Diclofenac Dosing for a 28-Year-Old Adult Weighing 35 kg
For this 28-year-old adult weighing 35 kg with pain, use standard adult dosing of diclofenac: 50 mg three times daily orally (maximum 150 mg/day) or 75 mg intramuscularly/intravenously every 12 hours (maximum 150 mg/day), as weight-based dosing is not required in adults regardless of low body weight. 1, 2
Rationale for Standard Adult Dosing
Adult dosing is not weight-adjusted for diclofenac. The FDA-approved dosing for pain management is 50 mg orally three times daily, with a maximum of 150 mg/day, regardless of patient weight. 2
No dosage adjustments are required for low body weight in adults. Clinical pharmacokinetic studies demonstrate that diclofenac dosing does not need modification based on body weight, age, or most disease states in adults. 3, 4
The 35 kg weight is below typical adult range but does not change dosing. While this patient is significantly underweight for an adult, guidelines and drug labels do not specify weight-based reductions for adults, unlike pediatric populations. 1, 2
Recommended Dosing Regimens
Oral Administration (Preferred for Outpatient)
- Initial dose: 50 mg three times daily with meals to minimize gastrointestinal effects. 2
- Alternative: 100 mg initial dose followed by 50 mg doses may provide better relief in some patients. 2
- Maximum daily dose: 150 mg/day regardless of route. 1, 2
Injectable Administration (IM or IV)
- Dose: 75 mg every 12 hours (intramuscular or intravenous). 1, 5
- Maximum daily dose: 150 mg/day (two 75 mg doses). 1, 5
- Intramuscular route is preferred over IV due to lower risk of dilution and dosing errors. 1
- IV administration should be reserved for severe cases or hospital settings with appropriate monitoring. 1
Critical Safety Considerations in This Underweight Patient
Enhanced Monitoring Required
Monitor for gastrointestinal adverse effects (abdominal pain, nausea, vomiting) more closely, as this patient's low body weight may increase vulnerability. 1, 5
Assess renal function before initiating therapy and monitor if treatment extends beyond 3-5 days, checking serum creatinine and electrolytes. 5
Evaluate for underlying conditions causing low body weight that might contraindicate NSAID use (malnutrition, chronic disease, eating disorders). 1
Absolute Contraindications
Avoid diclofenac completely if patient has: active peptic ulcer disease, severe heart failure, liver failure, or history of gastrointestinal bleeding. 1
Use extreme caution or avoid if patient has: history of peptic ulcer, significant alcohol use, concomitant anticoagulants, pre-existing cardiovascular disease, or compromised fluid status. 1
Duration Limits
Maximum treatment duration: 5 days for pain, 3 days for fever in outpatient settings without close monitoring. 6
If no response after trying two NSAIDs sequentially, switch to alternative analgesia (opioids or non-pharmacologic interventions) rather than continuing NSAID trials. 1
Common Pitfalls to Avoid
Do not reduce the dose based solely on low body weight in adults—this is not supported by pharmacokinetic data and may result in inadequate analgesia. 3, 4
Do not exceed 150 mg/day by any route, as higher doses significantly increase gastrointestinal and renal toxicity without additional benefit. 1, 5
Do not combine with anticoagulants without close monitoring, as bleeding risk increases 3-6 fold. 1
Do not use different formulations interchangeably (immediate-release vs. extended-release vs. enteric-coated), as they are not bioequivalent even at the same milligram strength. 2