Vitamin pharmacology

Up to 80% of oral doses of ascorbic acid are absorbed in humans with intakes of less than 0.2 g of vitamin C. Absorption of pharmacological doses ranging from 0.2 g to 12 g results in an inverse relationship, with less than 20% absorption at the higher doses. A single oral dose of 3 g has been reported to approach the absorptive capacity (tissue saturation) of the human intestine. Higher blood levels can be attained by providing multiple divided vitamin C doses per day. 

Alimentary biotin deficiency is rare. It may, however, occur in patients on long-term parenteral nutrition lacking biotin or in persons who frequently consume raw egg white. Raw egg white contains a biotin-binding glycoprotein, called avidin, which renders biotin biologically unavailable. Pharmacological doses of the vitamin (1-10 mg/d) are then used to treat deficiency symptoms. There are no reports of toxicity for daily oral doses up to 200 mg and daily intravenous doses of up to 20 mg [2]. 

Oral calcium has long been used for the treatment of osteoporosis, both in the form of dietary and pharmacological supplements. In patients with calcium deficiency, oral calcium at doses of 1000-1500 mg/day corrects a negative calcium balance and suppresses PTH secretion. Sufficient calcium intake is most important for the acciual of peak bone mass in the young, but is also considered the basis of most anti-osteoporotic regimens. In the elderly, supplementation with oral calcium and vitamin D reduces the risk of hip fracture by about 30 4-0%. 

The pharmacological and/or adverse effects of a drug can be reversed by co-administration of drugs which compete for the same receptor. For example, an opioid receptor antagonist naloxone is used to reverse the effects of opiates. Drugs acting at the same site with opposite effects also can affect each other, e.g. the reduction in the anticoagulant effect of warfarin by vitamin K. 

Vitamin K content of enteral nutrition formulas may affect pharmacological activity. Monitor and titrate dose to maintain therapeutic international normalized ratio (INR)... 

Check parathyroid hormone (PTH), vitamin D and precursors, magnesium, and phosphate levels ° Pharmacological causes of decreased ionized calcium may include excess infusions of citrate, EDTA, lactate, fluoride poisoning, foscarnet, cinacalcet, bisphosphates, or unrelated increase in serum phosphate or decrease in serum magnesium levels... 

Ansell J, Hirsh J, Poller L, et al. The pharmacology and management of the vitamin K antagonists The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004 126 204S-233S. 

Treatment Nonpharmacologic treatments of muscle cramping that occurs during hemodialysis include decreasing the ultrafiltration rate and accurately determining the dry weight. Pharmacologic measures include vitamin E, which is administered at doses of 400 IU daily. Other options that are not as well studied include oxazepam and prazosin. 

There are no approved pharmacologic treatments for atrophic AMD. The Age-Related Eye Disease Study showed that a supplement containing ascorbic acid 500 mg, vitamin E 400 IU, beta carotene 15 mg, zinc oxide 80 mg, and cupric oxide 2 mg reduced the rate of clinical progression of all types of AMD by 28% in patients with at least intermediate macular degeneration. No benefit was seen in patients with earlier stages of age-related maculopathy however, the duration of the study may have been insufficient to detect this benefit.25... 

The underlying cause of anemia (e.g., blood loss iron, folic acid, or vitamin B12 deficiency or chronic disease) must be determined and used to guide therapy. As discussed previously, patients should be evaluated initially based on laboratory parameters to determine the etiology of the anemia (see Fig. 63-3). Subsequently, the appropriate pharmacologic treatment should be initiated based on the cause of anemia. 

EN formulas contain vitamin K, which can antagonize the pharmacologic activity of warfarin. The vitamin K content of EN formulas generally has been adjusted down over the past... 

Marcus, R., Agents affecting calcification and bone turnover calcium, phosphate, parathyroid hormone, vitamin D, calcitonin, and other compounds, in Goodman and Gilman s The Pharmacological Basis of Therapeutics, 9th ed., Hardman, J.G. and Limbird, L.E., Eds., McGraw-Hill, New York, 1996, chap. 61. 

Shvedova, A.A. et al. (2007) Vitamin E deficiency enhances pulmonary inflammatory response and oxidative stress induced by single-walled carbon nanotubes in C57BL/6 mice. Toxicology and Applied Pharmacology, 221 (3), 339-348. 

It should be noted that pharmacological vitamin E is not a free natural RRR-a-tocopherol or synthetic All rac a-tocopherol but its acetate ester. a-Tocopheryl acetate has the phenolic hydroxyl group blocked and therefore, is not a genuine antioxidant, but this compound is very rapidly hydrolyzed in vivo into a-tocopherol. It is interesting that the biological activity of a-tocopheryl acetate is the same as that of a-tocopherol in humans but significantly lower in rats [30]. ( A man is not a rat Professor KU Ingold.)... 

Since glutathione is synthesized in cells in relatively huge amounts, it is seldom applied as pharmacological antioxidant. Furthermore, the mechanism of its antioxidant activity is not so simple as that of vitamins E and C. The major reason is that the GS radical formed during scavenging of free radicals by GSH does not disappear by dimerization but participates in the chain reaction, producing superoxide (Reactions (20)-(23)). Furthermore, it has recently been shown that contrary to previous findings the rate constant for the reaction of GSH with superoxide is relatively small (200-1000 lmol-1 s-1) [211,223],... 

Homocystinuria can be treated in some cases by the administration of pyridoxine (vitamin Bs), which is a cofactor for the cystathionine synthase reaction. Some patients respond to the administration of pharmacological doses of pyridoxine (25-100 mg daily) with a reduction of plasma homocysteine and methionine. Pyridoxine responsiveness appears to be hereditary, with sibs tending to show a concordant pattern and a milder clinical syndrome. Pyridoxine sensitivity can be documented by enzyme assay in skin fibroblasts. The precise biochemical mechanism of the pyridoxine effect is not well understood but it may not reflect a mutation resulting in diminished affinity of the enzyme for cofactor, because even high concentrations of pyridoxal phosphate do not restore mutant enzyme activity to a control level. 

Benzimidazole is an important heterocyclic nucleus in the field of medicinal chemistry. The most prominent benzimidazole compound in nature is N-ribosyldimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12. The versatile nature of benzimidazole makes it a highly explored molecule in medicinal chemistry. A number of pharmacological activities are associated with benzimidazole derivatives such as anthelmintic, antiulcer, antipsychotic, proton pump inhibitor, antianxiety, anti-emetic and sedative, vasodilator, anticancer, analgesic, antihistaminic, antifungal, antiviral and antimicrobial. 

X Receptor alpha and beta, Liver X Receptor alpha and beta, and Vitamin D Receptor, International Union of Pharmacology, LXII. 

Optimal therapy consists in parenteral administration of cyanocobalamin or hydroxycobalamin (Vitamin Lullmann, Color Atlas of Pharmacology... 

Vitamin D hormone is derived from vitamin D (cholecalciferol). Vitamin D can also be produced in the body it is formed in the skin from dehydrocholesterol during irradiation with UV light. When there is lack of solar radiation, dietary intake becomes essential, cod liver oil being a rich source. Metaboli-cally active vitamin D hormone results from two successive hydroxylations in the liver at position 25 ( calcifediol) and in the kidney at position 1 ( calci-triol = vit. D hormone). 1-Hydroxylation depends on the level of calcium homeostasis and is stimulated by parathormone and a fall in plasma levels of Ca or phosphate. Vit D hormone promotes enteral absorption and renal reabsorption of Ca and phosphate. As a result of the increased Ca + and phosphate concentration in blood, there is an increased tendency for these ions to be deposited in bone in the form of hydroxyapatite crystals. In vit D deficiency, bone mineralization is inadequate (rickets, osteomalacia). Therapeutic Liillmann, Color Atlas of Pharmacology... 

Pharmacology Vitamin C, a water-soluble vitamin, is an essential vitamin in man however, its exact biological functions are not fully understood. It is essential for the formation and the maintenance of intercellular ground substance and collagen, for catecholamine biosynthesis, for synthesis of carnitine and steroids, for conversion of folic acid to folinic acid and for tyrosine metabolism. 

Pharmacology Niacin, vitamin B3, is the common name for nicotinic acid and niacinamide (nicotinamide). Nicotinic acid is present in the body as its active form, nicotinamide (niacinamide). 

Although nicotinic acid and nicotinamide function identically as vitamins, their pharmacologic effects differ. In large doses (up to 6 g/day), nicotinic acid is effective in reducing serum lipids (low-density lipoprotein [LDL], high-density lipoprotein [HDL], triglycerides, and lipoprotein A. Nicotinic acid produces vasodilation and increased blood flow due to histamine release. Nicotinamide does not affect blood lipid levels or the cardiovascular system. 

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