Maximum Hydroxychloroquine Dose for 47 kg Patient
For a 47 kg patient, the maximum daily dose of hydroxychloroquine is 235 mg (calculated as 5.0 mg/kg actual body weight), which should not exceed 400 mg daily regardless of weight. 1
Weight-Based Dosing Calculation
The recommended maximum daily dose is strictly <5.0 mg/kg based on actual (real) body weight, not ideal body weight, as this minimizes retinal toxicity risk across all body habitus types. 1
For a 47 kg patient: 47 kg × 5.0 mg/kg = 235 mg maximum daily dose. 1
Since hydroxychloroquine tablets are available as 200 mg tablets, this patient should receive 200 mg daily to stay within safe dosing parameters. 2
Rationale for Real Weight Dosing
Previous recommendations using ideal body weight resulted in overdosing in thin individuals, as hydroxychloroquine stores primarily in melanotic tissue, liver, and kidney—not in fat or muscle. 1
Real weight-based dosing accounts for retinopathy risk evenly across different body types and prevents the systematic overdosing that occurred with ideal weight calculations. 1
Retinopathy Risk at Recommended Doses
Patients maintained at 5.0 mg/kg have <1% risk of retinopathy in the first 5 years and <2% risk up to 10 years of therapy. 1
Risk increases sharply to approximately 20% after 20 years of continuous use, even at recommended doses. 1
Daily doses exceeding 5 mg/kg significantly increase the incidence of retinopathy, which can be permanent and progress even after drug discontinuation. 2, 1
Practical Dosing Implementation
The 200 mg tablet cannot be divided or crushed per FDA labeling, so dose adjustments must use whole tablets. 2
For this 47 kg patient, 200 mg once daily is the appropriate dose, providing 4.26 mg/kg—well within safety guidelines. 2, 1
Alternatively, intermediate dosing can be achieved by eliminating tablets on certain days of the week, as blood levels stabilize over many weeks and variable dosing averages out over time. 1
Critical Monitoring Requirements
Baseline ophthalmologic examination is required before starting therapy, followed by annual screening after 5 years of use. 1, 3
Closer monitoring should be considered if cumulative dose exceeds 1000 g, if renal dysfunction is present, or if any retinopathy risk factors exist. 4, 3
The goal is to detect toxicity at the earliest stage to minimize visual loss, as no treatment exists for hydroxychloroquine retinopathy once it develops. 3, 1
Common Pitfall to Avoid
- Do not calculate dose based on ideal body weight—this outdated approach systematically overdoses patients, particularly those who are thin, increasing their retinopathy risk unnecessarily. 1