[NUTRITN 580] - Midterm Exam Guide - Ultimate 21 pages long Study Guide!

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UMASS-Amherst
NUTRITN 580
MIDTERM EXAM
STUDY GUIDE
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Food-Drug Interactions
Foods can affect drug therapy AND drugs can affect food and nutritional status
Some interventions involve food components, whereas others involve specific nutrients
Routes of Drug Administration
Enteral Drug Administration - uses GI tract or “gut”
oOrally or “PO” ! tablets, capsules, liquid (“PO” = By Mouth)
oRectally: suppositories used when upper GI tract is not functioning well
Parenteral Drug Administration (PN): circumvents the gut ! bypassing the usual process of eating
oSubcutaneously (SC, SQ, or subq.) injection in the fat layer, underneath the skin
Insulin, Morphine, Vaccines
Drugs administered below the epidermis
oIntravenously (IV)
Drugs administered into a blood vein
oIntramuscularly (IM)
Drugs administered into the muscle
oSublingual (SL): under the tongue
Nitroglycerin (angina)
Hyoscyamine (IBS)
oIntrathecally (spinal cord)
Methotrexate, Gentamicin, Vancomycin, Hydrocortisone
oIntradermally:
Injection into the dermal skin layer — ppd for TB between skin layers
PPD=purified protein derivate ! skin test to diagnose silent (latent) tuberculosis (TB)
oTopical
Creams, hormonal contraceptives
May work locally or may be absorbed and exert systematic effects
oInhalation/Nasal Sprays
Bronchodilators, PTH, vitamin B12, insulin
Factors that Influence the Risk of FDIs
Polypharmacy: the risk of a food-drug interaction increases with the number of medications taken
oPolydrug Use: when patients on > 5 drugs/day for a long time are especially high risk (especially elderly)
Examples: metformin, glipizide, thyroxine, Lipitor, diovan, fluoxetine
Age: elderly is more likely to be taking many drugs (both prescription and OTC medications)
oOTC: over the counter medications
oBody changes related to aging alter drug metabolism
Reduced LBM
Altered renal and liver function
oDietary changes (prescribed or self-imposed) increase risk of FDI
oAdverse FDI occur 2 to 3 times more often in elderly persons than in young adults
Gender: women usually have more fat, which alters drug distribution
Genetics: affect drug metabolism — > Many polymorphisms in drug-metabolizing enzymes
Nutritional Status: poor protein status alters binding & Special Diets
General Physical Condition: Altered GI function
Body Weight Composition: Drugs accumulate in the fat
Pregnancy/Infancy/Childhood: Drugs are not tested on pg. women & fetus (immature enzyme function in infants)
oFew drugs are tested on children, so dosages are often educated guesses
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Basic Drug Metabolism
Pharmacokinetics: process describing body’s handling of drugs: absorption, distribution, metabolism,
elimination
Absorption: movement of the drug from the site of administration into the bloodstream
oDrug absorption depends on many factors:
The route of administration
Particle size of the medication ! usually, the smaller the drug after disintegration, the more soluble
The chemistry of the drug & its ability to cross biological membranes
The pH ! either gastric or intestinal
Presence of special transport systems
The presence or absence of food in the stomach
Elderly patients have a prolonged gastric-emptying time, SO are more at risk when drugs are
taken with meals
oBUT their gastric pH may survive and be absorbed more readily, which can also be
problematic
Distribution: occurs when the drug leaves the systematic circulation and travels to various regions of the body
oMany drugs are partially bound to serum albumin ! so that some drug is bound and some is “free”
oBound drug: does not leave the blood stream & so does not produce a pharmacologic effect
Bound drugs serve as a reservoir from which the drug is slowly released
Low albumin levels increase the pharmacologic effects of the drug because more of the drug is
free
Biotransformation: metabolism of drugs by reaction such as oxidation, reduction, hydrolysis, or conjugation
oDrugs are eliminated either unchanged or as metabolites of the original drug
oTermination of the drug’s effects occurs when the concentration of the drug at the active site falls, which
results from a combination of processes:
Redistribution to other areas of the body
Biotransformation to inactive metabolites
o Enzymes called cytochrome P450’s catalyze the metabolism (mainly oxidation & reduction) of a wide
variety of drugs and other substances
Located in the liver (mitochondria & smooth endoplasmic reticulum) & other tissues (lungs & gut)
If the enzyme is not working it builds up over time
A compound in grapefruit interacts with the gut and interacts with drugs such as viagra, Xanax,
valium, statins,
oMetabolism Occurs in 2 Phases
Phase 1 Reaction: Oxidation, reduction, or hydrolysis to intermediate metabolites
Phase 2 Reactions: metabolites undergo further changes to yield more water-soluble compounds for
urinary excretion from the body
Involves the addition of water-soluble functional group
oDietary factors can alter P450 activity
St. John’s wort (an herb used to treat {tx.} depression) induces some P450 enzymes — this increases
drug metabolism and reduces the clinical effectiveness of many drugs
A compound in grapefruit/juice inhibits expression of P450 enzyme in the gut that is
responsible for metabolizing many oral medication (lasts 24-72 hours)
• Excretion of Drugs & Drug Metabolites
Renal Excretion: the major route for most drugs and metabolites
Excretion is controlled by many factors, including protein or fiber content of the diet & urinary pH
Ionized form of a drug is more water-soluble & more readily excreted
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