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Analgesic/Antipyretic/Vitamins.
Pharmacology: Pharmacodynamics: The neurotropic vitamin B1, B6, B12 are essential for nerve metabolism to function normally. Disturbances in this metabolism often due to deficiencies in these factors from the vitamin B complex and painful diseases in the nerve system can be caused false regulation of organ functions is frequently a secondary development following primary nerve lesions.
Paracetamol is safe and reliable analgesic and thus can be used in particular in the treatment of acute and highly painful forms of these diseases.
Pharmacokinetics: Paracetamol: Paracetamol is readily absorbed from the gastrointestinal tract with peak plasma concentrations occurring about 10 to 50 minutes after oral doses. Paracetamol is distributed into most body tissues. It crosses placenta and is present in breast milk. Plasma-protein binding is negligible at usual therapeutic concentrations but increases with increasing concentrations. The elimination half-life varies from about 2 to 3 hours.
Paracetamol is metabolized mainly in the liver and excreted in the urine mainly as the gluconate and sulphate conjugates. Less than 5% is excreted as unchanged paracetamol. A minor hydroxylated metabolite [N-acetyl-p-benzoquinone imine], is usually produced in very small amounts by cytochrome P450 isoenzymes in the liver and kidney. It is usually detoxified by conjugation with glutathione but may accumulate after paracetamol overdosage and cause tissue damage.
Vitamin B1: Small amounts of thiamine are well absorbed from the gastrointestinal tract after oral doses, but the absorption of doses larger than about 5 mg is limited. It is widely distributed to most body tissues, and appears in breast milk. Within the cell, thiamine is mostly present as the diphosphate. Thiamine is not stored to any appreciable extent in the body and amounts in excess of the body's requirements are excreted in the urine unchanged as metabolites.
Vitamin B6: Pyridoxine is absorbed from the gastrointestinal tract after oral doses and is converted to the active forms pyridoxal phosphate and pyridoxamine phosphate. They are stored mainly in the liver where there is oxidation to 4-pyridoxic acid and other inactive metabolites which are excreted in the urine. Pyridoxal crosses the placenta and is distributed into breast milk.
Vitamin B12: Vitamin B12 substances bind to intrinsic factor, a glycoprotein secreted by the gastric mucosa, and are then actively absorbed from the gastrointestinal tract. Absorption is impaired in patients with an absence of intrinsic factor, with a malabsorption syndrome or with disease or abnormality of the gut, or after gastrectomy. Absorption from the gastrointestinal tract can also occur by passive diffusion; little of the vitamin present in food is absorbed in this manner although the process becomes increasingly important with larger amounts such as those used therapeutically.
Vitamin B12 is extensively bound to specific plasma proteins called transcobalamins; transcobalamin II appears to be involved in the rapid transport of the cobalamin to tissues. Vitamin B12 is stored in the liver, excreted in the bile, and undergoes extensive enterohepatic recycling; part of a dose is excreted in the urine, most of it in the first 8 hours, urinary excretion, however, accounts for only a small fraction in the reduction of total body stores acquired by dietary means, Vitamin B12 diffuses across the placenta and also appears in breast milk.
