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Phosphorus is an essential electrolyte critical for bone mineralization, cellular energy production, and acid-base balance. In pediatric patients, phosphorus deficiency (hypophosphatemia) can arise from prematurity, malnutrition, renal tubular disorders, or chronic antacid use. Oral phosphorus supplementation is often preferred in stable patients due to its safety profile and ease of administration. This article reviews the clinical uses, dosing, preparation, stability, and monitoring of oral phosphorus formulations, with a focus on practical guidance for pediatricians.
Clinical Uses
Oral phosphorus is indicated for:
- Symptomatic hypophosphatemia:
- anorexia, muscle weakness, and osteomalacia can occur in severe chronic depletion. Serious neuromuscular disturbances may occur, including progressive encephalopathy, seizures, coma, and death.
- Chronic conditions:
- X-linked hypophosphatemic rickets (XLH).
- Fanconi syndrome.
- Post-transplant hypophosphatemia.
- Nutritional supplementation:
- Preterm infants on prolonged parenteral nutrition.
- Malabsorption syndromes (e.g., Crohn’s disease).
Normal Phosphate Blood Level for Pediatrics:
| Age | Phosphate (mg/dL) |
| 0 – 14 d | 5.6–10.5 |
| 15 d – <1 y | 4.8–8.4 |
| 1 – <5 y | 4.3–6.8 |
| 5 – <13 y | 4.1–5.9 |
| 13 – <16 y Boy: | 3.5–6.2 |
| 13 – <16 y Girl: | 3.2–5.5 |
| 16 – <19 y | 2.9–5.0 |
Dosing Guidelines
Dosing is weight-based and adjusted to serum phosphate levels:
| Age Group | Dose Range | Frequency |
| Neonates | 0.5–1.5 mmol/kg/day | Divided q6–8h |
| Infants/Children | 1–3 mmol/kg/day | Divided q6–8h |
| Adolescents | 30–60 mmol/day | Divided q6h |
Notes:
- Start at the lower end for chronic supplementation.
- Monitor serum phosphate, calcium, and renal function every 3–7 days.
Formulations & Preparation
1. Compounding Oral Solutions:
- Common salts: Sodium phosphate (monobasic or dibasic) or potassium phosphate.
- Example recipe:
- Disodium phosphate (NaH₂PO₄): 27 g
- Phosphoric acid (85%): 13 mL
- Diluted to 200 mL with water → 1.9 mmol/mL.
- Joulie’s solution:
- While Joulie’s solution is used widely in the NHS, an exact formulation has yet to be agreed. The supervising pharmacist should take steps to validate and check the formulation to be prepared or procured.
2. Stability Considerations:
- Refrigeration: Stable for 7–14 days at 2–8°C.
- Incompatibilities: Avoid calcium-containing solutions (risk of precipitation).
Using the Pediatric Phosphate Calculator
The Phosphate Concentration Calculator aids in preparing accurate oral solutions when combining sodium phosphate salts and phosphoric acid.
Step-by-Step Guide:
- Select phosphate type: Choose disodium (Na₂HPO₄ – 141.96 g/mol) or monosodium (NaH₂PO₄ – 120 g/mol) phosphate.
- Input salt weight: Enter grams of sodium phosphate.
- Phosphoric acid (98 g/mol) details: Provide concentration (%) and volume (mL).
- Final volume: Specify total solution volume (mL).
Example Case:
A 5 kg infant requires 1 mmol/kg/day of phosphate. Using the calculator:
- Disodium phosphate: 27 g
- Phosphoric acid (85%): 13 mL
- Final volume: 200 mL → 1.9 mmol/mL.
- Dose: 5 mL daily provides 9.5 mmol (~2 mmol/kg).
- Dose: 1x5x1/1.9 ~ 2.5 ml/day
Oral phosphorus therapy is a cornerstone of managing hypophosphatemia in children. Safe administration requires attention to dosing, compounding accuracy, and monitoring. The Pediatric Phosphate Calculator streamlines preparation, reducing errors in custom formulations. Always individualize therapy based on laboratory trends and clinical response. If you need more assistance or have any question, you can consult us at Pedia Consult or start a thread at Pedia Ask.
Key Takeaway:
“In pediatrics, small dosing errors can have large consequences. Double-check calculations and use tools like the Phosphate Calculator to ensure precision.”
