Transcript chp 19 Krause

Chapter 19
Food-Drug
Interactions
Key Terms

Bioavailability: degree to which a drug or
other substance reaches the circulation and
becomes available to the target organ or tissue

Drug-nutrient interactions: the results of the
action between a drug and a nutrient that would
not happen with the nutrient or drug alone
© 2004, 2002 Elsevier Inc. All rights reserved.
Key Terms—cont’d

Half-life: amount of time it takes for the blood
concentration of a drug to decrease by one half
of its steady state level

Side effect: adverse effect/reaction or any
undesirable effect of a drug
© 2004, 2002 Elsevier Inc. All rights reserved.
Pharmacology Terms
Stages of Drug Action

Pharmacokinetics: movement of a drug
through the body by absorption, distribution,
metabolism, and excretion

Pharmacodynamics: physiologic and
biochemical effects of a drug or combination of
drugs
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Pharmacology Terms—cont’d

Pharmacogenomics: genetically determined
variations that are revealed solely by the effects
of drugs
© 2004, 2002 Elsevier Inc. All rights reserved.
Therapeutic Importance

Therapeutically important interactions are
those that:
—Alter the intended response to the
medication
—Cause drug toxicity
—Alter normal nutritional status
© 2004, 2002 Elsevier Inc. All rights reserved.
Other Terms

Bioavailability: % free to function

Absorption rate: % absorbed and time for
absorption

Transported: amount in blood (free or bound)

Metabolized: altered by enzymes in tissues

Mixed-function oxidase system (MFOS):
enzyme system that metabolizes drugs,
carcinogens, compounds in foods, etc.
© 2004, 2002 Elsevier Inc. All rights reserved.
Patients at Risk for Food-Nutrient
Interactions

Patient with chronic disease

Elderly

Fetus

Infant

Pregnant woman

Malnourished patient
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Drug Effects on Nutrition

Decreased or increased intake
—Appetite
—Taste
—Nausea
—Dry mouth

Alter metabolism
—Anti-vitamins
—Monoamine oxidase inhibitors
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Drug Effects on Nutrition—cont’d

Change absorption
—GI pH
—Transit time or motility
—Bile acid secretion or activity
—Drug-nutrient complexes
—Muscosal damage

Change excretion
© 2004, 2002 Elsevier Inc. All rights reserved.
Nutrient Effects on Drugs

Absorption
—Note if drug is taken with or without food
—Note which foods to avoid

Metabolism
—Changes in diet may alter drug action
—Malnutrition alters albumin level (blood
binding) and MFOS enzyme activity
level
© 2004, 2002 Elsevier Inc. All rights reserved.
Nutrient Effects on Drugs—cont’d

Excretion
—Fluid status
—Urinary pH
© 2004, 2002 Elsevier Inc. All rights reserved.
Important Interactions

Oral contraceptives
—Folate

Antihypertensives
—Ca
—K
—Mg

MAOIs
—Tyramine in foods
© 2004, 2002 Elsevier Inc. All rights reserved.
Key Information
1. Physician’s Desk Reference – food and drug
interactions—there are other drug indexes
2. Generic or chemical name differs from brand
name
3. Drugs are classified by action, manufacturer,
class, brand name, and generic name
4. Over-the-counter drugs may be bought without
prescription
© 2004, 2002 Elsevier Inc. All rights reserved.
Examples of Drug Categories That
May Cause Loss of Appetite

Antiinfectives

Antineoplastics

Bronchodilators

Cardiovascular drugs

Stimulants
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Examples of Drug Classes That
Cause Diarrhea

Laxatives

Antiretrovirals

Antibiotics

Antineoplastics
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Drugs That May Increase Appetite

Anticonvulsants

Hormones

Psychotropic drugs
—Antipsychotics
—Antidepressants, tricyclics, MAOIs
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Drugs That May Affect
Glucose Levels

Antidiabetic drugs

Drugs that can cause hypoglycemia

Antiretrovirals, protease inhibitors

Diuretics, antihypertensives

Hormones
© 2004, 2002 Elsevier Inc. All rights reserved.
Medical Nutrition Therapy for
Food-Drug Interactions

Prospective: all MNT offered when the
patient first starts a drug

Retrospective: evaluation of symptoms to
determine if medical problems might be
the result of food-drug interactions
© 2004, 2002 Elsevier Inc. All rights reserved.
Enteral Nutrition and Drugs

Drugs put in feeding tubes may cause:
—Diarrhea
—Drug-nutrient binding
—Blocked tube

Avoid adding drug to formula

When drugs must be given through tube:
—Stop feeding, flush tube, give drug, flush
—Use liquid form of drug
—Avoid crushing tablets
© 2004, 2002 Elsevier Inc. All rights reserved.
Summary

All drugs are metabolized ahead of
nutrients.

Most drugs have nutritional status side
effects.

Always look for potential interactions.

Watch for use of multiple drugs
(polypharmacy) especially among the
elderly!
© 2004, 2002 Elsevier Inc. All rights reserved.