Phosphate Dosing
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Patient's weight:
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Current phosphate level:
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Patient is:
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Phosphate supplementation
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Phosphate Summary:
Phosphorus: (hypophosphatemia):
-Oral: ~2 packets (16 mmol) Neutra-Phos qid (with meals and at
bedtime).
RDA: (1 packet qid = 1 gram phosphorus = 32 mmol)
Phosphates
Phosphate supplement: Oral: Elemental phosphorus 250 to 500 mg 4
times/day after meals and at bedtime.
P (MW=31). 250mg = 8.06 mmol. RDA (adults): 800-1200mg
phosphorus/day = ~26 - 38 mmol/day. (pregnant/lactating women:
1200mg/day). |
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Product |
P (mmol) |
Na+ meq |
K+ meq |
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Oral |
| Neutra-Phos®
(capsule /pkt) |
8 |
7.1 |
7.1 |
| Neutra-Phos K®
(capsule /pkt) |
8 |
0 |
14.25 |
| Skim milk per 8
oz (1 cup) |
8 |
3 |
5 |
| K-Phos ®
Neutral (tablet) |
8 |
13 |
1.1 |
| Fleet® Phospho
Soda (soln) /ml |
4.15 |
4.82 |
0 |
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IV |
| Potassium
Phosphate (ml) |
3 |
0 |
4.4 |
| Sodium Phosphate
(ml) |
3 |
4.0 |
0 |
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3 mmol = 93 mg phosphorus (MW
= 31) |
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K-hos ® Neutral Tablets: [ Each tablet contains approximately 250 mg of
phosphorus, 298 mg of sodium (13.0 mEq) and 45 mg of potassium (1.1 mEq).]
Dosage and administration:
Tablets should be taken with a full glass of water, with meals and at
bedtime. Adults: One or two tablets four times daily. Pediatric Patients
over 4 years of age: One tablet four times daily.
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K-PHOS® ORIGINAL (Sodium Free): Each tablet contains potassium acid
phosphate 500 mg [~ 114 mg (3.68 mmol) of phosphorus and 144 mg of K+ (
3.7 mEq)]. ACTIONS: highly effective urinary acidifier.
INDICATIONS: For use in patients with elevated urinary pH.
Helps keep calcium soluble and reduces odor and rash caused by
ammoniacal urine. Also, by acidifying the urine, it increases the
antibacterial activity of methenamine mandelate / hippurate.
DOSAGE:: Two tabs ( dissolved in 6-8 oz. of water) 4 times daily
with meals and at bedtime. |
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Neutra-Phos ®: (mix with at least 2.5 ounces
(75 ml) of water/juice).
Dosage: 1 pkt four times daily with meals and
at bedtime. Mild laxative effect possible.
[1 packet equivalent to
elemental phosphorus 250 mg (~8 mmol), sodium 164 mg (7.1 mEq), and
potassium 278 mg (7.1 mEq) per packet].
Dave's Tip: Remember that 1 pkt
qid = RDA (1000 mg Phosphorus).
Table below (oral therapy for hypophosphatemia) shows that ~2 pkt's qid for
treatment and 1 pkt for supplementation. [0.2 mmol x 70kg x 4 (e.g q6h)
= 56 mmol = ~14 mmol (2 pkts) qid] |
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NORMAL LEVELS: 2.4 - 4.5 mg/dl (0.8 - 1.5 mmol/L)
Causes: Decreased intake: malnutrition, malabsorption,
vitamin D deficiency, phosphate binders, alcoholism. Shifts from serum
into cells: respiratory alkalosis, refeeding, hyperalimentation, effects
of insulin/glucagon/androgens. Increased urinary secretion: renal
tubular defect, DKA.
Signs (generally seen only with total body depletion
and serum PO4 < 1 mg/dL): weakness, rhabdomyolysis, respiratory
compromise/failure, CHF, paresthesias, confusion, stupor, seizures,
coma, hemolysis, platelet dysfunction, metabolic acidosis.
Therapy: Determine Ca x PO4 product before
administering phosphorus: If the product is greater than 60 mg/dl,
there is a risk of calcium phosphate precipitation in the cornea, lung,
kidney, cardiac conduction system, and blood vessels.
Oral therapy: For
Phosphorus > 1 mg/dl (>0.3 mmol/L), oral therapy may be used.
1-2 tabs/pkts (8-16 mmol) TID-QID.
[0.2 mmol x 70kg x 4 (e.g q6h) = 56 mmol = ~14 mmol (2 pkts) qid]
Estimated Phosphorus
Requirements
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(0.2-0.3 mmol/kg q6h
= number of packets of Neutra-Phos®/24 hrs)
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Patient weight |
# pkts/24hr |
0.2 -0.3 mmol/24hr |
0.25 mmol/kg |
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60 kg |
6 - 9 |
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15 |
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70 |
7 - 10.5 |
56-84 (14-21 mmol
q6h) |
17.5 |
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80 |
8 - 12 |
64-96 (16-24 mmol
q6h) |
20 |
|
90 |
9 - 13.5 |
72-108 (18-27 mmol
q6h) |
22.5 |
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100 |
10 - 15 |
80-120 (20-30 mmol
q6h) |
25 |
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As a guideline,
the phosphorus level will increase by an average
of 1.2 mg/dl with a dose of 0.25mmol/kg.
Monitoring (IV): Phosphorus levels should be
drawn at the end of the infusion and should
always be drawn prior to any additional doses
administered. |
IV REPLACEMENT:
For Phosphorus < 1 mg/dl (< 0.3mmol/L).
Acute decreases in PO4: 0.25 mmol/kg IBW* (infuse over 4-6 hours)
Chronic depletion of PO4: 0.5 mmol/kg IBW* (infuse over 6 hours)
Renal insufficiency (CrCL <20ml/min): reduce dose by 50%.
Preparation
Floors: KPhos or NaPhos 15 mmol/250 ml
ICU's: KPhos or NaPhos 15 mmol/100ml NS/D5W over 2 hours centrally.
(This method of administration is NOT recommended if: total calcium is <
7.5 mg/dL or > 11 mg/dL (corrected for albumin**) phosphorus is > 2 mg/dL
OR significant renal dysfunction (Clcr < 10 ml/min).
Note: Phosphorus has historically been administered over 4 to 6 hours
due to the potential risk associated with high doses and rapid
administration (i.e., hypocalcemia, hypotension, metastatic
calcification, renal failure). However, most of this data comes from
cases of hypercalcemia treated with large doses of intravenous
phosphates in which phosphorus levels were typically normal. More
aggressive electrolyte replacement is not considered as risky. |
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References:
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| 1 |
Bollaert PE, Levy B, Nace L,
Laterre PF, Larcan A. Hemodynamic and metabolic effects of rapid
correction of hypophosphatemia in patients with septic shock. Chest
1995 Jun;107(6):1698-701 |
| 2 |
Charron T, Bernard F, Skrobik Y, Simoneau N, Gagnon N, Leblanc M. Intravenous phosphate in the intensive care unit: More aggressive repletion regimens for moderate and severe
hypophosphatemia. Intensive Care Med. 2003 Aug;29(8):1273-8. Epub 2003 Jul 05.
"In summary, ICU patients are prone to hypophosphatemia which can
lead to several physiological alterations in cell function. These
potential deleterious effects are reversed by phosphate
supplementation. Rapid correction of phosphate deficit, as
demonstrated here, appears safe. To prevent additional insult to
tissues from phosphate deficit and because phosphate infusion is
incompatible with many other medications we suggest infusing phosphate
in the following manner: 30 mmol potassium phosphate over 2 h or 45
mmol over 3 h in patients with a baseline serum potassium below 4.0
mmol/l and creatinine below 200 µmol/l. Slower protocols (i.e., 30
mmol potassium phosphate over 4 h or 45 mmol over 6 h) or sodium
phosphate (which is more expensive) are as efficacious and should be
favored if kalemia is a concern." |
| 3 |
Clark CL, Sacks GS, Dickerson
RN, Kudsk KA, Brown RO. Treatment of hypophosphatemia in patients
receiving specialized nutrition support using a graduated dosing
scheme: results from a prospective clinical trial. Crit Care Med 1995
Sep;23(9):1504-11. |
| 4 |
Kingston M, Al-Siba'i MB.
Treatment of severe hypophosphatemia. Crit Care Med 1985
Jan;13(1):16-8.
"A 4-h infusion of 310 to 465 mg (10 to 15 mMol) phosphorus given
to 28 of 31 consecutive seriously ill hypophosphatemic patients
increased the serum phosphorus level above 1.2 mg/dl in all but one
patient. There was no significant change in the mean serum calcium,
potassium or blood pressure, no patient deteriorated, and six patients
were stronger and more alert after the infusion. In seriously ill
patients we recommend a 4-h infusion of 15 mg/kg (0.5 mMol/kg)
phosphorus if the serum phosphorus is less than 0.5 mg/dl, or a
7.7-mg/kg (0.25 mMol/kg) infusion if the serum phosphorus is between
0.5 and 1.0 mg/dl." |
| 5 |
Lentz, RD, Brown, DM,
Kjellstrand, CM. Treatment of severe hypophosphatemia. Ann Intern Med 1978; 89:941. |
| 6 |
Miller DW, Slovis CM.
Hypophosphatemia in the emergency department therapeutics. Am J Emerg
Med 2000 Jul;18(4):457-61.
"Severe hypophosphatemia, as defined by a serum level below 1.0
mg/dL, may cause acute respiratory failure, myocardial depression, or
seizures."
Summary: Administering K2PO4 at a rate of 1 mL (3 mMol) per hour is almost always a very safe and appropriate treatment for
hypophosphatemia. |
| 7 |
Perreault MM, Ostrop NJ,
Tierney MG. Efficacy and safety of intravenous phosphate
replacement in critically ill patients. Ann Pharmacother 1997
Jun;31(6):683-8.
" CONCLUSIONS: The administration of potassium phosphate 15 mmol to critically ill patients with mild-to-moderate hypophosphatemia over 3 hours is both effective and safe. The administration of potassium phosphate 30 mmol to severely hypophosphatemic patients was safe but achieved normalization of serum phosphate in a minority of patients. Either a higher dose or the subsequent administration of more potassium phosphate may be required to normalize serum phosphate concentrations. Once normalization has occurred, there is a high likelihood of redevelopment of hypophosphatemia over the following 2 days and supplementation should be given accordingly."
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| 8 |
Rosen GH, Boullata
JI,
O'Rangers EA, Enow NB, Shin B. Department of Pharmacy,
University of Maryland Medical System, Baltimore, USA. Intravenous
phosphate repletion regimen for critically ill patients with moderate
hypophosphatemia. Crit Care Med 1995 Jul;23(7):1204-10 |
| 9 |
Schwartz A, Gurman G, Cohen G,
Gilutz H, Brill S, Schily M, Gurevitch B, Shoenfeld Y. Association
between hypophosphatemia and cardiac arrhythmias in the early stages
of sepsis. Eur J Intern Med 2002 Oct;13(7):434. |
| 10 |
Shiber JR, Mattu A. Serum phosphate abnormalities in the emergency department. J Emerg Med. 2002 Nov;23(4):395-400.
"Patients with severe or symptomatic hypophosphatemia should be treated with IV phosphate therapy (0.08-0.16 mg/kg over 6 h) and admitted for monitoring and subsequent serum electrolyte testing." |
| 11 |
Subramanian, R,
Khardori, R. Severe hypophosphatemia. Medicine 2000; 79:1. |
| 12 |
Wilson HK, Keuer SP, Lea AS,
Boyd AE 3rd, Eknoyan G. Phosphate therapy in diabetic ketoacidosis.
Arch Intern Med 1982 Mar;142(3):517-20 |
| 13 |
Zazzo JF, Troche G, Ruel P,
Maintenant J. High incidence of hypophosphatemia in surgical intensive
care patients: efficacy of phosphorus therapy on myocardial function.
ntensive Care Med 1995 Oct;21(10):826-31. |
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