PURECAL CHEWABLE TABLETS

Indications

• Phosphorus deficiency
• Bone health maintenance
• Nutritional supplementation
• Metabolic bone diseases

Dosage

Children: Refer to the BNF for Children for specific dosing information.

Adults: Refer to the BNF for specific dosing information.

Mechanism of action

Phosphorus decreases the absorption of intercellular calcified cartilage matrix by osteoclasts in the metaphyseal region of growing bones. This results in the formation of 'phosphorus bands' of increased bone density and thickness. Additionally, exposure to white phosphorus impairs protein synthesis by damaging the rough and smooth endoplasmic reticulum, leading to an accumulation of triglycerides in the liver and resulting in hepatic steatosis and fibrosis.

Pharmacodynamics

Phosphorus is vital for the formation of hydroxyapatite in bone, which is necessary for maintaining bone density and strength. It also plays a significant role in energy transfer through ATP and in cellular signaling pathways. The balance of phosphorus in the body is tightly regulated, as both deficiency and excess can lead to serious health issues, including bone disorders and metabolic dysfunctions.

Pharmacokinetics

Phosphorus is absorbed primarily in the intestines, with bioavailability influenced by dietary factors. It is distributed throughout the body and is predominantly found in bones and teeth. Phosphorus is excreted mainly via the kidneys, with regulation occurring through various hormonal mechanisms, including parathyroid hormone and calcitriol. The half-life can vary depending on dietary intake and individual metabolism.

Pregnancy

Phosphorus is generally regarded as safe during pregnancy when consumed in appropriate dietary amounts. However, excessive phosphorus intake should be avoided as it may lead to complications.

Breast-feeding

Phosphorus is excreted in breast milk, but it is essential for the health of both the mother and the infant. Supplementation should be considered carefully.

Storage

Store in a tightly closed container, in a cool, dry place away from direct sunlight.

Mechanism of action

Phosphorus apparently decreases the absorption of intercellular calcified cartilage matrix by osteoclasts, in the metaphyseal region of growing bones. Administration of phosphorus to growing animals or children produces "phosphorus bands" of increased bone density and thickness that are visible grossly or from radiograms. The "phosphorus bands" are observed in the metaphyseal region of growing bones, and represent areas of decreased absorption of the calcified cartilage matrix. Exposure to white phosphorus has been shown to damage the rough endoplasmic reticulum and cause a disaggregation of polyribosomes. This damage results in impairment of protein synthesis, in particular, a decrease in the synthesis of the apolipoprotein portion of very low density lipoproteins (VLDL), which are required for the transport of triglycerides. A significant decrease in protein synthesis has been detected as early as 3 hours after oral exposure. The smooth endoplasmic reticulum is also involved in the formation of the VLDLs, and damage to the smooth endoplasmic reticulum also impairs the formation of VLDLs. The net result of these ultrastructural changes is an accumulation of triglycerides in the liver. This results in steatosis and fibrosis, which is one of the mechanisms involved in the hepatotoxicity of white phosphorus. The mechanism behind the damage to the endoplasmic reticulum is not known; also, it is not known whether white phosphorus itself or a metabolite of white phosphorus is the damaging agent. In addition to these damages, white phosphorus or a metabolite causes damage to the mitochondria and nuclei in the livers of animals orally exposed to white phosphorus. The damage to the mitochondria may impair the cell's ability to produce ATP, thus resulting in necrosis of the cell. Fatty infiltration and/or cellular damage has also been observed in the kidney, brain, and heart. It is possible that white phosphorus (or a metabolite) also impairs the ability of cells in these organs to produce ATP. The mitochondrial damage may also inhibit fatty acid oxidation (also contributing to the decreased availability of ATP) which could result in an accumulation of fat in the organs.