Relief of the pain of osteoarthritis of joints amenable to topical treatment (e.g., knees, hands).
Pharmacology:
Diclofenac gel is a topical non-steroidal anti-inflammatory drug (NSAID) that demonstrates an anti-inflammatory effect useful to treat the pain and swelling caused by medical conditions such as arthritis. Diclofenac has also been shown to have antinociceptive and antipyretic effects.
Diclofenac inhibits the enzyme, cyclooxygenase (COX), an early component of the arachidonic acid (AA) cascade. The AA cascade is a signaling pathway associated with the body’s inflammatory response. COX inhibition results in the lowering of AA cascade components such as prostaglandins, thromboxanes and prostacylin. It is not completely understood how reduced synthesis of these components results in therapeutic efficacy.
Clinical trials:
Two clinical trials were conducted to assess the efficacy of diclofenac gel in patients with osteoarthritis. In the first randomized, double-blind, placebo-controlled trial of 246 patients with osteoarthritis of the knee, 127 patients were administered diclofenac gel at a dose of 4g, 4 times daily, on 1 knee (16g per day). Pain was assessed by Week 12 using the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) Pain Subindex. On a scale of 0 (best response to pain) to 100 (worst response to pain), the WOMAC Pain Subindex was lower in the diclofenac gel group (mean: 28) than the placebo group (mean: 37).
In the second randomized, double-blind, placebo-controlled trial of 385 patients with osteoarthritis of the hand, 198 patients were administered diclofenac gel at a dose of 2g per hand, 4 times daily, on both hands (16g per day). The patients assessed their pain intensity in the target hand at Weeks 4 and 6. At both times, on a visual analog scale from 0 (best response to pain) to 100 (worst response to pain), the pain intensity assessment was lower in the diclofenac gel group (week 4: 43; week 6: 40) than the placebo group (week 4: 50; week 6: 47).
Adults:
Use dosing card to apply gel. Lower extremities (eg, knees, ankles, feet): Apply 4g to the affected area 4 times daily; max: 16g/day. Upper extremities (eg, elbows, wrists, hands): Apply 2g to the affected area 4 times daily; max: 8g/day. Total max dose over all affected joints: 32g/day. Do not wash treated hands for at least 1hr after application. Wait at least 10 minutes after application before getting dressed. Use on spine, hip, or shoulder has not been evaluated.
Children:
Not recommended.
Contraindications:
Aspirin allergy. Late pregnancy. Coronary artery bypass graft surgery.
Precautions:
Advanced renal disease: not recommended. Do not apply to open wounds, infections, inflammations, exfoliative dermatitis. Avoid eyes, mucous membranes, external heat and/or occlusive dressings, sunlight. Peptic ulcer. GI bleed. Asthma. CHF. Edema. Hypertension; monitor BP. Monitor blood, hepatic, renal function in long-term use; discontinue if toxicity develops. Elderly. Pregnancy (Cat.C). Nursing mothers: not recommended.
Interactions:
Avoid concomitant topical products and medications (eg, sunscreens, cosmetics, lotions, moisturizers, insect repellents). Increased risk of GI effects with aspirin, oral NSAIDs, corticosteroids, anticoagulants, alcohol, smoking. May antagonize diuretics, ACE-Inhibitors. Monitor for toxicity with lithium, methotrexate, cyclosporine.
Adverse reactions:
Application site reactions (dermatitis, pruritus, erythema, paresthesia, dryness, vesicles, irritation); GI bleed/ulceration, edema, rash (may be serious; eg, exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis), anaphylactoid reactions. See literature re: risk of cardiovascular events.