M: Musculo-skeletal system
ATC group M holds drugs for the musculo-skeletal system: anti-inflammatory and antirheumatic products, muscle relaxants, antigout preparations and drugs for bone diseases [1].
| Description | In plain terms | Example drug | |
|---|---|---|---|
| M01 | Antiinflammatory and antirheumatic products | Ibuprofen (M01AE01) / naproxen (M01AE02) | |
| M02 | Topical products for joint and muscular pain | Topical diclofenac (M02AA15) / topical ketoprofen (M02AA10) | |
| M03 | Muscle relaxants | Rocuronium bromide (M03AC09) for neuromuscular block / baclofen (M03BX01) for spasticity | |
| M04 | Antigout preparations | Allopurinol (M04AA01) / febuxostat (M04AA03) | |
| M05 | Drugs for treatment of bone diseases | Alendronic acid (M05BA04) / denosumab (M05BX04) | |
| M09 | Other drugs for disorders of the musculo-skeletal system | leftover bone, joint and muscle drugs | Nusinersen (M09AX07) and risdiplam (M09AX10), for spinal muscular atrophy |
Topical products for joint and muscular pain
Within M02, M02AA holds non-steroidal anti-inflammatory drugs (NSAIDs) for topical use [1]. How NSAIDs work, and how their effect on pain is measured, is described on the M01 page.
For diclofenac sodium topical gel (M02AA15), the presumed site of action is local, in the skin and the joint fluid (synovial fluid). FDA scientists note that showing bioequivalence for dermatological products with a comparative clinical endpoint study can be costly, and that the study may not be sensitive enough to detect some formulation differences. The US FDA approved a generic diclofenac sodium topical gel on the totality of the evidence, which included an in vivo bioequivalence study with pharmacokinetic endpoints. In place of a comparative clinical endpoint study in patients, the evidence included a virtual bioequivalence assessment with dermal physiologically based pharmacokinetic (PBPK) modeling. The model related diclofenac exposure in plasma to exposure in skin and synovial fluid, and showed bioequivalence at the presumed site of action [2].