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# Diclofenac (Tablet)
## Overview
Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis. It is available as immediate-release (IR) and delayed-release (DR/enteric-coated) formulations.
## Primary Indications
* Osteoarthritis
* Rheumatoid arthritis
* Ankylosing spondylitis
* Mild to moderate pain or primary dysmenorrhea
## Adult Dosing
* **Osteoarthritis:** 100–150 mg daily in divided doses (e.g., 50 mg TID or 75 mg BID).
* **Rheumatoid Arthritis:** 150–200 mg daily in divided doses (e.g., 50 mg QID).
* **Ankylosing Spondylitis:** 100–125 mg daily (25 mg QID plus an optional 25 mg at bedtime).
* **Maximum Dose:** 200 mg/day. Use the lowest effective dose for the shortest duration.
## Pediatric Dosing
Safety and efficacy have not been established in children. Use is generally off-label or restricted to rheumatology specialists. Dosing varies by institutional protocol (often ~2–3 mg/kg/day divided TID/QID, not exceeding adult maximums).
## Dose Adjustments
* **Renal Impairment:** Use with extreme caution in CrCl <30 mL/min. Avoid in advanced renal disease.
* **Hepatic Impairment:** Use with caution. Monitor liver enzymes (ALT/AST). Dose reduction is recommended in mild-to-moderate impairment.
* **Geriatric:** Initiate at the lowest end of the dosing range; monitor for increased risk of GI bleeding and renal toxicity.
## Contraindications
* Known hypersensitivity to diclofenac or aspirin/other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active GI bleeding or peptic ulcer disease.
## Adverse Effects
* **Gastrointestinal:** Nausea, dyspepsia, ulceration, GI bleeding, perforation.
* **Cardiovascular:** Hypertension, fluid retention, edema, increased risk of MI/stroke.
* **Renal:** Acute kidney injury, interstitial nephritis, hyperkalemia.
* **Hepatic:** Elevated LFTs; rare but serious hepatotoxicity.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelets/SSRIs/SNRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Increased risk of renal impairment and decreased efficacy of antihypertensive therapy.
* **Lithium/Methotrexate:** Diclofenac may increase serum concentrations/toxicity of these agents.
## Monitoring
* Baseline and periodic CBC, serum creatinine, and electrolytes.
* Baseline and periodic LFTs.
* Monitor blood pressure periodically.
* Assess for occult GI bleeding (unexplained anemia).
## Clinical Pearls
* **Administration:** Take with food or milk to minimize GI upset.
* **Formulations:** Diclofenac sodium and potassium salts are not always interchangeable milligram-for-milligram; confirm specific product labeling.
* **Cardiovascular Risk:** All NSAIDs (except aspirin) carry a boxed warning for increased risk of serious cardiovascular thrombotic events.
* **GI Protection:** Consider adding a PPI or misoprostol if the patient is at high risk for GI complications.
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**Educational Disclaimer:** This information is for educational purposes only. Always verify dosing and contraindications against current clinical guidelines, manufacturer prescribing information, and local institutional protocols before prescribing or administering medication.
