What is the recommended dosage of diclofenac (Nonsteroidal Anti-Inflammatory Drug (NSAID)) for an adult patient with pain or inflammation, considering factors such as age, weight, medical history, and potential contraindications like gastrointestinal issues or Impaired Renal Function?

Diclofenac Dosage Recommendations

Standard Oral Dosing

For acute pain or primary dysmenorrhea, start with diclofenac 50 mg three times daily, with an option to use an initial loading dose of 100 mg followed by 50 mg doses for better relief. 1

Indication-Specific Dosing:

• Acute pain/dysmenorrhea: 50 mg three times daily (total 150 mg/day), or 100 mg initial dose followed by 50 mg doses 1
• Osteoarthritis: 100-150 mg/day in divided doses (50 mg twice or three times daily) 1
• Rheumatoid arthritis: 150-200 mg/day in divided doses (50 mg three to four times daily) 1
• Maximum daily dose: 200 mg/day for oral formulations 1, 2

Injectable Diclofenac Dosing

For injectable diclofenac, use 75 mg intramuscularly as the preferred route, with a maximum daily dose of 150 mg (75 mg every 12 hours). 3

Injectable Administration Guidelines:

• Standard IM dose: 75 mg per injection 3
• Minimum interval between doses: 12 hours 3
• Maximum daily dose (IM or IV): 150 mg total 3
• Preferred route: Intramuscular over intravenous to avoid dilution errors and dosing complications 3
• Acute renal colic: Single 75 mg IM dose as first-line treatment 3
• Acute crystal-induced arthritis: 150 mg daily for 3 days, then 75 mg daily for 3 additional days 3

Critical Dosing Considerations by Patient Risk Profile

Age-Related Adjustments:

Patients ≥65 years require gastroprotection with a proton pump inhibitor (PPI) when using diclofenac, regardless of GI history. 4

• Age <65, no GI history, no aspirin: Diclofenac alone is appropriate 4
• Age ≥65 OR previous GI event: Diclofenac + PPI is mandatory 4
• Age ≥65 with previous complicated GI event + aspirin/steroids/warfarin: Diclofenac + PPI is appropriate 4

Gastrointestinal Risk Stratification:

Avoid diclofenac completely in patients with active peptic ulcer disease; use diclofenac + PPI in those with prior GI bleeding. 4, 3

• No previous GI event, age <65, no aspirin: Diclofenac alone 4
• Previous GI event, not on aspirin: Diclofenac + PPI 4
• On aspirin, no previous GI event: Consider COX-2 inhibitor instead 4
• Previous GI event + aspirin: Diclofenac + PPI or COX-2 + PPI 4

Renal Impairment:

Reduce dose or discontinue diclofenac if creatinine clearance <10 mL/min; stop immediately if BUN or creatinine doubles during treatment. 3

• Monitor BUN and creatinine at baseline and every 3 months during chronic therapy 3
• Use extreme caution with compromised fluid status or concurrent nephrotoxic drugs 3

Hepatic Dysfunction:

Use diclofenac with caution in hepatic impairment; discontinue if liver function tests rise to 3× upper limit of normal. 3

• Monitor liver function studies at baseline and every 3 months 3
• No routine dose adjustment required for mild-moderate hepatic disease 5, 6

Cardiovascular Disease:

Diclofenac carries increased cardiovascular risk; avoid in patients with pre-existing heart disease or use with extreme caution. 4, 3

• Higher cardiovascular risk compared to other NSAIDs 4
• Contraindicated in severe heart failure 3

Anticoagulant Interactions

Never combine diclofenac with anticoagulants without gastroprotection and close monitoring, as bleeding risk increases 3-6 fold. 3

Anticoagulant Management:

• On warfarin/anticoagulants alone: Diclofenac + PPI is appropriate 4
• On aspirin + warfarin: Diclofenac + PPI is appropriate 4
• Bleeding risk: Increases 3-6 fold with concomitant anticoagulation 3
• Monitor INR closely as it may increase up to 15% 3

Monitoring Requirements for Chronic Therapy

Monitor blood pressure, BUN, creatinine, liver function tests, CBC, and fecal occult blood at baseline and every 3 months during chronic NSAID therapy. 3

Discontinuation Criteria:

• BUN or creatinine doubles 3
• Liver function tests ≥3× upper limit of normal 3
• Development or worsening of hypertension 3
• Any GI bleeding 3

Treatment Duration and Alternative Strategies

If two different NSAIDs (including diclofenac) fail sequentially, switch to opioid analgesics or non-pharmacologic interventions rather than trialing additional NSAIDs. 3

• Initial trial: 2-4 weeks at maximum tolerated dose 7
• Consider tapering after 12 weeks of sustained response 7
• Alternative approaches: Opioids, nerve blocks, or topical NSAIDs for localized pain 3, 7

Common Pitfalls to Avoid

• Do not exceed 150 mg/day for injectable diclofenac (stricter limit than ketorolac) 3
• Different formulations are not bioequivalent even at same milligram strength (enteric-coated vs immediate-release vs extended-release) 1
• Do not combine multiple NSAIDs as patients often do this inadvertently, increasing adverse effects 7
• Always administer with food to minimize GI effects 2
• Avoid in third trimester of pregnancy (standard NSAID precaution) 4