APCAL FORTE TABLETS

Indications

• Primary prevention of vitamin D deficiency
• Treatment of vitamin D deficiency
• Renal osteodystrophy
• Established postmenopausal osteoporosis

Dosage

Adults: For the primary prevention of vitamin D deficiency: 400 units daily. For treatment of vitamin D deficiency: loading dose of 50

Mechanism of action

Colecalciferol is converted in the liver to 25-hydroxyvitamin D and subsequently in the kidneys to 1,25-dihydroxyvitamin D, its active form. These metabolites enhance the intestinal absorption of calcium and phosphorus, increase serum calcium and phosphate levels, and mobilize these minerals from bone. The synthesis of active metabolites requires 10 to 24 hours after administration, and the regulation of this metabolism is influenced by parathyroid hormone.

Pharmacodynamics

The pharmacological effects of colecalciferol are primarily mediated through its active metabolites, which promote the absorption of calcium and phosphate in the gastrointestinal tract, enhance renal reabsorption of calcium, and mobilize calcium from bones. This results in increased serum calcium levels, which are essential for various physiological functions, including bone mineralization. The action of colecalciferol is closely tied to parathyroid hormone levels, which regulate calcium homeostasis.

Pharmacokinetics

Colecalciferol is well absorbed from the gastrointestinal tract, particularly when taken with food. Its bioavailability can be affected by factors such as fat intake and gastrointestinal health. After absorption, colecalciferol is transported in the bloodstream, primarily bound to vitamin D-binding protein. Its distribution is widespread, and it is stored in adipose tissues. The half-life of colecalciferol is approximately 19 to 25 hours, but this can vary based on individual factors such as body fat and metabolic health.

Adverse effects

• Urinary tract infection
• Abdominal pain
• Dehydration
• Drowsiness
• Fever
• Growth retardation
• Muscle weakness
• Paralytic ileus
• Polydipsia
• Psychiatric disorders
• Sensory disorders
• Thirst
• Urinary disorders

Precautions

• Monitor plasma-calcium, phosphate, and creatinine concentrations regularly, particularly during dose titration.
• In patients with renal impairment, avoid unless advised by the manufacturer.
• Monitor calcium levels closely during treatment, especially if doses are adjusted.

Pregnancy

Colecalciferol can be used during pregnancy, but doses should be evaluated carefully to avoid excess vitamin D.

Breast-feeding

Colecalciferol is considered safe during breastfeeding, but supplementation should be monitored.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Capsules
• Tablets
• Oral solution
• Oral suspension

Indications

• Vitamin C deficiency
• Scurvy
• As an adjunct in the treatment of iron deficiency anemia
• Support for immune function
• Antioxidant therapy

Dosage

Adults: Refer to the BNF for specific

Mechanism of action

Ascorbic acid functions primarily as a reducing agent, donating electrons to various biochemical reactions. It is involved in the hydroxylation of proline and lysine residues in collagen synthesis, which is essential for maintaining connective tissue integrity. As an antioxidant, it also helps to regenerate other antioxidants, such as vitamin E, thereby protecting cells from oxidative damage. Furthermore, it enhances the absorption of non-heme iron from the gastrointestinal tract, promoting better iron utilization in the body.

Pharmacodynamics

Ascorbic acid is crucial for metabolic processes, including the synthesis of collagen and certain neurotransmitters. Its antioxidant properties help mitigate oxidative stress, which can lead to cellular damage and various diseases. The vitamin's role in iron absorption is particularly significant in preventing iron-deficiency anemia. The therapeutic effects of ascorbic acid are dose-dependent, with higher doses often resulting in more pronounced antioxidant effects.

Pharmacokinetics

Ascorbic acid is readily absorbed in the small intestine, with peak plasma concentrations occurring within 2 to 4 hours after oral administration. The bioavailability of ascorbic acid decreases at higher doses due to saturation of the transport mechanisms. It is distributed throughout bodily fluids and tissues, with highest concentrations found in the adrenal glands, pituitary gland, and leukocytes. The elimination half-life varies, typically ranging from 8 to 40 days, depending on the dose and the individual's renal function. Ascorbic acid is excreted primarily through the kidneys, with renal clearance being influenced by plasma concentration and renal health.

Interactions

• ascorbic acid + iron chelators: Unknown (increases risk of cardiovascular adverse effects)
• ascorbic acid + deferiprone: Unknown (increases risk of cardiovascular adverse effects)
• ascorbic acid + desferrioxamine: Unknown (increases risk of cardiovascular adverse effects)

Pregnancy

Ascorbic acid is generally considered safe during pregnancy but should be used with caution and only when necessary.

Breast-feeding

Ascorbic acid is excreted in breast milk and is generally considered safe during breastfeeding.

Storage

Store at room temperature, away from light and moisture.

Indications

• Malabsorption syndromes
• Crohn's disease
• Cystic fibrosis
• Short bowel syndrome
• Severe food allergies
• Inability to meet nutritional needs through standard diets

Dosage

Children: Refer to specific formulations for dosing, as paediatric dosages depend on the product and the child's nutritional needs.

Adults: Refer to specific formulations for dosing, as adult dosages vary based on the product used and the patient's nutritional requirements.

Mechanism of action

Elemental formulations provide nutrients in their simplest forms, which are readily absorbed in the small intestine. This bypasses complex digestive processes, making them suitable for individuals with compromised digestion or absorption capabilities. The nutrients in these formulations include amino acids, simple carbohydrates, and fatty acids, which can be directly utilized by the body's metabolic pathways.

Pharmacodynamics

Elemental formulations help restore nutritional balance by supplying essential macronutrients and micronutrients needed for metabolic processes. They support growth, maintain energy levels, and promote healing in patients with malabsorption or increased nutritional needs. The bioavailability of nutrients in elemental forms is typically high, allowing for efficient uptake and utilization by the body.

Pharmacokinetics

Following administration, elemental nutrients are absorbed in the gastrointestinal tract, primarily in the jejunum and ileum. The rate of absorption can vary based on the specific formulation and the individual's gastrointestinal health. Once absorbed, these nutrients enter systemic circulation and are transported to various tissues for utilization in metabolic processes. The elimination of unabsorbed nutrients occurs primarily through feces.

Adverse effects

• Nausea
• Vomiting
• Diarrhea
• Constipation
• Stomach cramps
• Dark stools
• Metallic taste
• Allergic reactions

Precautions

• Use with caution in patients with a history of gastrointestinal disorders.
• Monitor for signs of iron overload in patients receiving multiple iron products.
• Assess for the need for supplementation in patients with conditions causing malabsorption.

Pregnancy

Iron is essential during pregnancy, but supplementation should be guided by clinical need and under healthcare supervision.

Breast-feeding

Iron is excreted in breast milk; supplementation may be necessary depending on maternal iron status.

Storage

Store in a cool, dry place, away from direct sunlight and moisture. Keep out of reach of children.

Formulations

• Oral tablets
• Liquid formulations
• Injectable solutions

Dosage

Children: Refer to specific guidelines for pediatric dosing; consult the BNF for Children for accurate dosage information.

Adults: Refer to specific guidelines for use; dosage may vary based on the context of use.

Mechanism of action

Hydroxide ions act primarily as bases, neutralizing acids to form water and salts. They participate in various biochemical pathways, including selenium metabolism and the degradation of reactive oxygen species. Hydroxide can influence enzyme activity and stability by altering the pH of the environment, thereby affecting metabolic reactions.

Pharmacodynamics

Hydroxide ions can impact biological processes by changing the local pH, which influences enzyme activity, ion transport, and the solubility of other compounds. Their ability to neutralize acids can help regulate physiological pH, contributing to homeostasis in living organisms.

Pharmacokinetics

As an inorganic ion, hydroxide does not undergo traditional pharmacokinetic processes like absorption, distribution, metabolism, or excretion. Instead, it is rapidly equilibrated in biological fluids and participates in acid-base reactions, having immediate effects on the local environment.

Pregnancy

There is limited information regarding the use of hydroxide during pregnancy. Consult a healthcare professional for advice.

Breast-feeding

Limited data is available on the excretion of hydroxide in breast milk. Consult a healthcare professional before use.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Mechanism of action

Most individuals naturally generate adequate amounts of vitamin D through ordinary dietary intake of vitamin D (in some foods like eggs, fish, and cheese) and natural photochemical conversion of the vitamin D3 precursor 7-dehydrocholesterol in the skin via exposure to sunlight. Conversely, vitamin D deficiency can often occur from a combination of insufficient exposure to sunlight, inadequate dietary intake of vitamin D, genetic defects with endogenous vitamin D receptor, or even severe liver or kidney disease. Such deficiency is known for resulting in conditions like rickets or osteomalacia, all of which reflect inadequate mineralization of bone, enhanced compensatory skeletal demineralization, resultant decreased calcium ion blood concentrations, and increases in the production and secretion of parathyroid hormone. Increases in parathyroid hormone stimulate the mobilization of skeletal calcium and the renal excretion of phosphorus. This enhanced mobilization of skeletal calcium leads towards porotic bone conditions. Ordinarily, while vitamin D3 is made naturally via photochemical processes in the skin, both itself and vitamin D2 can be found in various food and pharmaceutical sources as dietary supplements. The principal biological function of vitamin D is the maintenance of normal levels of serum calcium and phosphorus in the bloodstream by enhancing the efficacy of the small intestine to absorb these minerals from the diet. At the liver, vitamin D3 or D2 is hydroxylated to 25-hydroxyvitamin D and then finally to the primary active metabolite 1,25-dihydroxyvitamin D in the kidney via further hydroxylation. This final metabolite binds to endogenous vitamin d receptors, which results in a variety of regulatory roles - including maintaining calcium balance, the regulation of parathyroid hormone, the promotion of the renal reabsorption of calcium, increased intestinal absorption of calcium and phosphorus, and increased calcium and phosphorus mobilization of calcium and phosphorus from bone to plasma to maintain balanced levels of each in bone and the plasma. In particular, calcitriol interacts with vitamin D receptors in the small intestine to enhance the efficiency of intestinal calcium and phosphorous absorption from about 10-15% to 30-40% and 60% increased to 80%, respectively. Furthermore, calcitriol binds with vitamin D receptors in osteoblasts to stimulate a receptor activator of nuclear factor kB ligand (or RANKL) which subsequently interacts with receptor activator of nuclear factor kB (NFkB) on immature preosteoclasts, causing them to become mature bone-resorbing osteoclasts. Such mature osteoclasts ultimately function in removing calcium and phosphorus from bone to maintain blood calcium and phosphorus levels. Moreover, calcitriol also stimulates calcium reabsorption from the glomerular filtrate in the kidneys. Additionally, it is believed that when calcitriol binds with nuclear vitamin D receptors, that this bound complex itself binds to retinoic acid X receptor (RXR) to generate a heterodimeric complex that consequently binds to specific nucleotide sequences in the DNA called vitamin D response elements. When bound, various transcription factors attach to this complex, resulting in either up or down-regulation of the associated gene's activity. It is thought that there may be as much as 200 to 2000 genes that possess vitamin D response elements or that are influenced indirectly to control a multitude of genes across the genome. It is in this way that cholecalciferol is believed to function in regulating gene transcription associated with cancer risk, autoimmune disorders, and cardiovascular disease linked to vitamin D deficiency. In fact, there has been some research to suggest calcitriol may also be able to prevent malignancies by inducing cellular maturation and inducing apoptosis and inhibiting angiogenesis, exhibit anti-inflammatory effects by inhibiting foam cell formation and promoting angiogenesis in en

Pharmacodynamics

The in vivo synthesis of the predominant two biologically active metabolites of vitamin D occurs in two steps. The first hydroxylation of vitamin D3 cholecalciferol (or D2) occurs in the liver to yield 25-hydroxyvitamin D while the second hydroxylation happens in the kidneys to give 1, 25-dihydroxyvitamin D. These vitamin D metabolites subsequently facilitate the active absorption of calcium and phosphorus in the small intestine, serving to increase serum calcium and phosphate levels sufficiently to allow bone mineralization. Conversely, these vitamin D metabolites also assist in mobilizing calcium and phosphate from bone and likely increase the reabsorption of calcium and perhaps also of phosphate via the renal tubules. There exists a period of 10 to 24 hours between the administration of cholecalciferol and the initiation of its action in the body due to the necessity of synthesis of the active vitamin D metabolites in the liver and kidneys. It is parathyroid hormone that is responsible for the regulation of such metabolism at the level of the kidneys.