1. Clinical Overview
A fixed-dose combination (FDC) of a selective COX-2 inhibitor (Etoricoxib) and a centrally-acting muscle relaxant (Thiocolchicoside). It provides synergistic action for the management of acute painful musculoskeletal conditions by reducing inflammation, pain, and associated muscle spasm. This combination is widely used in India for conditions like low back pain, cervical spondylosis, and post-operative orthopedic pain.
| Onset | Duration | Bioavailability |
|---|---|---|
| Etoricoxib: 24 minutes for onset of analgesia. Thiocolchicoside: 30-60 minutes for onset of muscle relaxation. | Etoricoxib: Up to 24 hours (once-daily dosing). Thiocolchicoside: 6-8 hours. | Etoricoxib: ~100%. Thiocolchicoside: ~100% (oral). |
2. Mechanism of Action
The combination works via two distinct but complementary pathways. Etoricoxib selectively inhibits the cyclooxygenase-2 (COX-2) enzyme, reducing the synthesis of prostaglandins (PGs) at sites of inflammation, thereby decreasing pain, swelling, and fever. Thiocolchicoside acts as a centrally-acting muscle relaxant by competitively antagonizing strychnine-sensitive glycine receptors in the brainstem and spinal cord, and also potentiating GABA-A receptor-mediated inhibitory neurotransmission, leading to reduced muscle tone and spasm.
3. Indications & Uses
- Acute low back pain with muscle spasm
- Cervical spondylosis with radiculopathy/myofascial pain
- Post-operative orthopedic pain (e.g., after spinal surgery, joint replacement)
- Musculoskeletal trauma (sprains, strains)
4. Dosage & Administration
Adult Dosage: One tablet (Etoricoxib 60mg + Thiocolchicoside 4mg) twice daily, after meals. Maximum duration: 7-10 days.
Administration: Take with or after food to minimize gastrointestinal upset. Swallow whole with a full glass of water. Do not crush or chew. The tablet can be split if scored. Use for the shortest duration necessary to control symptoms.
5. Side Effects
Common side effects may include:
- Nausea
- Dyspepsia
- Heartburn
- Abdominal pain
- Diarrhea
- Headache
- Dizziness
- Drowsiness/sedation (due to thiocolchicoside)
- Dry mouth
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin, Acenocoumarol | Increased risk of bleeding due to additive antiplatelet effect of etoricoxib and protein binding displacement. | Major |
| Aspirin (low-dose cardioprotective) | Increased risk of GI ulceration and bleeding. May attenuate cardioprotective effect of aspirin. | Major |
| Lithium | Etoricoxib can decrease renal clearance of lithium, leading to lithium toxicity. | Major |
| Methotrexate | Etoricoxib may reduce renal clearance of methotrexate, increasing risk of bone marrow suppression. | Major |
| Diuretics (Furosemide, Thiazides) | Reduced diuretic and antihypertensive efficacy. Increased risk of renal impairment. | Moderate |
| ACE Inhibitors (Ramipril, Enalapril) / ARBs (Losartan) | Reduced antihypertensive efficacy. Increased risk of renal impairment, especially in volume-depleted patients. | Moderate |
| Corticosteroids (Prednisolone) | Significantly increased risk of GI ulceration and bleeding. | Major |
| SSRIs (Fluoxetine, Sertraline) | Increased risk of upper GI bleeding. | Moderate |
| Rifampicin | Decreases etoricoxib plasma levels by inducing CYP enzymes. | Moderate |
| Ketoconazole, Fluconazole | Increases etoricoxib plasma levels by inhibiting CYP3A4. | Moderate |
| Other CNS Depressants (Alprazolam, Clonazepam, Alcohol) | Additive sedation and dizziness with thiocolchicoside. | Moderate |
7. Patient Counselling
- Do take the medicine after food.
- Do inform your doctor about all other medicines you are taking, including over-the-counter pills, vitamins, and herbal products.
- Do report any history of heart, kidney, liver, or stomach problems.
- Do not take if you are pregnant, planning pregnancy, or breastfeeding.
- Do not exceed the prescribed dose or duration.
- Do not consume alcohol while on this medication.
- Do not drive or operate heavy machinery if you feel dizzy or drowsy.
- Do not take this medicine for fever or flu-like symptoms.
8. Toxicology & Storage
Overdose: Etoricoxib: Lethargy, drowsiness, nausea, vomiting, epigastric pain, GI bleeding, hypertension, acute renal failure, respiratory depression, coma. Thiocolchicoside: Enhanced CNS depression (profound drowsiness, ataxia, hypotonia), respiratory depression, coma.
Storage: Store below 30°C. Protect from light and moisture. Keep the container tightly closed. Keep out of reach and sight of children.