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# Diclofenac
## Overview
Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) that acts by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Osteoarthritis
* Rheumatoid arthritis
* Ankylosing spondylitis
* Acute pain or primary dysmenorrhea (oral potassium salt preferred)
## Adult Dosing
* **Oral (Delayed-release/Enteric-coated):** 50 mg BID or TID, or 75 mg BID. Maximum: 150 mg/day.
* **Oral (Extended-release):** 100 mg daily. Maximum: 100 mg/day.
* **Oral (Potassium salt):** 50 mg TID. Maximum: 150 mg/day (for acute pain).
* **Topical (Gel 1%):** Apply 2-4 grams to affected area QID. Do not exceed 32g/day total across all joints.
## Pediatric Dosing
* **Juvenile Rheumatoid Arthritis (≥ 2 years):** 2–3 mg/kg/day divided into 2–3 doses. Maximum: 3 mg/kg/day or 150 mg/day.
* **Other indications:** Not systematically established; use requires specialist oversight and weight-based protocol.
## Dose Adjustments
* **Renal Impairment:** Avoid in severe renal impairment (CrCl < 30 mL/min). Use with caution in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution. Consider lower starting doses. Monitor transaminases (ALT/AST).
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of GI bleeds and renal toxicity.
## Contraindications
* Known hypersensitivity to diclofenac or aspirin.
* 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
* **Cardiovascular:** Hypertension, edema, increased risk of MI/stroke (boxed warning).
* **Gastrointestinal:** Dyspepsia, nausea, occult GI bleeding, ulceration, perforation.
* **Renal:** Acute kidney injury, fluid retention, hyperkalemia.
* **Hepatic:** Elevated liver enzymes to rare cases of fulminant hepatitis.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets (e.g., Warfarin, SSRIs):** Increased risk of bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Diminished antihypertensive effect and increased risk of renal impairment (the "triple whammy").
* **Lithium/Methotrexate:** Increases serum concentrations and toxicity risk.
* **Other NSAIDs:** Avoid combination due to additive toxicity without increased efficacy.
## Monitoring
* Baseline and periodic CBC, BMP (renal function, electrolytes).
* Monitor BP during initiation and titration.
* Liver function tests if long-term therapy is employed.
* Watch for signs of GI bleeding (melena, hematemesis).
## Clinical Pearls
* **Cardiovascular Risk:** All NSAIDs, including diclofenac, carry a boxed warning for increased risk of serious cardiovascular thrombotic events.
* **GI Protection:** Consider the addition of a proton pump inhibitor (PPI) or misoprostol in high-risk patients.
* **Enteric Coating:** Delayed-release formulations are not intended for rapid onset. Use potassium salt if rapid absorption is required.
* **Topical Safety:** While systemic absorption is lower via topical gel, systemic side effects can still occur; avoid application to open wounds or skin infections.
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**Educational Disclaimer:** This information is for educational purposes and does not substitute for professional medical judgment. Always verify current prescribing information, dosing protocols, and patient-specific contraindications via reliable clinical resources (e.g., Lexicomp, UpToDate, or local institutional guidelines) before prescribing or administering medication.
