For the use of a Registered Medical Practitioner, Hospital or Laboratory only.
1. Description
AddPhos contains 3.2 g of sodium acid phosphate granules per sachet. The sodium and potassium content in each sachet is 20.4 mmol and 3.1 mmol respectively. Available as granules providing Phosphorus 500 mg, equivalent to Phosphate 16.1 mmol per sachet.
2. Composition
Each sachet contains 3.2 g of Sodium Acid Phosphate Granules (Phosphorus 500 mg).
3. Dosage Form
Granules (sachet)
4. Pharmacology
Drug Class: Electrolyte replacement agent (oral phosphate supplement).
Active Ingredient: Sodium Acid Phosphate, providing Phosphorus 500 mg (16.1 mmol phosphate) per sachet.
Pharmacodynamics
Mechanism of Action
- Supplies phosphate ions to replace losses caused by malnutrition, refeeding, alcoholism, diabetic ketoacidosis, renal tubular losses, or use of phosphate-binding antacids and diuretics.
- Phosphate is the principal intracellular anion and is essential for ATP and 2,3-DPG formation, cell-membrane phospholipids, nucleic acids and acid–base buffering.
- Restoring serum phosphate supports normal skeletal and respiratory muscle function, myocardial contractility, red-cell oxygen delivery and bone mineralisation.
- In hypercalcaemia, oral phosphate binds calcium in the gut, reduces calcium absorption and promotes calcium deposition, lowering serum calcium.
- In calcium kidney stones, phosphate increases urinary pyrophosphate (a crystallisation inhibitor) and reduces urinary calcium excretion.
Phosphorous is one of the most abundant elements in the human body — nearly 85% is present in the skeleton, with a balance in soft tissues and extracellular fluid. Most phosphorous are complexed as phosphate which is the body’s major intercellular anion and an essential component of cell membrane phospholipids, DNA and RNA. It is also critical to most biochemical processes including ATP synthesis and metabolic and enzymatic pathways. Phosphorous, as phosphate, also assists in maintaining normal physiological pH balance.
Phosphorous balance is regulated by several hormones including Parathyroid Hormone (PTH), which controls the release of phosphate from bones and inhibits renal reabsorption. Serum phosphate levels are inversely proportional to serum calcium levels and their physiological requirements are the same.
Mechanism of Action: Oral administration of inorganic phosphates produce a fall in serum calcium in patients with hypercalcaemia. The sodium ions in AddPhos granules aid in the correction of the dehydration and sodium depletion, which is seen in hypercalcaemia. In cases of hypercalcaemia associated with impaired renal function and hypophosphataemia, the main effect of oral phosphate is to bind calcium in the gut and thus reduce calcium absorption.
Pharmacokinetics
Absorption
Approximately 60–70% of an oral phosphate dose is absorbed, mainly in the duodenum and jejunum, by passive paracellular diffusion and active vitamin D–dependent transport.
Distribution
About 85% of body phosphorus is in bone, about 14% is intracellular and less than 1% is in extracellular fluid. Normal adult serum phosphate is 2.5–4.5 mg/dL (0.8–1.45 mmol/L).
Protein Binding
About 10–15% of plasma phosphate is protein bound.
Metabolism
Phosphate is not metabolised; it enters the body phosphate pool.
Elimination
About 90% is excreted by the kidneys; 80–90% of filtered phosphate is reabsorbed in the proximal tubule under the control of PTH and FGF-23. The remainder is excreted in the faeces.
Half-life
Phosphate has no fixed pharmacokinetic half-life because serum levels are regulated by homeostatic mechanisms.
Onset of Action
Serum phosphate rises within hours of an oral dose; the time to full repletion depends on the size of the deficit and renal function.
Absorption & Distribution
Phosphates are mainly absorbed from the jejunum and duodenum by passive and active transport. Approximately two-thirds of ingested phosphate is absorbed from the gastrointestinal tract and most absorbed phosphate is filtered by the glomeruli and subsequently undergoes reabsorption. PTH and Vitamin D stimulate absorption of phosphate from the small intestine and its reabsorption from the proximal tubule.
Metabolism & Elimination
Virtually, all absorbed phosphates are excreted in the urine; the remainder being excreted in the faeces.
5. Indications
AddPhos Granules are used as an oral phosphate supplement in the treatment of the following conditions:
- Hypophosphataemia
- Hypercalcaemia
- Phosphate depletion
- Calcium based kidney stone
6. Contraindications
AddPhos Granules are contraindicated in patients with a known hypersensitivity to sodium phosphate monobasic or any of the components of the granules.
7. Precautions
Considerations should be given to the sodium and potassium content of AddPhos Granules before administration to patients suffering from conditions associated with significant electrolyte imbalance or impaired renal function. In cases where restricted sodium intake is indicated, e.g., in the treatment of congestive cardiac failure, hypertension, pre-eclamptic toxemia, etc., the sodium and potassium content of AddPhos Granules should be taken into consideration.
Soft tissue calcification and nephrocalcinosis have been reported in isolated cases following intravenous therapy with phosphate. This is thought to be a function of dosage and rapidity of phosphate administration. While such effects appear less likely to occur following treatment with oral phosphates, careful surveillance of patients is recommended. The effect of oral phosphate on serum phosphate is likely to be minimal, but close monitoring of serum levels is recommended.
Use in Pregnancy: The safety of AddPhos Granules in human pregnancy has not been formally studied.
Use in Lactation: The safety of AddPhos Granules in breastfeeding mothers and their infants has not been formally studied. However, both sodium and phosphate are found in human milk.
Use in the Elderly: As an excessive dosage has been reported to produce hypocalcaemia in isolated cases, particular care should be taken to ensure appropriate dosage in the elderly.
8. Drug Interactions
Interactions with other medicines: Concurrent administrations of AddPhos Granules with antacids containing agents such as aluminium hydroxide, calcium or magnesium salts, may result in the displacement of calcium from binding to oral phosphate and thus reducing the efficacy of this medication.
Parathyroid hormone (PTH) increases the urinary excretion of phosphate by blocking tubular reabsorption. The risk of ectopic calcification may be increased by concurrent use of calcium supplements. Vitamin D increases the gastrointestinal absorption of phosphates and therefore, increase the potential for Hyperphosphataemia.
Drugs which may lower phosphorus levels
- Antacids – Antacids with aluminium, calcium or magnesium can hamper phosphorus absorption in the digestive system.
- Anticonvulsants – Anticonvulsants such as phenobarbital and carbamazepine can lower levels of phosphorus in the body and create enzymes that hamper absorption.
- Bile Acid Sequestrants – Bile acid sequestrants used to lower cholesterol can prevent phosphorus being absorbed by the body.
- Corticosteroids – Corticosteroids such as prednisone or methylprednisolone can increase the excretion of phosphorus in urine.
- Insulin – Insulin in high doses may lower phosphorus absorption.
- ACE inhibitors (BP medication) – Benazepril, Captopril, Enalapril and Lisinopril may lower levels of phosphorus.
- Ciclosporin – It may reduce the phosphorus absorption in the body.
- Heparin (Blood thinning)
- Non-steroidal Anti-Inflammatory drugs (Ibuprofen)
- Cardiac Glycosides (Digoxin)
9. Adverse Effects
- Gastrointestinal: nausea, vomiting, abdominal discomfort and diarrhoea (dose-related; reduce the dose if they occur).
- Metabolic: hyperphosphataemia, hypocalcaemia, hypernatraemia, hyperkalaemia and dehydration, particularly in renal impairment.
- Soft-tissue calcification and nephrocalcinosis have been reported rarely.
10. Dosage & Administration
AddPhos Granules sachet should be emptied and dissolved in 2/3rd to 1 full glass of water. The dosage should be adjusted to suit the requirements of individual patients.
- Phosphate Depletion : Up to 3 g/d in 3 to 4 divided doses
- Hypophosphataemia : 2-3 g/d in 3 to 4 divided doses
- Hypercalcaemia : 1-2 g/d
- Calcium Based Kidney Stone : 1-2 g/d
Estimated Phosphorus may vary with respect to weight of the patient.
Hypophosphataemia (Acute decrease); Estimated Phosphorus = 0.25 mmol / kg
Phosphate Depletion (Chronic); Estimated Phosphorus = 0.5 mmol / kg
Dosage As Per Body Weight
| Body Weight | Doses |
| 60 kg | 15 mmol every 6 hours with meals – 1 sachet of AddPhos qid |
| 70 kg | 17.5 mmol every 6 hours with meals – 1 sachet of AddPhos qid |
| 100 kg | 25 mmol every 6 hours with meals – 1.5 sachet of AddPhos qid |
As per the guidelines, the phosphorus level will increase by an average of 1.2 mg/dL with a dose of 0.25 mmol/ kg.
11. Overdosage
Excessive dosage has been reported to produce hypocalcaemia in isolated cases. This has proved reversible when dosage has been adjusted.
12. Storage
Store in a dry place at a temperature not exceeding 30°C. Protect from light. Keep the medicine out of reach of children.
13. Presentation
3.2 grams granules in a sachet, 15 sachets in a Box.