Bovine respiratory disease, the most common and costly disease in the beef industry, results from complex interactions between the host, the environment, and potential pathogens. Environmental stressors play a major role in susceptibility to and transmission of disease pathogens. This module describes cost-effective preventive management measures that reduce incidence of the disease and thus the need for antimicrobial treatment. Beef practitioners play an important role in promoting these preventive measures and reducing the unnecessary use of antibiotics.

1. Chapter 9
Clinical: Food-Drug Interactions

2. Importance of Awareness
 Drug–nutrient interactions: specific changes to
pharmacokinetics of a drug caused by nutrient(s) or
changes to the kinetics of nutrient(s) caused by a
drug
 Food–drug interactions: broader term that also
includes effects of medication on nutritional status
e.g. a drug causing a vitamin deficiency
 Food–drug interactions can
 Alter the intended response to medication
 Cause drug toxicity
 Alter nutritional status

3. Benefits of Minimizing Drug
Interactions
 Medications achieve intended effects
 Patients do not discontinue drugs
 Minimize need for additional medication
 Avoid adverse side effects
 Preserve optimal nutritional status
 Avoid accidents and injuries
 Minimize disease complications
 Reduce cost of health care services
 Meet licensing agency requirements

4. Pharmacologic Aspects
 Pharmacodynamics: physiologic and biochemical effects of a
drug or combination of drugs
 Pharmacokinetics: movement of a drug through the body by
absorption, distribution, metabolism, and excretion
 Process:
 Absorption: from site of administration to the bloodstream
 Distribution: from blood to other regions of the body
 Bound vs. unbound fraction: only unbound fraction can effect target
organ
 Biotransformation: metabolism- the major organ is the liver
 Cytochrome P-450 enzyme system: An important enzyme system in the
liver that facilitates drug metabolism
 Excretion: elimination of drugs and their metabolites

5. Risk Factors for Food–Drug
Interactions
 Polypharmacy: taking many drugs
 Chronic disease
 Older patients
 Malnutrition – affects albumin levels
 Cancer and AIDS
 GI tract alterations- nausea, vomiting, diarrhea, anorexia
 Body composition- accumulation of fat-soluble drugs
 Fetus, infant, pregnant woman- drugs not tested on unborn-
pregnant women need to avoid many drugs

6. Effects of Food on Drug Therapy
1. Drug absorption
 Bioavailability
 Meds delivered via IV are 100% bioavailable but decreases when
consumed orally because of incomplete absorption and
metabolism (due to e.g. fiber, fat, and other food components). If
food in the stomach is a major issue, the drug will come with
directions on meal timing.
 GI pH: Any situations that results in a change in gastric pH such as
achlorhydria or hypochlorhydria can reduce drug absorption.
 E.g. failure of ketoconazole to clear candida in patients with HIV when patient
also on acid-reducing agent for GERD

7. Effects of Food on Drug Therapy
2. Drug distribution
 Albumin is the most important drug-binding protein in the blood. Low
serum albumin levels (poor intake for any reason) eventually means there
are fewer drug binding sites leading to more unbound drug circulating
through the body. Treatment: lower dosing of some medications
3. Drug metabolism
 Enzyme systems in the GI tract and liver account for much of the drug
metabolism in the body. Food can both inhibit or, enhance drug metabolism
by changing the activity of these enzyme systems
 E.g. a substance found in grapefruit and grapefruit juice can inhibit the intestinal
metabolism of some drugs and VERY IMPORTANTLY, grapefruit and grapefruit juice
inhibits the cytochrome P- 450 which is responsible for the metabolism of many oral
drugs including statins prescribed for high serum cholesterol. Normal metabolism
cannot be completed so more unmetabolized drug remains in systemic circulation
resulting in potential toxicity.
 Patients must avoid grapefruit altogether (not enough to separate from drug
administration)

8. Effects of Food on Drug Therapy
4. Drug excretion
 Some food and nutrients can alter the reabsorption of drugs
from the renal tubules
 The drug lithium is resorbed by the kidneys as part of normal
metabolism; when lithium is resorbed, so too is Na. When a
patient consumed too much Na, the kidneys work to eventually
excrete this sodium, unfortunately lithium follows suite and is also
excreted. Patient who consume too much Na, therefore excrete a
lot of Na, excrete too much lithium thus decreasing it’s
therapeutic effects.

9. Effects of Drugs on Food and Nutrition
1.Nutrient absorption
 Chelation: Can occur between medications and mineral –
reducing the amount of mineral available.
 Adsorption: Some antihyperlipidemic bile acid sequesterants
cause fat-soluble vitamin malabsorption
 Transit time: Some drugs speed up transit time so not enough
digestion can occur
 GI environment: pH
 Damage intestinal mucosa: These drugs have the greatest effect
on nutrient absorption. Damaging the villi and microvilli inhobits
the brush-border enzymes and intestinal transport systems the
body uses to get nutrients from the GI tract to circulation
(NSAIDS!)

10. Effects of Drugs on Food and Nutrition
2. Nutrient metabolism
A drug may increase speed of metabolism
Vitamin antagonism: because of a drug a vitamin cannot be
converted to its active form. E.g. anticonvulsants
(phenobarbotol) increase metabolism of vits D, K and B9 (folic
acid)
3. Nutrient excretion
 Interfere with nutrient resorption
 Increase or decrease excretion

11. Effects of Drugs on Nutritional Status
 Side effects
 Oral, taste, and smell
 Dysgeusia (taste distortion) and hypogeusia (reduced ability to taste)
 Metallic or salty taste
 Antineoplastic drugs (for tumors): mucositis (inflammation of mucosal lining
of GI tract)
 Xerostomia (dry mouth)
 GI effects
 Irritation and ulceration
 Nausea and vomiting
 Constipation or diarrhea
 Destruction of intestinal bacteria
 Fat malabsorption

12. Effects of Drugs on Nutritional Status
(cont’d)
 Appetite changes
 Undesired weight changes
 Nutritional imbalance
 Growth retardation in children
 Appetite suppressants
 Stimulant drugs and hypertension
 CNS side effects
 Appetite stimulants: undesirable and desirable

13. Excipients and Food–Drug Interactions
 Excipients: inactive ingredients added as buffers, binders,
fillers, diluents, flavorings, dyes, preservatives, suspending
agents, or coatings
 Allergies and enzyme deficiencies
 Lactose
 Gluten sensitivity
 Nutritionally significant amounts of excipient nutrients

14. Medical Nutrition Therapy for
Food–Drug Interactions
 Prospective: all medical nutrition therapy 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
 Diet history: include OTC, alcohol, supplements, and herbals
 Warnings and recommendations