Vitamin overdose

The symptoms that are commonly reported in vitamin overdose are listed in Table 2. 

Since vitamin overdose can produce unexpected, often vague, signs and symptoms, physicians should ask patients who present with inexplicable symptoms, including those listed in Table 2 (15), about their use of unusual or unapproved therapies, including vitamins in megadoses (10). It has been suggested that a medical history is not complete without vitamin/mineral supplement information (6). 

Acute adrenal insufficiency Pheochromocytoma Familial hypocalciuric hypercalcemia Idiopathic hypercalcemia of infancy Vitamin overdose Vitamin D Vitamin A... 

IV. Diagnosis of vitamin overdose is usually based on a history of ingestion. Cutaneous flushing and pruritus suggest a niacin reaction but may be caused by other histaminergic agents. 

Proponents of this vitamin therapy often understand the risks of vitamin overdose. The scientific literature reports several well documented cases, sometimes with fatal consequences. Fat-soluble vitamins are of the Itighest concern in this respect, both acute (a single extremely large dose) or chrotuc (from continuous large doses) toxicity is known for them. It is not an accident that three of the four fat-soluble vitamins have widely accepted UL values, whereas water-soluble vitamins rarely have rehably known upper hmits. Studies of both hypo- and hyper-vitantin-osis contain enough scientific literature to fill libraries, and this short stoiy carmot even scratch the surface. Table 3.4 displays a few vitamins with reliable UL values and lists the symptoms of overdose. Care must be taken, as the toxic dose is usually lower for children than for adults, and the symptoms in kids may be more serious. 

Vitamin overdoses (hypervitaminoses)— The best known vitamin toxicities are those which result from vitamin A and vitamin D, because (1) these vitamins are fat soluble, (2) small amounts of them have strong effects, and (3) they tend to accumulate in the liver. Toxic effects do not occur so readily with vitamins E and K, which are also fat-soluble, unless high potency supplements are taken. 

Reported cases of vitamin toxicity owing to overdose are usually associated with increased over-the-counter availabiHty of supplemental vitamins and indiscriminate supplementation. The misconception that if a Httle is good a lot is better has compounded toxicological problems with the vitamins. Eat-soluble vitamins tend to accumulate in the body with relatively inactive mechanism for excretion and cause greater toxicological difficulties than do water-soluble vitamins. 

The effects of the steroid hormone calcitriol (see p. 330) in bone are complex. On the one hand, it promotes bone formation by stimulating osteoblast differentiation (top). This is particularly important in small children, in whom calcitriol deficiency can lead to mineralization disturbances (rickets see p.364). On the other hand, calcitriol increases blood Ca "" levels through increased Ca "" mobilization from bone. An overdose of vitamin D (chole-calciferol), the precursor of calcitriol, can therefore have unfavorable effects on the skeleton similar to those of vitamin deficiency (hypervitaminosis see p.364). 

Since only a few vitamins can be stored (A, D, E, Bi2), a lack of vitamins quickly leads to deficiency diseases. These often affect the skin, blood cells, and nervous system. The causes of vitamin deficiencies can be treated by improving nutrition and by administering vitamins in tablet form. An overdose of vitamins only leads to hypervita mi noses, with toxic symptoms, in the case of vitamins A and D. Normally, excess vitamins are rapidly excreted with the urine. 

The absorption of vitamins K2, which are found mainly in cheese, curd cheese, and natto, is much higher and may be almost complete. Thus the nutritional importance of menaquinones is often underestimated. The vitamin K activity is related to the activation of specific proteins involved in blood clotting and bone metabolism. Clinical vitamin deficiency due to dietary inadequacy is rare or nonexistent in healthy adults, thanks to the widespread distribution of the vitamin K in foodstuffs and the microbiological flora of the gut, which synthesizes menaquinones. Only infants up to 6 months are at risk of bleeding due to a vitamin K deficiency. No data on negative effects of an overdose of vitamin K are found [417]. 

Dehciency can lead to a bone-softening disease, like rickets in children and osteomalacia in adults, and it can contribute to osteoporosis. Vitamin D overdose is rare, but it can lead to hypercalcemia and it can develop in anorexia, nausea, and vomiting. Vitamin D is relatively stable in fat solutions, e.g., it is not inactivated by pasteurization or sterilization. It oxidizes in contact with air and in acid solutions. 

In foods vitamin B2 occurs free or combined both as FAD and FMN and complexed with proteins. Riboflavin is widely distributed in foodstnffs, but there are very few rich sources. Only yeast and liver contain more than 2mg/100g. Other good sources are milk, the white of eggs, fish roe, kidney, and leafy vegetables. Since riboflavin is continuously excreted in the urine, deficiency is qnite common when dietary intake is insufficient. The symptoms of deficiency are cracked and red lips, inflammation of the lining of the month and tongue, mouth ulcers, cracks at the comer of the mouth, and sore throat. Overdose of oral intake present low toxicity, probably explained by the limited capacity of the intestinal absorption mechanism [417]. 

Deficiency of this coenzyme can lead to many manifestations. Clinical signs include retarded growth, acrodynia, alopecia, skeletal changes and anemia, while changes in neurotransmitters, such as dopamine, serotonin, norepinephrine (noradrenaline), tryptamine, tyramine, histamine, y-aminobutyric acid, and taurine, affect the brain function and can lead to seizures and convulsions. An overdose of vitamin Bg leads to neuronal damage and sensory and motor effects [417],... 

Recommended dietary allowances for vitamins have proved to be useful guidelines however it has to be appreciated that these guidelines are not more than estimates made from experiments on only a limited number of subjects. These recommended dietary allowances also need periodic reevaluation. While vitamin deficiencies due to inadequate intakes are encountered in developing countries, few cases are seen in the Western world apart from patients with an increased risk for deficiencies such as diabetics or alcoholics. On the contrary, the widely held belief that vitamins promote better health is deceptive and may lead to overdose disorders. 

Calcipotriol is a vitamin D3 derivative which is used as a topical agent in the treatment of psoriasis. Although not completely elucidated its mechanism of action seems to be based on inhibition of the proliferation and stimulation of the differentiation of epidermal keratinocytes. Adverse effects include irritation of the skin but also urticarial reactions. Calcipotriol has 100 fold less vitamin D activity as its active vitamin D3 metabolite calcitriol. However, calcipotriol in overdose can cause symptoms of hypercalcemia. 

The effects of most vitamin B overdoses have not been documented, although large dosages of pyridoxine have been reported to cause peripheral neuropathies. Ataxia and numbness of the hands and feet and impairment of the senses of pain, touch, and temperature may result. Excessive niacin intake may result in flushing, pruritus, and gastrointestinal disturbances. These symptoms are due to niacin s ability to cause the release of histamine. Large dosages of niacin can result in hepatic toxicity. 

Therapeutically, vitamin K is used in prophylaxis and treatment of deficiency of clotting factor due to dietary deficiency of vitamin K, chronic antimicrobial therapy, malabsorption syndrome, obstructive jaundice, liver diseases such as cirrhosis and hepatitis, in neonates to prevent or treat haemorrhagic disease of new born to counteract the overdosing of oral anticoagulants... 

Direct organ toxicity. Some substances may directly damage cells of a particular organ or system, either because they or their metabolites are specifically toxic to these cells, or because they are concentrated in one area, e.g. the renal fluoride ion toxicity of methoxyflurane, or the liver damage that occurs in paracetamol overdose because of a toxic intermediate product binding to hepatocytes. Secondary effects. Some effects are only indirectly related to the action of the drug, e.g. vitamin deficiency in patients whose gut flora have been modified by broad-spectrum antibiotics. 

Be cautious about overdosing on dietary supplements. Large doses of some nutrients act as drugs and prolonged heavy use can reach toxic levels. For example, too much Vitamin A can cause headaches, nausea, and diarrhea. High doses of Vitamin D can cause kidney damage. Too much iron can harm your liver. 

Other drug-delivery systems may include double emulsions, usually W/O/W, for transporting hydrophilic dmgs such as vaccines, vitamins, enzymes, hormones [441], The multiple emulsion also allows for slow release of the delivered drug and the time-release mechanism can be varied by adjusting the emulsion stability. Conversely, in detoxification (overdose) treatments, the active substance migrates from the outside to the inner phase. 

Chloramphenicol Palmitate Chloramphenicol has concentration-dependent incompatibility with many drugs. Chloramphenicol has severe toxic effects, and overdose may be treated by hemoperfusion of charcoal. It interacts with coumarin anticoagulants, some oral hypoglycemics, antiepileptic drugs, and nutrients such as iron and vitamin B12. 

It is now also recognized that overdoses of certain vitamins, especially some of the fat-soluble ones, may result in serious toxic effects. For this reason, the addition of vitamins to foods should be carefully controlled. 

Overdose of drugs with a narrow therapeutic range and/or unfavorable pharmacokinetics (e.g., phenprocoumon or warfarin, which exert their action in a delayed and indirect manner by inhibition of vitamin K biosynthesis). 

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