vitamin D

Action and Spectrum

Actions and Spectrum: 

vitamin D is a fat-soluble vitamin that generally plays key role in several physiological processes in the human body. Its primary action is related to calcium and phosphorus metabolism and bone health.  

• Calcium absorption: vitamin D promotes calcium absorption from the intestine, ensuring adequate calcium levels in the bloodstream. This is essential for maintaining proper bone mineralization, muscle function, and nerve transmission. 
• Bone health: vitamin D works with calcium to support bone health. It helps regulate the deposition and resorption of calcium in bones, promoting bone mineralization and preventing conditions like rickets in children and osteomalacia in adults. 
• Immune function: vitamin D plays a role in modulating the immune system. It has been shown to regulate the production and function of various immune cells, which helps defend against infections and reduces the risk of autoimmune diseases. 
• Hormone regulation: vitamin D acts as a hormone in the body, influencing the function of various tissues and organs. 
• Muscle function: Adequate vitamin D levels are essential for muscle health and function. It helps maintain muscle strength and coordination, and decreased vitamin D levels have been typically associated with an increased risk of falls and muscle weakness. 

The spectrum of vitamin D refers to the different forms of the vitamin that exist. The main forms of vitamin D are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). vitamin D2 is obtained from plant sources and produced when fungi or yeasts are exposed to ultraviolet (UV) radiation. vitamin D3 is generally synthesized in the skin when exposed to UVB radiation from sunlight and is also found in some animal-based food sources. Both forms are biologically active, but vitamin D3 is considered more potent and effective in raising blood levels of vitamin D. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Hypercalcemia 

Lethargy 

Vomiting 

Confusion 

Arrhythmias 

Nausea 

Headache 

Dry mouth 

Constipation 

Sluggishness 

Metallic taste 

Muscle or bone pain 

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

Contraindication 

• Hypercalcemia: vitamin D supplementation should be used cautiously in individuals with hypercalcemia, characterized by elevated blood calcium levels. Excessive vitamin D intake can increase calcium levels, leading to potential complications. 
• Hypervitaminosis D: Prolonged and excessive vitamin D intake can result in hypervitaminosis D, a condition characterized by abnormally high vitamin D levels in the body. This can lead to nausea, vomiting, poor appetite, constipation, weakness, and kidney problems. 
• Certain medical conditions: vitamin D supplementation may need to be monitored or adjusted in individuals with certain medical conditions, including kidney disease, liver disease, hyperparathyroidism, sarcoidosis, and certain types of cancer. These conditions can affect how the body processes and utilizes vitamin D. 
• Medications: Some medications can interact with vitamin D or affect its metabolism in the body. These may include certain anticonvulsants, glucocorticoids, antifungal medications, and some cholesterol-lowering drugs. Consultation with a healthcare professional is vital to evaluate potential interactions. 
• Allergies or sensitivities: Individuals with known allergies or sensitivities to vitamin D or its ingredients should avoid vitamin D supplementation and discuss alternative options with their healthcare provider. 
• Pregnancy and breastfeeding: Adequate vitamin D is vital for pregnant and breastfeeding women; however, consulting with a healthcare professional for appropriate dosing and monitoring is recommended to ensure optimal levels without exceeding safe limits. 

Caution 

• Recommended Dosage: Following the recommended dosage guidelines for vitamin D supplementation is essential. Excessive vitamin D intake can lead to hypervitaminosis D, causing nausea, vomiting, poor appetite, constipation, weakness, and kidney problems.  
• Interactions with Medications: vitamin D supplements can interact with certain medications, including corticosteroids, anticonvulsants, and cholesterol-lowering drugs. These interactions can affect the medication’s effectiveness and vitamin D supplementation.  
• Medical Conditions: Individuals with certain medical conditions, such as kidney disease, liver disease, hyperparathyroidism, or sarcoidosis, may require special monitoring and dosage adjustments when supplementing with vitamin D. It is essential to consult with a healthcare professional if you have any underlying health conditions. 
• Sunlight Exposure: vitamin D can be synthesized in the skin through exposure to sunlight. While the sunlight is a natural source of vitamin D, excessive exposure without appropriate sun protection can enhance the risk of skin damage and skin cancer. It is vital to balance obtaining vitamin D through sunlight and taking the necessary precautions to protect your skin. 
• Allergies or Sensitivities: Certain individuals may have allergies or sensitivities to vitamin D supplements or their ingredients.  
• Monitoring Levels: Regular monitoring of vitamin D levels is recommended, especially for individuals who are supplementing with high doses or have specific medical conditions. This helps ensure that vitamin D levels remain within the optimal range and avoid potential complications associated with deficiency or excess. 

Pregnancy / Lactation

Pregnancy consideration:  

US FDA pregnancy category: C (ergocalciferol) 

Lactation:   

Excreted into human milk: Yes 

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

vitamin D, primarily in vitamin D3 (cholecalciferol), exhibits its pharmacological effects through metabolic conversions. Following ingestion or synthesis in the skin upon exposure to sunlight, vitamin D is hydroxylated in the liver to form 25-hydroxyvitamin D. This is the primary circulating form of the vitamin D and is used to indicate vitamin D status.

Further hydroxylation occurs in the kidneys to produce the biologically active form, 1,25-dihydroxyvitamin D, also known as calcitriol. Calcitriol binds to the vitamin D receptor, which is present in various tissues throughout the body.

It exerts its effects by regulating the expression of genes involved in calcium and phosphorus metabolism, bone health, immune function, muscle function, hormone regulation, and other physiological processes. The pharmacological actions of vitamin D, mediated by calcitriol and the VDR, are essential for maintaining calcium homeostasis, bone mineralization, and overall health. 

Pharmacodynamics: 

Mechanism of action: The mechanism of action of vitamin D primarily involves its binding to the vitamin D receptor (VDR) in target tissues, leading to the regulation of gene expression and subsequent physiological effects.  

• Receptor Binding: After undergoing hydroxylation in the kidneys, vitamin D is converted to its biologically active form, 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol. Calcitriol binds to the vitamin D receptor, which is present in various tissues throughout the body. 
• VDR Activation: Upon binding to the VDR, calcitriol forms a complex with the receptor, leading to conformational changes and the recruitment of coactivator proteins. 
• Regulation of Gene Expression: The calcitriol-VDR complex acts as a transcription factor, directly influencing gene expression. It binds to specific DNA sequences called vitamin D response elements (VDREs) within the regulatory regions of target genes. This binding regulates the transcriptional activity of these genes, either enhancing or suppressing their expression. 
• Calcium and Phosphorus Homeostasis: The prominent role of vitamin D is to maintain calcium and also phosphorus homeostasis in the body. By regulating the expression of the  genes involved in intestinal calcium absorption, renal calcium reabsorption, and bone mineralization, vitamin D helps ensure adequate levels of these minerals. 
• Bone Health: vitamin D plays a crucial role in bone health by promoting calcium absorption from the intestine and regulating the deposition and resorption of calcium in bones. It helps mineralize the bone matrix and prevents conditions like rickets in children and osteomalacia in adults. 
• Immune Modulation: vitamin D also exerts immunomodulatory effects by regulating gene expression in immune function. It influences the differentiation and function of immune cells, like T cells and macrophages, and helps defend against infections and modulate immune responses. 

Pharmacokinetics: 

Absorption 

In the small intestine, dietary vitamin D and vitamin D supplements undergo passive diffusion and active transport to be absorbed into the bloodstream. The absorption efficiency depends on factors such as vitamin D (D2 or D3), the presence of dietary fats, and the individual’s gut health. 

Distribution 

Once absorbed, vitamin D is bound to vitamin D-binding protein (DBP) and circulated in the bloodstream. It is transported to various tissues and organs throughout the body, along with the liver and kidneys, where it undergoes further metabolic conversions. 

Metabolism 

In the liver, vitamin D is hydroxylated by the enzyme 25-hydroxylase to form 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. This is the main circulating form of the  vitamin D and serves as an indicator of vitamin D status. Further metabolism occurs in the kidneys, where the enzyme 1α-hydroxylase converts 25(OH)D into the biologically active form, 1,25-dihydroxyvitamin D, also known as calcitriol. Calcitriol acts as a hormone and exerts its effects by binding to the target tissues’ vitamin D receptor (VDR). 

Elimination and Excretion 

vitamin D and its metabolites are excreted primarily through the bile and feces. Some small amounts may also be excreted in the urine. The excretion of vitamin D depends on various factors, including renal function and overall vitamin D status. 

Adminstartion

Administration: 

Oral administration 

vitamin D can be administered through various methods, including oral supplements, fortified foods, and sunlight exposure.  

• Oral Supplements: The most common form of vitamin D administration is oral supplements in capsules, tablets, or liquid drops. These supplements typically contain vitamin D3 (cholecalciferol) or, less commonly, vitamin D2 (ergocalciferol). Oral supplements are available over-the-counter and in prescription strengths. A healthcare professional should determine the dosage and frequency of supplementation based on individual needs and vitamin D levels. 
• Fortified Foods: Certain foods are fortified with vitamin D, which means they have vitamin D added during processing. Common examples include fortified milk, cereals, juices, and yogurt. When consuming fortified foods, it is essential to check the labels to determine the amount of vitamin D provided per serving. 
• Sunlight Exposure: Sunlight exposure is a natural way for the body to produce vitamin D. When the skin is generally exposed to ultraviolet B rays from sunlight, a reaction occurs that converts a cholesterol compound in the skin into vitamin D3. The amount of time needed for sun exposure to produce adequate vitamin D varies based on factors such as skin type, geographic location, time of day, season, and use of sunscreen.  
• Intramuscular Injections: In some instances, particularly for individuals with severe vitamin D deficiency or malabsorption issues, a healthcare professional may administer vitamin D injections. These injections typically contain a high vitamin D dosage and are given directly into the muscle. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: vitamin D 

Pronounced:  

Why do we use vitamin D? 

vitamin D has several important uses and benefits in the body.  

• Promotes Bone Health: One of the primary functions of vitamin D is to support calcium absorption and utilization, which is crucial for maintaining strong and healthy bones. It helps properly mineralize bones and teeth, preventing conditions like rickets in children and osteomalacia in adults. 
• Supports Immune Function: vitamin D plays a role in modulating the immune system. It helps regulate the production and function of immune cells, like T cells and macrophages, which are essential for fighting off infections and supporting immune responses. 
• Enhances Muscle Function: Adequate vitamin D levels are essential for muscle health and function. It helps maintain muscle strength and coordination, reducing the risk of falls and improving overall physical performance. 
• Supports Brain Health: Emerging research suggests vitamin D may affect brain health and cognitive function. Ample vitamin D levels have been associated with a diminished risk of cognitive decline, dementia, and certain neurological conditions. 
• Helps Prevent and Manage Chronic Diseases: vitamin D deficiency has been linked to an enhanced risk of various chronic diseases, including cardiovascular diseases, type 2 diabetes, autoimmune diseases, and certain types of cancer. Maintaining optimal vitamin D levels may help reduce the risk and manage these conditions. 
• Regulates Hormonal Balance: vitamin D acts as a hormone in the body, influencing the function of various tissues and organs.