Vitamin C (Ascorbic Acid)

Indications

Vitamin C is a water-soluble vitamin, antioxidant, and essential co-factor for collagen biosynthesis, carnitine and catecholamine metabolism, and dietary iron absorption. Humans are unable to synthesize vitamin C, so they can only obtain it through dietary intake of fruits and vegetables. Citrus fruits, berries, tomatoes, potatoes, and green leafy vegetables are excellent sources of vitamin C. Although most vitamin C is completely absorbed in the small intestine, the percentage of absorbed vitamin C decreases as intraluminal concentrations increase. Proline residues on procollagen require vitamin C for hydroxylation, making it necessary for the triple-helix formation of mature collagen. The lack of a stable triple-helical structure compromises the integrity of the skin, mucous membranes, blood vessels, and bone. Consequently, a deficiency in vitamin C results in scurvy, which presents with hemorrhage, hyperkeratosis, and hematological abnormalities.[1][2][3][4][5]

Vitamin C deficiency usually arises in the setting of decreased intake or increased requirements or losses. Persons at risk for inadequate intake of the vitamin include patients in the following groups:

• The elderly
• Those with alcohol use disorder, anorexia, or cancer
• Practicing food fads
• Those with presumed food allergies
• Receiving unsupplemented parenteral nutrition
• Those on restricted diets secondary to inflammatory bowel disease, gastrointestinal reflux, or Whipple disease
• Those who smoke tobacco products
• Taking medications such as aspirin, indomethacin, oral contraceptives, tetracyclines, and corticosteroids.
• Those who have renal failure due to filtration of water-soluble vitamin C during dialysis
• Those with a complication of interleukin-2 treatment of metastatic renal cell carcinoma
• Receiving liver transplants

Indications

Scurvy

Vitamin C is indicated to prevent and treat scurvy. Scurvy develops 1 to 3 months after initiating a vitamin C deficient diet. Individuals may complain of lethargy, fatigue, malaise, emotional lability, arthralgias, weight loss, anorexia, and diarrhea. They also may experience easy bleeding, bruising, and poor wound healing. The cutaneous manifestations of scurvy include phrynoderma, corkscrew hairs, perifollicular hemorrhage and purpura, edema of the lower extremities, and splinter hemorrhages. Phrynoderma, or enlarged hyperkeratotic hair follicles, initially present on the posterolateral arms. This presentation subsequently generalizes to involve the buttocks, posterior thighs, calves, shins, and back. Corkscrew hairs represent fractured and coiled hairs due to impaired keratin cross-links by disulfide bonds. With time, significant vascular congestion occurs, particularly in the lower extremities, leading to perifollicular hemorrhage and edema. This purpura is occasionally palpable, mimicking a cutaneous vasculitis. Blood vessel wall fragility also results in splinter hemorrhages of the nail bed. Oral disease is prominent among those with pre-existing poor dentition. Individuals may develop hemorrhagic gingivitis, where the gingiva is initially red, swollen, and shiny and later becomes purple, necrotic, and prone to bleeding. Additionally, poorly formed soft teeth are prone to infection. Musculoskeletal disease frequently presents in children. Hemorrhage can be intramuscular, intra-articular, or subperiosteal, leading to pain and pseudoparalysis. Bowing of the long bones, depression of the sternum, and swelling of the costochondral junctions are present on physical examination. Radiographic findings include a transverse metaphyseal radiolucent band (scurvy line or Trummerfeld zone), widening at the zone of calcification (white line of Frankel), a ring of increased density around the epiphysis (Wimberger ring), and metaphyseal spurs with marginal fractures (Pelkan spurs). Reports exist of conjunctival, intraocular, intracerebral, and gastrointestinal bleeding.

Other indications

Daily need increases in patients with conditions like gingivitis, asthma, glaucoma, collagen disorders, heatstroke, arthritis, infections (pneumonia, sinusitis, rheumatic fever), and chronic illnesses. Hemovascular disorders, burns, and delayed wound healing are causes for an increase in the daily intake.

Mechanism of Action