A fixed-dose combination (FDC) of a non-steroidal anti-inflammatory drug (NSAID) and a centrally-acting skeletal muscle relaxant. Diclofenac provides analgesic and anti-inflammatory effects by inhibiting prostaglandin synthesis, while Metaxalone acts on the central nervous system to relieve muscle spasm and associated pain. This combination is specifically targeted for the management of acute, painful musculoskeletal conditions where both inflammation and muscle spasm are present. The FDC is designed to improve compliance by reducing pill burden.
Adult: One tablet (Diclofenac 50mg + Metaxalone 400mg) two to three times daily, after meals. The lowest effective dose for the shortest duration should be used.
Note: Take with or immediately after food with a full glass of water to minimize gastrointestinal irritation. Do not crush or chew. Swallow whole. Do not lie down for at least 10 minutes after taking the dose.
The combination exerts a synergistic effect. Diclofenac inhibits the enzyme cyclooxygenase (COX-1 and COX-2), thereby blocking the conversion of arachidonic acid to prostaglandins, thromboxanes, and prostacyclins. This reduces inflammation, pain, and fever at the peripheral site. Metaxalone's exact mechanism is not fully elucidated but is believed to act primarily on the central nervous system, possibly by depressing polysynaptic reflexes in the spinal cord and subcortical areas of the brain, leading to skeletal muscle relaxation without directly affecting neuromuscular junctions or muscle fibers.
Pregnancy: Category C (first and second trimester) and Category D (third trimester). Avoid, especially in third trimester due to risk of premature closure of ductus arteriosus, oligohydramnios, and prolonged labor. Use only if potential benefit justifies potential fetal risk.
Driving: May impair mental and/or physical abilities. Dizziness, drowsiness, and blurred vision are common. Patients should be cautioned against driving or operating machinery until their response is known.
| Anticoagulants (Warfarin, Acenocoumarol) | Increased risk of bleeding due to antiplatelet effect of diclofenac and protein binding displacement | Major |
| Anti-platelets (Aspirin, Clopidogrel) | Increased risk of GI bleeding | Major |
| Other NSAIDs or COX-2 Inhibitors (Ibuprofen, Celecoxib) | Increased risk of GI and renal toxicity; no therapeutic advantage | Major |
| Corticosteroids (Prednisolone) | Markedly increased risk of GI ulceration | Major |
| SSRIs/SNRIs (Fluoxetine, Venlafaxine) | Increased risk of upper GI bleeding | Moderate |
| ACE Inhibitors/ARBs (Ramipril, Telmisartan) | Reduced antihypertensive effect; risk of worsened renal function | Moderate |
| Diuretics (Furosemide, Hydrochlorothiazide) | Reduced diuretic and antihypertensive efficacy; nephrotoxicity risk | Moderate |
| Lithium | Increased serum lithium levels and toxicity risk | Major |
| Methotrexate | Increased methotrexate levels and toxicity risk | Major |
| Cyclosporine | Increased nephrotoxicity risk | Major |
| Antidiabetics (Glibenclamide, Metformin) | Possible hypoglycemia or hyperglycemia | Moderate |
| CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive sedation and dizziness with metaxalone | Major |
Same composition (Diclofenac (50mg) + Metaxalone (400mg)), different brands: