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The effects of adherence to non-steroidal anti-inflammatory drugs and factors influencing drug adherence in patients with knee osteoarthritis

Clinical Research 10 min 19

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Created On: 10/10/2019

The effects of adherence to non-steroidal anti-inflammatory drugs and factors influencing drug adherence in patients with knee osteoarthritis

The major reasons for morbidity, disability, and loss of function mainly in elderly people is Knee osteoarthritis (OA).

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Key take away

The study indicates that patients with better adherence to NSAIDs showed better outcomes compared to those with the poor adherence.

Background

The major reasons for morbidity, disability, and loss of function mainly in elderly people is Knee osteoarthritis (OA). It significantly affects the quality of life of the patients with persisting disease. OA is likely to become the 4th prime reason of global disability by 2020. The medications for OA like simple analgesics (acetaminophen and NSAIDs) mainly provides symptomatic relief. Currently there are no effective medications to slow down the progression of OA. However, NSAIDs do not prevent the disease progression, but certainly helps in relieving pain and improves quality of life by blocking nociceptors. The adherence to arthritis medications is known to be low. Dosing frequency, pain and self-efficacy levels, and physician trust are the usual factors in adherence to OA with other rheumatoid diseases. One of other studies had recently found that side effect, out of pocket costs, mode of action, and treatment schedule also poses a considerable effect on the choice to continue medication.

Rationale behind research:

There is little information about OA patient’s treatment adherence and differences resulting from NSAIDs Therefore, this study was conducted to investigate the drug adherence and patient reported outcomes

Objective:

The objectives of this study were:

To assess the differences in patient reported outcomes according to the drug adherence
To evaluate the factors affecting them

Method

Baseline: In comparison between the adherent and non-adherent group, there was difference in the distribution of age group whereas, other factors did not show significant differences in their distribution.

Outcomes

For the reasons for no strict adherence, 464 patients answered the question (355 patients chose one answer, 93 chose 2 answers, 14 chose 3 answers, and 2 chose 4 answers). The top three reasons were: “My symptom has gone better” (21.5%); “Osteoarthritis medication is thought to be only a pain relief” (16.4%); and “It causes indigestion, discomfort, heart burn, and other GI events” (13.0%).
All clinical outcomes including pain NRS, KOOSK and EQ-5D were significantly improved at the follow-up compared to the baseline in total patients group, adherent group, and non-adherent group. Comparison of the clinical outcomes between the adherent group and non-adherent group showed no significant differences in any of the baseline variables except for pain NRS (6.1 ± 1.5 vs. 6.4 ± 1.6, P = 0.027), while, at follow-up, pain NRS (4.3 ± 1.9 vs. 4.9 ± 2.2, P = 0.003), KOOSK symptom (74.3 ± 16.7 vs. 71.6 ± 17.0, P = 0.048), KOOS-K pain (68.6 ± 16.4 vs. 64.9 ± 16.6, P = 0.005), and KOOS-K ADLs score (68.9 ± 16.4 vs. 64.8 ± 17.3, P = 0.003) were significantly higher in the adherent group than non-adherent group.

Figure 1: Clinical outcomes of adherent group at baseline and after 3 weeks follow up

Figure 2: Clinical outcomes of non-adherent group at baseline and after 3 weeks follow up

In logistic regression analysis identifying the factors that affect adherence, elderly patients (70-74 years old and 75-79 years old) and male patients were found to be more adherent, while educational status, frequency of daily NSAIDs administration, duration of knee OA, and other factors did not affect adherence

Result

Outcomes

For the reasons for no strict adherence, 464 patients answered the question (355 patients chose one answer, 93 chose 2 answers, 14 chose 3 answers, and 2 chose 4 answers). The top three reasons were: “My symptom has gone better” (21.5%); “Osteoarthritis medication is thought to be only a pain relief” (16.4%); and “It causes indigestion, discomfort, heart burn, and other GI events” (13.0%).
All clinical outcomes including pain NRS, KOOSK and EQ-5D were significantly improved at the follow-up compared to the baseline in total patients group, adherent group, and non-adherent group. Comparison of the clinical outcomes between the adherent group and non-adherent group showed no significant differences in any of the baseline variables except for pain NRS (6.1 ± 1.5 vs. 6.4 ± 1.6, P = 0.027), while, at follow-up, pain NRS (4.3 ± 1.9 vs. 4.9 ± 2.2, P = 0.003), KOOSK symptom (74.3 ± 16.7 vs. 71.6 ± 17.0, P = 0.048), KOOS-K pain (68.6 ± 16.4 vs. 64.9 ± 16.6, P = 0.005), and KOOS-K ADLs score (68.9 ± 16.4 vs. 64.8 ± 17.3, P = 0.003) were significantly higher in the adherent group than non-adherent group.

Figure 1: Clinical outcomes of adherent group at baseline and after 3 weeks follow up

Figure 2: Clinical outcomes of non-adherent group at baseline and after 3 weeks follow up

In logistic regression analysis identifying the factors that affect adherence, elderly patients (70-74 years old and 75-79 years old) and male patients were found to be more adherent, while educational status, frequency of daily NSAIDs administration, duration of knee OA, and other factors did not affect adherence

Conclusion

In this study, both adherent and non-adherent groups showed significantly improved outcomes after 3 weeks of medication treatment, but most of the follow-up outcomes were significantly better in the adherent group as hypothesized. Of those factors affecting the adherence to NSAIDs, older patients and male patients showed better adherence, while educational status, frequency of daily NSAIDs administration did not show difference in adherence.

In this study, there was relatively high drug adherence with the patients group, which is inconsistent with the previous studies (approximately 10% of low adherence rate). The reasons for the relatively higher adherence in the present study may include: 1) Targeting relatively older patients 2) Studying a relatively short period compared to long-term treatment of OA or 3) that it was a self-survey study which could show a relatively higher adherence than monitoring study depending on the patients’ characteristics.

Limitations

The scope of study was limited to Korean patients, with predominantly female group representing unique gender distribution in the knee OA patients in Korea and a cultural difference of the patient’s attitude towards the doctor
The results of the data analyses using many variables such as all different types of NSAIDs, radiologic severity, symptom duration, pain intensity, or previous analgesic medication history were not included

Clinical take-away

This study can definitely contribute to the patient education for the pharmacological treatment in knee OA patients as the patients with better adherence to NSAIDs showed better outcomes compared to those with the poor adherence.