Condition Focus: Rheumatoid Arthritis — Dose Optimisation and Methotrexate Comparison
This dose-comparison study from Al Musawi and Alsudani addresses one of the most practical questions in PBM device design: how much energy density produces the best anti-inflammatory results? Using a collagen-induced RA model in rats, the researchers compared three PBM doses (36, 54, and 72 J/cm²) against each other and against methotrexate — the gold-standard disease-modifying drug for RA.
The key finding: 54 J/cm² produced optimal anti-inflammatory results comparable to methotrexate, with reduced paw thickness (edema), increased superoxide dismutase (SOD) activity (antioxidant defense), and modulated cytokine levels. The lower dose (36 J/cm²) was suboptimal, and the higher dose (72 J/cm²) did not improve upon the 54 J/cm² results — consistent with the biphasic dose-response (Arndt-Schulz curve) that characterises PBM: too little is insufficient, too much provides no additional benefit or can even be inhibitory.
The comparison against methotrexate is significant because methotrexate is a serious drug with significant side effects (liver toxicity, immunosuppression, bone marrow effects). Demonstrating comparable anti-inflammatory outcomes with a non-pharmacological intervention reinforces PBM’s positioning as a therapeutic alternative, not just a complementary add-on.
For gout, while the G.O.A.T. targets a lower fluence (4 J/cm²), this study demonstrates the principle that dose matters and confirms the biphasic response pattern. The antioxidant (SOD) activation is also relevant: gout is characterised by excessive oxidative stress, and SOD is one of the key enzymes that neutralises the reactive oxygen species driving NLRP3 activation.
G.O.A.T. for Gout Alignment:
While the G.O.A.T. operates at 4 J/cm² (lower than the 54 J/cm² optimum here), the biphasic dose-response principle applies across different tissue types and conditions. The SOD activation and cytokine modulation support the G.O.A.T.’s dual-mechanism approach: anti-inflammatory + antioxidant.
Link to original research here
Editor’s note: The dose-response principle demonstrated here is explained mechanistically by the Arndt-Schulz curve in Huang et al 2009. The antioxidant activation (SOD) parallels the oxidative stress reduction in knee OA shown in Yamada et al 2020. The edema component measured here is objectively confirmed in Chia et al 2025. For the wavelength-dependent edema response, see Fonseca et al 2025.
Related Articles
- Biphasic Dose Response in PBM: Arndt-Schulz Curve – Huang et al 2009
- PBM Reduces Oxidative Stress and Inflammation in Knee OA – Yamada et al 2020
- PBM on Swelling Reduction and Recovery in TKA – Chia et al 2025
- PBM on RA and OA: Edema and Vascular Permeability – Fonseca et al 2025
- PBM and Oxidative Stress: Mitochondrial Activity Regulation – 2022
Key Takeaways
- 54 J/cm² identified as optimal dose — comparable to methotrexate for anti-inflammatory outcomes
- Biphasic response confirmed: 36 J/cm² insufficient, 72 J/cm² no additional benefit
- SOD antioxidant activation — relevant to gout’s oxidative stress-driven NLRP3 cascade
- PBM comparable to a serious RA drug without the liver, bone marrow, and immune side effects
Study Overview
| Study Type: | Controlled animal study (dose-comparison) |
| Wavelength(s): | Not specified in abstract |
| Treatment Protocol: | 3 dose groups: 36, 54, 72 J/cm²; collagen-induced RA model |
| Sample Size: | Multiple rat groups (3 dose + methotrexate + control) |
| Primary Outcome: | 54 J/cm² optimal: paw thickness↓, SOD↑, cytokines modulated, comparable to methotrexate |
Full Citation
Al Musawi MS, Alsudani AM. (2026). Photobiomodulation for reducing rheumatoid arthritis using different energy densities. Photobiomodulation Journal. View Publication
