This information is intended for use by health professionals

1. Name of the medicinal product

Sterile Potassium Acid Phosphate Solution.

2. Qualitative and quantitative composition

Potassium Acid Phosphate 13.6% w/v.

3. Pharmaceutical form

Sterile Aqueous Solution - Injection.

4. Clinical particulars
4.1 Therapeutic indications

As a source of potassium ions and phosphate ions in electrolyte replacement therapy.

4.2 Posology and method of administration

The normal concentration of serum inorganic phosphate is 3 to 4.5mg (0.03 to 0.045mmol) per 100ml in adults and 4 to 7 mg (0.04 to 0.07mmol) per 100ml in children.

Before administration, the concentrated phosphate injection must be diluted and thoroughly mixed with a larger volume of fluid.

The dose and rate of administration must be individualised.

When used as an electrolyte replenisher, a dose of the equivalent of 10 to 15mmol (310mg to 465mg) of phosphorus a day is usually sufficient to maintain normal serum phosphate, although larger amounts may be required in hypermetabolic states.

The solution should be infused slowly to avoid phosphate intoxication.

Usual adult and adolescent dose

As an electrolyte replenisher

The equivalent of 10mmol (310mg) of phosphorus a day by intravenous infusion

Usual Paediatric use

As an electrolyte replenisher

The equivalent of 1.5 to 2 mmol (46.5 to 62mg) of phosphorus a day by intravenous infusion.

4.3 Contraindications

Hyperphosphataemia

Renal function impairment severe - less than 30% of normal

Urolithiasis

Risk - Benefit should be considered when the following medical problems exist

(reasons given when appropriate):

Conditions in which high phosphate concentrations may be encountered, such as

Hypoparathyroidism

Chronic Renal Disease.

Conditions in which low calcium concentrations may be encountered, such as:

Hypoparathyroidism

Osteomalacia

Acute Pancreatitis.

Chronic Renal disease.

Rickets

Sensitivity to Potassium or Phosphates.

Cardiac disease, particularly in digitalised patients.

Conditions in which high potassium concentrations may be encountered, such as:

Severe adrenal insufficiency - Addison's disease

Acute dehydration.

Severe renal insufficiency.

Extensive tissue breakdown, such as severe burns.

Myotonia congenita

4.4 Special warnings and precautions for use

The product must be diluted before use.

Electrocardiogram (may be required at regular intervals during intravenous therapy)

4.5 Interaction with other medicinal products and other forms of interaction

Interactions with other medications include Captopril, Potassium - Sparing Diuretics, Enalapril, Lisinopril, Adrenocorticoids, Glucocorticoids (especially those with significant mineralocorticoid activity), Mineralocorticoids, Corticotropin (ACTH), Anabolic Steroids or Androgens.

Interaction with potassium containing medications (concurrent use with potassium phosphate may result in hyperkalaemia; patient should have serum potassium concentration determinations at periodic intervals).

Interaction with Digitalis Glycosides

Use of potassium phosphate injection in digitalised patients with severe or complete heart block is not recommended because of possible hyperkalaemia.

Interaction with Diuretics or Thiazides

Concurrent use with phosphate may cause or worsen renal damage.

Interaction with Mexiletine

May lead to marked acidification of urine by monobasic potassium phosphate and potassium and sodium phosphates combination may accelerate excretion of Mexiletine.

Interaction with Quinidine

Concurrent use with potassium phosphate usually enhances effects of the Quinidine.

Interaction with Salicylates

Concurrent use with potassium and sodium phosphates combination or monobasic potassium phosphate may increase plasma concentrations of salicylates since salicylate excretion is decreased in acidified urine; addition of these phosphates to patients stabilised on a salicylate may lead to toxic salicylate concentrations.

4.6. Pregnancy and lactation

There has been no adequate and well controlled studies carried out in this area in either humans or animals.

It is not known if phosphates are excreted in breast milk. However problems in nursing infants have not been documented.

4.7 Effects on ability to drive and use machines

None stated

4.8 Undesirable effects

Undesirable effects include:

Fluid retention (swelling of feet or lower legs and weight gain).

Hyperkalemia (confusion, tiredness or weakness, irregular or slow heartbeat, numbness or tingling around lips, hands or feet, unexplained anxiety, weakness or heaviness of legs, shortness of breath or troubled breathing).

Hypernatremia (confusion, tiredness or weakness, convulsions, decrease in amount of urine or in frequency of urination, fast heartbeat, headache or dizziness, increased thirst).

Hyperphosphataemia.

Hypocalcemic tetany (muscle cramps, numbness, tingling, pain or weakness in hands or feet, shortness of breath or troubled breathing).

4.9 Overdose

May result in hyperkalaemia and hyperphosphataemia.

Recommended treatment consists of the following:-

Withholding administration of phosphates

Correcting deficient serum electrolyte concentrations (such as that of calcium)

5. Pharmacological properties
5.1 Pharmacodynamic properties

Potassium is the principle cation in intracellular fluid. It is involved with carbohydrate metabolism, glycogen storage and protein synthesis.

It is involved with transmembrane potential and profound effects on muscle.

Phosphorus has many important biochemical functions in the body and is involved in many significant metabolic and enzyme reactions in almost all organs and tissues.

5.2 Pharmacokinetic properties

The normal levels of potassium in intracellular fluid and plasma are 160mmol/l and 3.5 - 5.0mmol/l respectively.

The normal level of phosphate in plasma is 0.8 - 1.5mmol/l.

5.3 Preclinical safety data

No data available.

6. Pharmaceutical particulars
6.1 List of excipients

Disodium Edetate BP

Water for Injection BP

6.2 Incompatibilities

A precipitate may form when phosphates are added to a solution containing calcium or magnesium.

6.3 Shelf life

36 Months.

6.4 Special precautions for storage

None noted.

6.5 Nature and contents of container

Product is filled into clear colourless 10ml ampoules of Ph.Eur. type I glass.

Packed into cartons of 10 ampoules.

6.6 Special precautions for disposal and other handling

None

7. Marketing authorisation holder

Macarthys Laboratories Limited

T/A Martindale Pharmaceuticals

Bampton Road,

Harold Hill,

Romford,

RM3 8UG

8. Marketing authorisation number(s)

PL 01883 /0013

9. Date of first authorisation/renewal of the authorisation

First Authorisation:

19th January 1984

Renewal Date:

10th September 1998

10. Date of revision of the text

November 1999