Page 1147 - Small Animal Clinical Nutrition 5th Edition

Chapter
69

VetBooks.ir

Effects of Food on

Pharmacokinetics

Martin J. Fettman
Butch KuKanich
Robert W. Phillips

“Give me a lever long enough and a fulcrum on which to place it,
and I shall move the world.”
Archimedes

ing, precipitation, inactivation or ionization, which alter gas-
INTRODUCTION
trointestinal (GI) absorption. These interactions may occur
When the effects of veterinary pharmaceuticals are evaluated in vitro after mixing the drug with food to make administra-
and standardized doses are determined, researchers typically tion more convenient, to enhance palatability or to reduce GI
use relatively healthy, fasted animals that have been maintained irritation. Another concern is adsorption of drugs to synthet-
on foods with acceptable nutrient balance. However, in clinical ic surfaces of the equipment used for nutrient and drug
settings, animals receiving a drug often have variable food administration (e.g., food containers, feeding syringes and
intake or specific nutrient imbalances, or they must be given a tubing for assisted feeding). Physiochemical interactions may
drug in conjunction with a meal, or some combination of these occur in vivo, whereby drug absorption from the GI tract is
factors may occur. The patient’s health status and the nutrient decreased because of chelation by dietary fiber or minerals, or
ingredient profile of the diet being consumed may greatly affect increased because of favorable changes in ionization or sol-
drug absorption, distribution, metabolism, elimination, efficacy vent partitioning.
and toxicity (Table 69-1). Concurrent food intake also may
markedly affect drug availability and pharmacokinetics (Tables Metabolic Interactions
69-2 and 69-3). Both nutrient and non-nutrient substances in foods can alter
Veterinarians should be acquainted with the effects diet can the metabolism of absorbed drugs. Nutrients are nourishing
have on drug disposition to anticipate adjustments in the food ingredients of food. Non-nutrient substances are chemicals
or drug dose, properly time administration of drugs and allow without metabolic value, including naturally occurring phy-
for changes in the margin for error between efficacy and toxic- tochemicals and synthetic chemicals added inadvertently or
ity of pharmaceutical agents. purposely to food. Protein and energy malnutrition can alter
the synthesis of plasma proteins, affecting drug distribution
and pharmacokinetics. Individual dietary lipid, carbohydrate,
GENERAL TYPES OF FOOD protein, vitamin and mineral levels can effect changes in
AND DRUG INTERACTIONS xenobiotic-metabolizing enzymes, resulting in altered clear-
ance, circulating concentrations and resultant therapeutic
Food-drug interactions that occur as a result of the physical efficacy and toxicity. Naturally occurring non-nutrient food
form or chemical properties of food may lead to drug bind- ingredients and added synthetic preservatives may similarly