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Part II Nutrition Assessment, Consequences, and Implications

histamine, and other pressor amines before they reach the systemic circulation. MAOIs block MAO activity, increasing the concentration of unoxidized pressor amines, such as tyramine, in the body. The inhibition of MAO by the MAOIs tranylcypromine (Parnate), phenelzine (Nardil), and isocarboxazid (Marplan) prevents the breakdown of tyramine, dopamine, or other pressor agents in foods such as aged cheeses or meats. The presence of these unoxidized pressor amines causes constriction of the blood vessels, which results in abnormal elevation of blood pres- sure, headaches, mood elevations, and possible death. When a drug with known MAOI activity is taken, foods high in pressor amines such as tyramine need to be avoided. Table 17.3 lists food supplements and drug interactions (see pages 248–249); Table 17.4 addresses common biochemical abnormalities associ- ated with medications prescribed for enterally fed patients (see page 250).

Alcohol

Many health care professionals overlook alcohol as a drug. The National Survey on Drug Use and Health conducted in 2010 found that nearly 40% of adults 65 and older drink alcohol (19). Unfortunately, many of these individuals may not consider the effect that alcohol can have on nutritional status and on medica- tions. Older adults have a lower tolerance for alcohol because they metabolize it more slowly as a result of having lower total body water; therefore, the blood alcohol becomes more concentrated in older adults. Nutritional assessment of the older adult suffering from alcoholism is a challenging task no matter the setting (eg, community, assisted living, nursing facility). Clinical signs and symptoms of alcohol-related malnu- trition are dependent on the stage of alcoholism, the level of socioeconomic integration, social and familial networks, alcohol- and nonalcohol-related conditions/ diseases (especially liver disease), and medication intake.

Alcohol interacts with most antidepressants, antibiot- ics, anticoagulants, and other drugs used for neurological benefits. It may also increase the GI irritation caused by medications such as aspirin or other nonsteroidal anti- inflammatory drugs (eg, ibuprofen). Chronic use of ethanol may increase the hepatotoxicity of medications such as acetaminophen or isoniazid.

Ethanol can also inhibit gluconeogenesis, thus prolonging a hypoglycemic episode induced by insulin or oral hypoglycemic agents (eg, glyburide [DiaBeta or Micronase]). In addition, the combination of disulfiram (Antabuse) and ethanol produces a potentially life-threatening reaction characterized by flushing,

rapid heartbeat, palpitations, and elevation of blood pressure.

Alcohol may also affect several nutrients.

Wernicke-Korsakoff syndrome, one consequence of long-term alcohol abuse, is associated with thiamin deficiency (20). Alcoholism is often connected to increased fracture risk, possibly due to the effects on vitamin D metabolism (21,22). The metabolism of all water-soluble vitamins may be affected by the con- sumption of alcohol. RDNs must pay closer attention to intakes of thiamin, riboflavin, niacin, vitamin B-6, folic acid, and vitamin C. In addition, increased iron absorption and decreased magnesium and zinc absorp- tion may occur (20).

Because alcohol is distributed throughout the body and is able to cross all membrane barriers, it is very likely to interact with a drug’s mechanism of action. For all medications, the RDN should review warnings to restrict or avoid alcohol and also be aware of the alcohol content within some drugs.

Caffeine Caffeine, depending on the amount consumed, can have differing effects on the central nervous system, cardio- vascular system, and metabolism. Symptoms can include a sense of alertness, decreased fatigue, and clear thinking when lower doses are consumed, but higher doses can cause tremors, restlessness, irritability, ner- vousness, and insomnia. In even higher doses, seizures and cardiovascular instability may occur. Caffeine should be avoided when taking certain antimicrobials and antibiotics as well as most antianxi- ety drugs. Caffeine-containing products should be avoided when taking drugs used to control gastro- esophageal reflux (heartburn), beta-blockers, or bron- chodilators. When limiting caffeine in the diet, it is important to consider OTC medications that may be high in caffeine such as appetite suppressants, caffeine pills, analgesics, and allergy/cold relief tablets. Box 17.5 outlines the drug-nutrient interaction issues asso- ciated with caffeine, as well as signs and symptoms of clinical excesses and withdrawal (23).

Grapefruit Juice

“Grapefruit juice and grapefruit product consumption have potential health benefits; however, intake is also associated with interactions with certain drugs, includ- ing calcium channel blockers, [antihyperlipidemics (HMG-CoA reductase inhibitors),] immunosuppres- sants, and antihistamines.” Citrus fruits such as grape- fruits, tangelos, limes, Seville oranges, and pomelos contain active ingredients that irreversibly block the drug metabolizing enzyme cytochrome P450 3A4. These foods inhibit metabolism of some drugs such as