Interactions between drugs and nutrients

Nutrition support teams: past, present, and future

Nutrition support teams have evolved rapidly and grown in numbers since the early 1970s. While not all hospitals have or need nutrition support teams, the team approach has been demonstrated to be an excellent mechanism for identifying patients in need of nutrition support, reducing the complications associated with enteral and parental nutrition, and providing cost-effective nutrition support in a variety of hospital environments. The organization of a nutrition support team is reviewed, and suggestions are outlined for team survival in this uncertain era of health care reform. New JCAHO standards are reported which require performance-based interdisciplinary delivery of nutrition support, and make it more likely that efficiently organized nutrition support teams will thrive and continue to make important contributions to safe and cost-effective health care now and in the immediate future.

Medication-nutrient interactions: hypophosphatemia associated with sucralfate in the intensive care unit

Clinically significant medication-nutrient interactions are of concern to the nutritional support practitioner. To emphasize the possible effect of the aluminum-containing medication sucralfate on serum phosphorus levels, patients admitted to the intensive care unit of a small private hospital were monitored for a 4-week period. Sixteen patients demonstrated low serum phosphorus levels; eight (50%) of these were receiving sucralfate. Eighteen patients had no low phosphorus levels measured; five (28%) patients in this group were receiving sucralfate. The hypophosphatemia observed in these patients was probably multifactorial; respiratory alkalosis and dextrose feeding as well as sucralfate use are consistent with hypophosphatemia.

Influences of diet and nutrition on clinical pharmacokinetics

The human diet represents a complex and variable mixture of nutrients, many of which have the potential for altering the disposition of drugs. This review highlights progress from a number of laboratories illustrating nutrient influences on drug dispositions and actions. Emphasis is placed on nutritional effects on hepatic drug metabolism studied in humans. Data from animals have sometimes been difficult to extrapolate to humans, as illustrated by reports on the influences of starvation, dietary lipids, and ascorbic acid. From studies in healthy subjects it is now clear that a number of specific dietary factors can influence drug metabolism by the mixed function oxidase system and conjugating enzymes. These include dietary protein, cruciferous vegetables, charcoal-broiled beef containing polycyclic aromatic hydrocarbons, and methylxanthines. The effects of such dietary components have been demonstrated for only a limited number of drug substrates for these enzyme systems. Effects of food on bioavailability have been more widely studied, and depend greatly upon the type of drug. Malnutrition can be associated with variable but potentially important effects on the bioavailability, binding, hepatic metabolism, and renal clearance of drugs. In malnourished patients it is generally difficult to recognise the roles of individual nutrient deficiencies on drug disposition, and clinical predictors of altered pharmacokinetics for various drugs in such patients are not well defined. It is likely that many important interrelationships between nutrition and new or already marketed drugs remain to be recognised, and therefore warrant further research. Nutritional effects on drug metabolising enzymes also have implications for endogenous substances such as hormones and environmental toxins and carcinogens which are metabolised by the same or related enzyme systems, and for diseases likely to be related to the actions of such chemicals.

Assessing the Nutrition Support Team

The development of clinical nutrition in the past few years has occasioned a rapid proliferation of hundreds of nutrition support teams across the country. Data available in several surveys of these teams suggest that they are so likely to differ from one another that they scarcely merit a common name. Some standard is clearly needed. A formulation of the essential features that should be found in every NST is presented. In light of this conceptual framework, data on the efficacy of NSTs are discussed. It is suggested that, although there is enough favorable evidence in cost-effectiveness for a hospital to establish an NST, the full potential of the NST as the proper repositor of a new branch of medicine (Clinical Nutrition) has yet to be widely recognized and properly tested.

Drugs and nutrition in old age

Drug effects are influenced by physiologic and pathologic changes that occur as a consequence of aging. The elderly may be more disposed to drug-induced nutrient depletion because of chronic illness, inadequate diet and long-term drug use. Digoxin, isoniazid, corticosteroids, diuretics and psychoactive agents pose special hazards to the nutritional status of elderly patients. On the other hand, dietary factors, such as protein levels or vitamin deficiencies, may be important determinants of age-related changes in drug disposition or toxicity.

Nutritional consequences of drugs used in pediatrics

Pediatric drugs may have significant nutritional consequences via their effects on appetite, nutrient absorption, nutrient metabolism, and nutrient excretion. Examples of common drugs and effects on nutrition include the inhibition of vitamin C storage by aspirin; impairment of folic acid utilization by phenobarbital; phenylalanine accumulation by trimethoprim; and lipolysis caused by caffeine. Nutritional consequences of drugs are of greater clinical significance in children who are malnourished and in those on drugs for prolonged periods. It is important that physicians consider possible deleterious consequences of drugs in making therapeutic choices.

Implications of nutritional status on human biochemistry, physiology, and health

Optimum nutrition is the level of intake that should promote the highest level of health. Although excess caloric intake will lead to obesity, a deficit in nutrition may result in a tissue depletion of essential nutrients that can lead to biochemical changes and eventually to clinical signs and symptoms. Nutrition requirements may differ according to sex, age, activity, or physiological state and can be influenced by drugs, smoking, alcohol, and other factors. With ever-increasing sedentary life styles and less physically demanding jobs, the resulting reduced caloric requirements have made it more difficult to make nutritionally sound food choices. Nutrition is the single most important component of preventive health care. Diet has been associated with cancer, heart disease, diabetes, stroke and hypertension, arteriosclerosis, and cirrhosis of the liver. The ability of the human to respond to stresses, such as altitude, heat, trauma, surgery, and infection can be influenced by nutritional status. Nutritional status is reflected in a variety of metabolic processes that provide the basis for a number of methods for its assessment.

Nutritional Assessment

An abundant food supply has brought with it problems of overnutrition in Australia, but has not precluded problems of undernutrition and, indeed, overnutrition and undernutrition may coexist. "Dysnutrition" accounts for, or is associated with considerable morbidity and mortality in Australia. Nutritional assessment, therefore, is as important as other components of patient assessment. The approaches to nutritional assessment include: (i) identification of the individual at risk; (ii) eliciting relevant symptoms and signs; (iii) ascertaining to patients' food and nutrition knowledge and beliefs; (iv) establishing recent and remote food intake patterns: (v) anthropometry; and (vi) various laboratory investigations. The early recognition of excessive adiposity is likely to be a valuable contribution to preventive medicine. In hospital practice, the early recognition of protein energy malnutrition is likely to reduce the duration of hospital stay and morbidity and mortality rates.