Phosphates, Phosphorus : Dosing

by MedlinePlus

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Sources of Phosphorus/Phosphates

Food sources: Phosphorus is found in most foods. Particularly rich sources include dairy products, meat, and fish. Phosphorus present in seeds, nuts, or grains (cereals) may be less well absorbed or digested compared to other sources, and is therefore about 50% less bioavailable. The average daily dietary intake of phosphorus by U.S. adults is not entirely clear, and has been estimated as being approximately 1.5 grams in men and 1.0 grams in women. Cola drinks contain significant amounts of phosphate, and excessive intake can result in hyperphosphatemia and hypocalcemia.

Phosphorus in specific foods (approximate): Almonds (1 ounce contains 139mg); beef (3 ounces contains 173mg); enriched white bread (1 slice contains 24mg); whole wheat bread (1 slice contains 64mg); carbonated cola drinks (12 ounces contains 44mg); part-skim mozzarella cheese (1 ounce contains 131mg); chicken (3 ounces contains 155mg); egg (1 large cooked egg contains 104mg); halibut fish (3 ounces contains 242mg); salmon fish (3 ounces contains 252mg); lentils (1/2 cup contains 356mg); skim milk (8 ounces contains 247mg); peanuts (1 ounce contains 101mg); turkey (3 ounces contains 173mg); plain nonfat yogurt (8 ounces contains 383mg).

Intravenous: Injectable potassium phosphate is an FDA approved prescription product to be administered by a licensed healthcare professional.

Adults (18 years and older)

Recommended daily intake: The National Academy of Sciences has recommended 700mg of phosphorus per day in adults ages 18 years and older, including pregnant or breastfeeding women.

Tolerable Upper Intake Level (UL): For adults ages 19-70 years-old the UL is 4 grams/day; for adults 70 years and older the UL is 3 grams/day. The recommended UL in pregnant women is 3.5 grams/day, and in breastfeeding women is 4 grams/day. Phosphate salts should not be administered to patients with hyperphosphatemia, and should be used cautiously in those with impaired kidney function.

Hypercalcemia: The equivalent of 1-2 grams of oral phosphorus/day in divided doses as a phosphate salt (sodium phosphate or potassium phosphate) may be used in the management of adult hypercalcemia. In severe, life-threatening hypercalcemia, 1.5 grams intravenously infused over 6-8 hours may be used under strict medical supervision. Serum electrolyte levels should be monitored.

Hypophosphatemia: The equivalent of 1-3 grams of oral or rectal phosphorus/day may be administered to adults as a phosphate salt (sodium phosphate or potassium phosphate). Severe hypophosphatemia may require 300mg of phosphorus intravenously in half-normal saline infused over 12 hours (consider repeating until serum phosphorus concentrations exceed 1 mg/deciliter). Serum electrolyte levels should be monitored.

Saline laxative/Fleet Phospho-soda: 4-8 grams of sodium phosphate dissolved in water has been used as a saline laxative (should be taken with plenty of water). For bowel preparation before diagnostic tests, various oral and rectal preparations have been used which include dibasic sodium phosphate and monobasic sodium phosphate. These should be used as directed. For example, Fleet Phospho-soda should be prescribed by volume. Excessive dosing may occur if prescribed "by the bottle" because Fleet Phospho-soda is available in bottles of 1.5 ounces and 3.0 ounces. The timing of doses is usually determined by the clinician. The manufacturer has recommended 2 doses of 45mL each as a bowel preparation for colonoscopy, surgery, and radiology procedures. Each 5mL contains 2.4 grams of monobasic sodium phosphate monohydrate and 0.9 grams of dibasic sodium phosphate heptahydrate. The elemental and electrolytic content is 12.45 mEq/mL of phosphate, 4.82 mEq/mL of sodium, and 4.15 mmol/mL of phosphorus. Works best when taken on an empty stomach, and should be taken at least 30 minutes before breakfast or at bedtime. Depending on the dosage, this product usually produces a bowel movement in 30 minutes to 6 hours. Another recommendation for adults and children over 12 years-old is 20mL of Phospho-soda (containing 3.6 grams of sodium phosphate and 9.6 of grams sodium biphosphate) diluted in half a glass of cold water (after drinking the diluted Phospho-soda, drink 1 glass of cold water).

Fleet Enema: Fleet Enema (118 milliliters) can be used as a laxative when administered rectally. It should be administered as a single daily dose. Laxatives should not generally be used for more than 1 week. The rectal administration technique can involve the patient lying on his or her left side with the left knee bent and the right leg drawn up; the cover should be removed from the applicator tip of the bottle and the applicator tip should be gently inserted into the rectum with the tip pointing towards the navel. Insertion of the tip may be easier by bearing down as if having a bowel movement. Once the tip is inserted, squeeze the bottle until nearly all the liquid is expelled, but it should not be forced as there is a risk of perforation of the rectum. Results are generally seen in within 5 minutes.

Calcium oxalate kidney stones: Potassium and sodium phosphate salts providing 1200-1500 mg of elemental phosphate have been used in four divided daily doses, with water at meals.Caution: should not be used when stones are composed of magnesium-ammonium-phosphate or calcium phosphate, because the rate of stone formation may actually increase.

TPN/Hyperalimentation: To prevent hypophosphatemia in patients receiving intravenous feeding (hyperalimentation), 12-15 mmol/liter has been added to hyperalimentation fluids. Should be calculated and coordinated by a licensed nutritionist.

Refeeding syndrome: When serum phosphate falls below 0.5 mmol/liter during refeeding, intravenous phosphate 50 mmol (sodium 81 mmol, potassium 9.5 mmol) over 24 hours can be considered. Phosphate blood levels should be closely followed. Additional infusions of phosphate should be given if serum phosphate falls again below 0.5 mmol/liter.

Children (younger than 18 years)

Recommended Daily Intake (National Academy of Sciences; Food and Nutrition Board): The recommend adequate intake in infants 0-6 months-old is 100mg/day (additional phosphorus may be added to infant formulas); the recommended adequate intake in infants 7-12 months old is 275mg/day; the recommended daily intake in children ages 1-3 years-old is 460mg/day; the recommended daily intake in children ages 4-8 years-old is 500mg/day; the recommended daily intake in children ages 9-18 years-old is 1,250mg/day (including pregnant or breastfeeding females).

Hypophosphatemia: Children may receive 0.5 to 2 mmol/kg/24-hours intravenously, or 2 to 4 mmol/kg/24-hours orally. Severe hypophosphatemia may require higher doses under strict medical supervision.

Hyperalimentation: A recommended dose of phosphorus in infants receiving hyperalimentation is 0.5 to 2 mmol/kg/day. Should be calculated and coordinated by a licensed nutritionist.

Fleet Phospho-soda: Children 5 to 10 years-old may receive 5mL and should not exceed 10mL in a 24-hour period. Children between 10 to 12 years-old may receive 10mL and should not exceed 20 mL in a 24-hour period. Children over 12-years-old may receive a dose of 20mL and should not exceed 45mL in a 24-hour period. Do not administer to children under 5 years of age. Depending on the dosage, this product is expected to produce a bowel movement in 30 minutes to 6 hours.

Fleet Enema: Children under 12 years of age should not receive an adult size Fleet enema. Children 2 to 12 years of age may receive a Fleet Ready-To-Use Enema for children in a single daily dose (2 fluid ounces). Laxatives should not generally be used for more than 1 week.

Tolerable Upper Intake Level (UL): The UL for infants aged 0-12 months-old is not clearly established and the source of intake should be from food and formula only; for children 1-8 years-old the UL is 3 grams/day; for children 9-18 years-old the UL is 4 grams/day.

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