Nutrition and Oral Medicine (Nutrition and Health)

94 Part II / Oral and General Healthand cimetidine [17]) drugs, causing increased drug concentrations that can lead to displacementof nutrients from plasma proteins or tissue-binding sites. This can lead toincreased excretion of the affected nutrient, either free or in drug–nutrient complexes.Drugs used to treat chronic diseases can also lead to increased nutrient requirements.For example, select drugs such as sulfasalzine (Azulfadine), INH, and methotrexatecontribute to folic acid deficiencies in patients with inflammatory bowel disease,tuberculosis, and rheumatoid arthritis (8). Individuals with end-stage renal disease maydevelop deficiencies in riboflavin, vitamin C, and folic acid if they are not givensupplemental doses of these nutrients because of the nature of the disease and use ofdiuretics and dialysis. Patients with chronic renal disease also have impaired absorptionof calcium secondary to decrease in renal production of 1,25-dihydrocholecalciferol.Intestinal enzymes such as pepsinogen, amylase, and lipase, which help to digest foodand bacteria are needed to help absorb vitamins B 1 , B 2 , B 6 , B 12 , and vitamin K. Malabsorptionof these nutrients can be caused by drugs that kill off these bacteria, such asbroad-spectrum antibiotics, or drugs that damage the lining of the intestines, thus reducingabsorption and enzyme action (1). Table 3 summarizes the clinical manifestations ofspecific vitamin deficiencies.4. DRUGS AND FOOD INTAKEDrugs can affect appetite as well as GI function, resulting in alterations in food intake.Drugs affecting appetite may have either a central or peripheral effect. Some drugs suchas antidepressants and prednisone may increase appetite and cause weight gain, whereasothers such as chemotherapeutic agents contribute to weight loss by causing anorexia,nausea, and vomiting. Many drugs (see Table 1) have oral side effects such as xerostomiaor stomatitis that can affect food intake. A wide variety of drugs can cause changesin taste or smell alterations. Potassium iodide is secreted into the saliva, producing aconstant unpleasant taste that is difficult to eradicate. Chlorpromazine and metronidazolecause a persistent metallic taste that inhibits food intake. Penicillamine causes zincdepletion, leading to loss of taste and loss of desire for food (18). Digitalis, especiallyin patients with decreased renal function, can cause marked nausea and vomiting.Biguanides, used as oral hypoglycemic agents, cause impaired appetite and decreasedfood intake. Chemotherapy drugs, especially cisplatin, actinomycin D, adriamycin,dacarbazine, streptozocin, nitrosoureas, nitrogen mustard, and cyclophosphamide, andfolic acid analogs (19) induce nausea, vomiting, anorexia, and subsequent weight loss.In patients who may have marginal intake of required nutrients, drugs causing anorexiacan result in nutritional deficiencies.5. FOOD AND DRUG INTERACTIONSAbsorption of drugs may be decreased or more infrequently increased by the presenceof food, which changes the pH, osmolality, secretions and motility of the gastrointestinaltract (Table 2) (9). Drug bioavailability may be affected by direct interactions betweenthe drug and food, such the formation of drug–protein complexes or chelation withpolyvalent metal ions (20). For example, tetracycline forms an insoluble complex withcalcium, rendering it ineffective when taken with dairy products (9). Food may act as a