Chapter 17 Implications of Drug-Nutrient Interaction and Pharmacology

supplements concurrently with medication are at increased risk for nutrient-induced alterations in phar- macokinetics (6). The presence of food, vitamin, mineral, and other dietary supplements has the ability to alter the pH and the osmolality of the GI tract. These changes can affect the absorption of drugs as a result of alterations in drug ionization, stability, solubility, and transit time. Food can also affect drug absorption because of physical or chemical interactions between the food and the drug itself.

DRUG-NUTRIENT INTERACTIONS AND OLDER ADULTS

Older adults are at particular jeopardy for drug-nutrient interactions. Several factors contribute to this height- ened danger, including drugs, pathological factors, geriatric factors, and nutrition.

Drug-Associated Factors

Negative outcomes from drug-nutrient or drug-drug interactions can include falls, depression, confusion, hallucinations, and malnutrition, which may result in illness, hospitalization, and death among this group of individuals. “Drug-related complications have been attributed to the use of multiple medicines and associ- ated drug interactions, age-related changes, human error, and poor medical management (eg, incorrect medicines prescribed, inappropriate doses, lack of communication, and monitoring). Almost 40% of seniors are unable to read prescription labels, and 67% are unable to understand information given to them” (3).

Other drug-associated factors contributing to increased risk of drug-nutrient interactions include the dosage, the duration, and the frequency of prescribed medications. The physical changes associated with aging could contribute to drug efficacy and, if the dosage is not adjusted, potential drug toxicity. Drug duration and frequency also need to be monitored, especially in those individuals who started drugs in middle age and have not had those drugs reviewed or adjusted since then (6).

Pathological Factors Older adults are more likely than young or middle-aged adults to have disease conditions such as cardiovascular disease, GI malabsorption, liver disease, or renal disease. The presence of these disease states may have an adverse effect on the pharmacoki- netics of a medication (14). The normal functioning of organ systems is altered in older adults, leading to changes in pharmacokinetics. As a result, drug doses must be adjusted accordingly, especially any drugs that are filtered through the kidneys (15).

Geriatric Factors

Regardless of the presence of disease states that could be risk factors for drug-induced nutrient deficiencies, certain age-related factors still put any person older than 65 years at significant risk for drug-induced nutri- tional deficiencies. Anyone older than 75 years is at even higher risk, and those over 85 years are at the greatest risk for drug-induced nutrient deficiencies (16). Age-related GI factors include reduced gastric acid secretions and gastric emptying, reduced splanch- nic (visceral) blood flow, and intestinal motility, all of which decrease the absorption of the drug (6,15). Age- related changes in the kidneys and liver affect drug metabolism and excretion. “In addition, age-related body composition changes such as increased adipose tissue and loss of skeletal muscles can impact drug dis- tribution. Furthermore, drug receptors and tissue sensi- tivity are affected by age” (6). Consequently, age-related factors contribute to alterations in drug effi- cacy and drug toxicity among older adults.

Nutrition-Related Factors An individual consuming a poor-quality diet or someone with compromised nutritional status is more likely to experience nutritional-related side effects associated with drug-nutrient interactions than a person whose nutritional status is adequate. The older adult often consumes a diet that is not adequate in energy, protein, calcium, and B vitamins and is at risk for side effects resulting from the deficiency of these nutrients (17,18).

Older adults must be assessed individually for the

effect of food on each drug’s action as well as the effect of drugs on the older adult’s nutritional status. Interactions can be caused or complicated by a variety of factors. Risk factors for food-drug interaction are listed in Box 17.1.

BOX 17.1 Risk Factors for Food-Drug Interaction

Polypharmacy Nutrition status Genetics

Underlying illness Therapeutic diet Nutrition supplements

Enteral/parenteral feeding

Herbals/phytonutrient products

Alcohol intake Drug abuse Allergies/intolerances Noncompliance Malnutrition Dehydration

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