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HypoPhosphatemia: diff dx

- Discussion:
- normal phosphate serum levels are 3 to 4.5 mg/dL in adults and 4 to 7.5 mg/dL in children (Boyd & Olin, 1984);
- hypophosphatemia occurs with serum P levels of < 0.8 mmol/L (2.5 mg/dL);- Differential Dx:
- rickets / osteomalacia:
- hypophosphatemia is the most common metabolic anomaly in rickets;
- hypophosphatemic vitamin D-resistant rickets:
- hyperparathyroidism
- ETOH
- diabetes mellitus
- hyperalimentation
- acidosis,
- alkalosis
- gout
- salicylate poisening
- steroids
- glucose and/or Insulin administration
- hypokalemia
- hypomagnesemia
- diuretics
- vitamin D defficiency
- phosphate binding antacids
- malabsorption;

- Clinical Manifestations:
- acute manifestations of phosphorous deficiency include central nervous system dysfunction (lethargy, altered mental status, focal  neurological findings), muscular weakness and rhabdomyolysis, hemolytic anemia, & defects in platlet and leukocyte function;
- metastatic calcification can occur if the calcium-phosphorus product exceeds 2.5 x 10(-6) mmol/L (5.8 mg/dL);
rickets, multiple sclerosis, and diabetic ketoacidosis;

- Dosing Information:
- severe hypophosphatemia may require 300 mg phosphorus IV in half-normal saline infused over 12 hours.
- K-phos neutral - phosphorus 250 mg, sodium 298 mg, potassium 45 mg;
- Neutra-phos - phosphorus 250 mg, sodium 164 mg, potassium 278 mg;
- Neutra-phos-k - phosphorus 250 mg, potassium 556 mg;
- Dietary supplement;
- recommended daily allowance of phosphorus is 1200 milligrams daily in males and females 11 to 18 years of age;
- allowance is 800 milligrams daily in males and females 19 years of age and older;
- 1-2 grams of oral phosphorus/day are effective in treating adult hypercalcemia;
- 1.5 g IV infused over 6 to 8 hours may be used in severe, life-threatening hypercalcemia.
- to treat hypophosphatemia, 1 to 3 g oral or rectal phosphorus may be given daily to adults; children should receive 1 to 2 mmol/kg/24 hours IV or 2 to 4 mmol/kg/24 hours PO