Pharmacological dose

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. 

L-Fohc acid is available as a crystalline dihydrate containing 8% water. Approximately 80% of the commercial production is consumed for feed enrichment in animal nutrition. FoHc acid is being offered by the pharmaceutical industry for therapeutic and prophylactic use (see Pharmaceuticals). Pharmacological doses of fohc acid are commonly used as a rescue dose during cancer chemotherapy, in women using oral contraceptives, and alcohoHcs. Several studies have provided evidence that multivitamins or foHc acid (0.8—4 mg/day) supplementation prevent the majority of neural tube defects (101). 

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]. 

They differ to some extent from signs and symptoms that occur during anaphylaxis not associated with anesthesia. Early subjective symptoms such as malaise, pruritus, sensation of heat, and dizziness are absent in the anesthetized patient. Cutaneous signs in a completely wrapped patient may escape the attention of the anesthetist. The increase in heart rate, a decrease in blood pressure and an increase in airway resistance may be initially misinterpreted as a result of a pharmacological dose-related effect of the drugs, or of excessively light anesthesia. Many differential diagnoses have to be considered (table 1). 

The polyamines spermidine and spermine (Figure 31-4) function in cell proliferation and growth, are growth factors for culmred mammalian cells, and stabilize intact cells, subcellular organelles, and membranes. Pharmacologic doses of polyamines are hypothermic... 

Liu, C., Russell, R.M., and Wang, X.D., Exposing ferrets to cigarette smoke and a pharmacological dose of beta-carotene supplementation enhance in vitro retinoic acid catabolism in lungs via induction of cytochrome P450 enzymes, J. Nutr., 133, 173, 2003. 

Van Den Heuvel, C. J., Reid, K. J. Dawson, D. (1997). Effect of atenolol on nocturnal sleep and temperature in young men reversal by pharmacological doses of melatonin. Physiol. Behav. 61, 795-802. 

Borel P, Grolier P, Mekki N, Boirie Y, Rochette Y, Le Roy B, Alexandre-Gouabau MC, Lairon D and Azais-Braesco V. 1998. Low and high responders to pharmacological doses of fi-carotene proportion in the population, mechanisms involved and consequences on (3-carotene metabolism. J Lipid Res 39 2250-2260. 

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. 

Nicotinic acid, when given at the rate of several hundred milligrams a day, has pharmacological effects of which cerebral vasodilation is one. Nicotinamide does not have this effect, and hence the pharmacological effects of nicotinic acid probably do not involve simple replacement of a deficiency in an enzyme system. The fact that nicotinic acid itself in pharmacological doses appears to be of Implications for Advance in Psychiatry... 

Figure 12.10 The effects of cortisol. These can be divided into two classes, (i) Physiological levels of cortisol result in changes that maintain the blood glucose level, (ii) Higher levels (pharmacological doses) have an anti-inflammatory effect and a central effect on wellbeing. It is the breakdown of protein that provides amino acids, which along with glucose are used to synthesise glutamine (Chapter 8).

The distinctive feature of a-adrenoblockers is their ability to reduce the pressor effect of pharmacological doses of epinephrine (adrenaline). 

Lactation Advise mothers taking pharmacologic doses not to nurse. 

Growth Inhibit growth (pharmacologic doses) Inhibition of cell division and DNA synthesis... 

Pharmacologic doses in women stimulate growth of facial and body hair and produce deepening of the voice, enlargement of clitoris, frontal baldness and prominent musculature. Natural androgens stimulate erythrocyte production. 

VII.a.2.2. Treatment. Treatment of established vitamin D deficiency requires much larger doses of vitamin D, such as calciferol tablets of 1 mg (40,000 units) daily. Newer but more expensive preparations such as alfa-calcidol and calcitriol are very effective, and are particularly valuable in patients with renal failure who are unable to hydroxylate calciferol. Patients treated with pharmacological doses of vitamin D preparations must be monitored by checking serum calcium at regular intervals because of the risk of inducing hypercalcaemia. This should always be suspected if patients develop thirst, nausea or vomiting. The newer hydroxylated preparations have a shorter effective half-life, and therefore problems of overdosage are quicker to resolve once identified. 

Pharmacokinetics Metabolized to thiamine pyrophosphate (active) in the liver. At dietary levels thiamine is completely distributed to tissues. At pharmacologic doses, excess thiamine is excreted in urine. 

Absorbed ptemutagen activation deactivation transport Pharmacologic dose mg/kg... 

Pharmacologic doses of pyridoxine (vitamin B6 ) enhance the extracerebral metabolism of levodopa and may therefore prevent its therapeutic effect unless a peripheral decarboxylase inhibitor is also taken. Levodopa should not be given to patients taking monoamine oxidase A inhibitors or within 2 weeks of their discontinuance because such a combination can lead to hypertensive crises. 

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