended to be older and of lower social class. Those who chose oral NSAIDs seemed to be more tolerant of their adverse effects than those randomised to the oral group, even though those in the preference study took more oral NSAIDs.
The researchers concluded “the outcome for knee pain at 1 year is equivalent, whether patients are initially advised to use oral or topical treatment. This was a consistent finding in both the RCT and the preference study.”
The qualitative study explored the factors that influenced the decisions of the participants to take part in the study and their use of topical or oral ibuprofen for their knee pain. It obtained information through a telephone interview from 15 of the participants and a second interview with a different set of participants’ (n=15) was conducted in their home or GP practice, according to which study they had joined and their choice of treatment or allocated treatment in the trial, and whether it had an adverse effect. Sixteen and 14 had used topical and oral NSAIDs, respectively.
The study found that participants’ decision making was influenced by five themes:
- Perceptions of the associated risk of adverse effects
- Presence of other illness
- Nature of their pain
- Advice received,
- Practicality
This qualitative study supported the findings of the RCT and preference study that patients with mild, transient knee pain preferred to use topical preparations, whilst oral NSAIDs was preferred by those with more serious, constant or widespread pain. The researchers concluded that though the participants’ understanding of how the medications worked was sometimes poor, their decision making about the use of NSAIDs seemed logical and appropriate, and based on the nature of pain, risk of adverse effects, advice, and practicalities. They add that taking such views into account when prescribing may improve adherence, judgement of efficacy, and the doctor-patient relationship.
According to an accompanying editorial, these data suggest that given options, patients will make sensible rational choices about how they want to be treated, and that their ability to choose may improve efficacy and reduce toxicity. Furthermore, topical NSAIDs are a viable safe alternative to oral NSAIDs for the treatment of osteoarthritis of the knee, even if a placebo effect explains most of the value of these topical agents.
Br Med J 2008; 336: 138-42 (RCT and preference study, link to abstract);
Br Med J 2008; 336: 142-45 (qualitative study, link to abstract);
Br Med J 2008; 336: 105-6 (Editorial; link to extract)
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