FoodDrug Interactions

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Food-Drug Interactions

• Dr. William Diehl-Jones
• Faculty of Nursing and
• Department of Zoology

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Agenda

• Types of Food-Drug Interactions
• Effects of food on absorption
• Effects of food on metabolism
• Specific food-drug Effects

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Food-Drug Interactions

• It is primarily in two realms - pharmacokinetics,
  and pharmacotherapeutics where we can have
  Food-Drug interactions
• The interactions can be general or specific
• General
• whether a drug should be taken with or without
  food
• Specific
• whether certain drugs are specifically affected
  by specific foods

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Food-Drug Interactions That Affect Absorption

• Note We will NOT discuss
• alcohol-drug effects

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Food May Decrease Drug Absorption

• Mainly a function of food BINDING to a drug
• This can be considered a general effect
• Can either ? or ? drug absorption across the gut
• Dictates whether a drug should be taken on an
  EMPTY or FULL stomach
• Another important factor
• Whether a med irritates the GI tract
• Eg aspirin

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Drugs to be Taken on an EMPTY Stomach

• Antihistamines
• Eg Allegra, Claritin, Hismanal, Zyrtec
• Analgesics/Antipyretics
• Eg Acetominphen (Tylenol)
• Food generally DECREASES absorption
• Food will delay absorption

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Drugs to be Taken on a EMPTY Stomach

• HMG-CoA Reductase Inhibitors
• Eg statins
• Atorvastatin (Lipitor), cerivastatin (Baycol)
• Mechanism of action
• These are difficult to absorb, so advise clients
  to take with evening meal (why?)

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Drugs to be Taken on an FULL Stomach

• Analgesics/Antiinflammatories/Antipyretics
• Eg NSAIDS
• Ibuprofen (Advil, Motrin)
• Indomethacin (Indocid)
• Naproxen (Anaprox, Alleve)
• Aspirin
• These cause stomach upset food will help to
  buffer
• Aspirin irritates the stomach and increases
  gastric bleeding a buffered or enteric-coated
  form of Aspirin may be given

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Drugs to be Taken on an FULL Stomach

• Corticosteroids
• Eg
• methylprednisone
• Prednisone
• Prenisolone
• Cortisone acetate
• These drugs can cause stomach upset
• They may also cause HYPERGLYCAEMIA
• So what?

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Drugs to be taken on a FULL Stomach

• Lovastatin (Mevacor)
• A statin we will speak of shortly
• This drugs is poorly absorbed without food, so
  your client should take this with an evening meal

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So, How Can Food Affect Metabolism?
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Grapefruit Juice

• Decreases the activity of a specific cytochrome
  P450, called CYP3A3
• This means that drugs metabolized by CYP3A3
  during phase I will not be degraded as quickly
• Bottom line a greater concentration of drug
  remains in the plasma

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Grapefruit Juice

• MOST prescription drugs do NOT show
  clinically-relevant interactions
• Which drugs should you watch-out for?

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Drugs Which MayInteract with GJ

• Antihistamines
• Anti-infectives
• Benzodiazepines
• Calcium Blockers
• Cholesterol Lowering Drugs
• Immune system suppressants
• Psychiatric Drugs

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Drugs Which are Safe with GJ

• Alpraxolam
• Xanax
• Biaxin
• Digoxin
• Haloperidol

• Pracochol
• Coumadin
• Verapamil
• Itraconazole
• Dilantin

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What is active ingredient in GJ?

• Naringen
• Metabolized by enteral bacteria to NARINGENIN,
  which is a specific CYP3A4 inhibitor
• Furanocoumarins
• Also a CYP inhibitor

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Specific Food-Drug Interactions
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Bronchodilators

• These drugs are used to treat bronchial diseases
• Theophylline, Albuterol, Epinephrine
• High-fat meals may ? theophylline in body
• High carbohydrate meals may ? theophylline
• The FORM of the drug is important
• Food has NO effect on Theo-dur and Slo-Bid
• Food ? Theo-24 and Uniphyl absorption
• Food ? Theo-Dur Sprinkles absorption in children
• AVOID CAFFEINE also stimulates CNS

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While we are talking about theophylline
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Caffeine and Theophylline are Methylxanthines
Found in Coffee and Tea

• Caffeine
• Lethal dose is 10 g (100 cups)
• Withdrawal symptoms in people who routinely have
  more than 600 mg/day (6 cups)
• Theophylline
• LOTS in tea

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Diuretics

• Many different types eg
• Furosemide (Lasix)
• triamterene (Dyazide)
• Dyazide is potassium-sparing
• What does this mean?
• Patients taking Triamterene should avoid
  patassium-rich food
• Eg?
• Why?

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ACE-Inhibitors

• Again, different types
• Captopril (Capoten), moexipril (Univasc)
• The also ? the amount of potassium in the body
• So, what do you recommend?
• Also food interferes with absorption

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Anticoagulants

• Prevent blood-clot formation
• Eg Coumadin (Warfarin)
• A VITAMIN K antagonist
• So, what would you tell your client to avoid if
  s/he were on coumadin?

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Antibiotics

• Take your pick
• Penicillins, Cephalosporins, Macrolides,
  Sulfonamides, Tetracylines, Quinolones
• In general, these can cause stomach upset
• Pay attention to two in particular
• Quinolones (eg ciprofloxacin)
• Tetracyclines (eg vibramycin, minocin)
• AVOID calcium-containing foods, minerals containg
  iron and antacids (they decrease drug
  concentration)

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Also Avoid Dairy With This

• Antifungal agents
• Fluconazole (Diflucan)
• Griseofulvin (Grifulvin)
• Ketoconazole (Nizoral)
• Again, dairy products inhibit absorption

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MAO Inhibitors

• These are a very powerful group of drugs which
  are used in the treatment of depression and
  anxiety disorder
• MANY DIETARY RESTRICTIONS
• If taken with foods high in TYRAMINE, a rapid,
  fatal increase in blood pressure may occur .

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So, what foods are high in TYRAMINE?

• Proceesed cheese, cheddar, brie, mozarella,
  parmesan cheeses, yogurt, sour cream
• Beef or chicken liver, cured meats such as
  sausage and salami, game meat, caviar, dried fish
• Avocados, bananas, yeast extracts, rasins,
  sauerkraut, soy sauce, miso soup
• Broad (fava) beans, ginseng, caffeine

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Anti-Anxiety Drugs

• Benzidiazapenes
• Eg Lorazepam (Ativan), Diazapm (Valium),
  alprazolam (Xanax)
• Clients should avoid CAFFEINE
• May increase excitability, lessen therapeutic
  effects

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The Bottom Line

• ASK what meds your clients are on
• CHECK each med for possible food-drug
  interactions
• A handy resource is the CPS
• Another handy resource is your pharmacist
• Remember to ask about herbal supplements
• RECOMMEND alternatives

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Some Useful Resources

• http//powernetdesign.com/grapefruit/general/GJDIs
  ummary.pdf
• http//www.foodmedinteractions.com
• Pharmacotherapy A Pathophysiologic Approach 6th
  Ed. DiPrio et al, 2005
• I may be contacted via email if you would like
  clarification/additional information
• Bill_Diehl-Jones_at_umanitoba.ca