OZICAL 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

Dosage

Children: Refer to specific drug guidelines or BNF for Children for accurate dosing information.

Adults: Refer to specific drug guidelines or BNF for accurate dosing information.

Mechanism of action

The mechanism of action of complex drugs can vary widely depending on their composition. Generally, these agents may act by modulating receptor activity, inhibiting enzyme pathways, or altering cellular signaling pathways. For instance, they may function as agonists or antagonists at specific receptors, influencing physiological responses such as neurotransmission or inflammation.

Pharmacodynamics

The pharmacodynamics of complex drugs involves understanding how they affect the body over time, including their potency, efficacy, and duration of action. These drugs may exhibit dose-dependent effects, where higher doses lead to increased therapeutic actions or side effects. Additionally, the interactions between the components of a complex formulation can result in synergistic or antagonistic effects, impacting the overall therapeutic outcome.

Pharmacokinetics

Pharmacokinetics of complex drugs encompasses the absorption, distribution, metabolism, and excretion (ADME) of the drug components. Absorption can be influenced by the formulation, while distribution may vary based on the lipophilicity and protein binding of each component. Metabolism often occurs in the liver, with various enzymes involved, and excretion typically takes place via renal or biliary pathways. The half-life of complex drugs can vary significantly based on their individual components.

Pregnancy

Consult healthcare provider. Risk-benefit assessment is essential before use.

Breast-feeding

Consult healthcare provider. Monitor for potential effects on the infant.

Storage

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

Indications

• Nutritional supplementation
• Bone health support
• Growth and development in children
• Muscle repair and recovery
• Hydration

Dosage

Children: Refer to pediatric dietary guidelines; daily intake varies by age, generally 2-2.5 servings per day for children.

Adults: Refer to dietary guidelines for recommended daily intake of dairy products, typically 2-3 servings per day.

Mechanism of action

The components of milk, particularly its proteins and fats, are digested and metabolized to provide energy and essential nutrients. Lactose is broken down into glucose and galactose by the enzyme lactase. Calcium and vitamin D are crucial for bone metabolism, while proteins support muscle and tissue repair and growth.

Pharmacodynamics

The consumption of milk leads to increased levels of calcium and other minerals in the bloodstream, which are vital for maintaining bone density and structure. The proteins in milk contribute to muscle protein synthesis and repair, alongside providing a source of energy. The bioactive compounds in milk may also have protective effects against certain diseases.

Pharmacokinetics

After ingestion, milk is digested in the stomach and small intestine, where nutrients are absorbed into the bloodstream. The absorption of lactose depends on the presence of lactase. The fats are emulsified and absorbed through the lymphatic system. Calcium absorption can be enhanced by vitamin D. The metabolic effects vary based on individual tolerance and the presence of digestive enzymes.

Adverse effects

• Lactose intolerance may cause gastrointestinal discomfort, bloating, and diarrhea in sensitive individuals.
• Allergic reactions may occur in individuals with a milk allergy, potentially leading to anaphylaxis.

Precautions

• Use with caution in individuals with lactose intolerance or milk allergies.
• Consult a healthcare provider before introducing milk into the diet of infants.

Pregnancy

Milk is generally considered safe during pregnancy, providing essential nutrients such as calcium and vitamin D. However, pregnant individuals should opt for pasteurized milk to reduce the risk of infections.

Breast-feeding

Milk can be consumed during breastfeeding, but it is important to monitor for any allergic reactions in the infant, especially if there is a family history of allergies.

Storage

Store milk in a cool place, preferably refrigerated at 4°C or lower. Consume before the expiration date to ensure safety and quality.

Formulations

• Whole milk
• Skimmed milk
• Low-fat milk
• Condensed milk
• Evaporated milk
• Milk powder

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.