di pt2

• Effects of selected dietary components on drugs

  • Vitamin K-rich foods
  • K-rich foods & supplements
  • High protein meal
  • Tyramine-rich foods
  • Calcium-rich foods
  • Fibre-rich foods
• Effects of selected herbs/ dietary supplements on drugs


  • St. John's Wort (Hypericum perforatum)
  • Garlic
  • Vitamin E
  • Ginseng
  • Ginkgo Biloba
  • Aloe vera
• Vitamin K


  Fat soluble, needed for blood clotting & other important processes

  
• Warfarin


  An anti-coagulant that inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX & X)

  
• Higher level of Vit. K

  Reduces effectiveness of warfarin

  
• Potassium


  A mineral that plays a role in many body functions such as transmission of nerve signals, muscle contractions, fluid balance, and various chemical reactions
• 1. rich foods


  • White beans
  • Dark leafy greens
  • Baked potatoes (with skin)
  • Dried apricots
  • Baked a corn squash
  • Yogurt (plain, skim/ non fat)
  • Fish
  • Avocados
  • Mushrooms
  • Bananas

  
• ACE-I, K-sparing diuretics & angiotensin-R antagonists (hypertension & CVS disorders)


  Can cause retention or accumulation of K

  
• Concomitant ingestion of K-rich food should be in moderation to avoid risk of hyperkalaemia

  
• Proteins


  An essential nutrient that promotes growth, strength, energy, weight loss etc.
• High-protein food sources


  • Turkey breast (…chicken breast)
  • Fish (tuna, salmon, halibut)
  • Cheese (non-fat mozzarella)
  • Lean beef and veal (low fat)
  • Tofu
  • Beans (mature soybeans)
  • Eggs (esp. white eggs)
  • Yogurt, milk & soymilk
  • Nuts & seeds (pumpkin, watermelon seeds, peanuts, almonds)

  
• Levodopa (drugs for PD)


  Not recommended to be taken together with high-protein meals as it can reduce the cerebral uptake of levodopa
• Transportation of levodopa

  1. Levodopa is absorbed from the small intestine via a large NAA active transporter & therefore competes with dietary proteins for absorption

  2. A similar transport system transfers levodopa across the BBB

  3. Levodopa is extensively decarboxylated to DA in peripheral tissues - gut wall, liver, kidney

  4. This reduces the amount of levodopa that reaches the brain to about 1% of an oral dose, while the peripheral DA that is generated, produces unwanted effects

  5. To minimise peripheral metabolism, concomitant with DOPA decarboxylase inhibitor (carbidopa & benserazide), do not cross the BBB

  6. hence, it has no effect on the required conversion of levodopa to DA by DOPA decarboxylase in CNS

  7. Inhibition of the peripheral metabolism of levodopa increases the amount that crosses the BBB up to 5–10% of oral dose
• Tyramine


  An amino acid that is synthesised from the essential amino acid tyrosine and regulates blood pressure by stimulating the release of the catecholamines (epinephrine, norepinephrine)
• Tyramine & MAOIs (depression)

  Cause accumulation of catecholamines, leading to increased risk hypertensive crisis, altered mental status, confusion, headache
• Tyramine & NE


  1. Tyramine is taken up into nerve terminals by NET & causes the release of NE (catecholamine)

  2. MAO present in nerve terminals metabolizes cytosolic amines NE & tyramine to inactive metabolites

  3. The bioavailability of dietary tyramine (red wine & cheese) is relatively low due to the high [MAO] in GIT & liver

  4. Effects of tyramine are increased in the presence of MAOIs

  5. When MAO is inhibited, high levels of tyramine can be absorbed, resulting in increased indirect NE release, at the nerve terminal

  6. Leads to "hypertensive crisis"

  
• Calcium


  An important mineral in diet that is essential for bone development & functions, facilitates blood clot, muscle contraction & heart functions
• Calcium-rich foods


  • dark leafy greens, low-fat cheese (mozzarella), low-fat milk & yogurt, chinese cabbage (pak-choi), fortified soy-products (tofu), okra (cooked), broccoli, green snap beans, almonds, can-fish (sardines, in oil, with bones)

  
• Calcium-containing drugs


  Interactions mostly involve chelation with tetracycline & quinolones (antibiotics), bisphosphonates (osteoporosis) - resulting in reduced drug absorption, high risk of therapeutic failure
• Chelation formation by tetracycline

  1. Stable chelate complex are formed by tetracycline with chelator Ca, Mg, Fe3+ - chelation product is usually water-insoluble

  2. Ca-tetracycline chelate gets deposited in developing teeth & bones

  3. Tetracycline is distributed in breast milk & readily cross trough the placental barrier - causes temporary suppression of bone growth & permanent tooth staining (mid pregnancy à 4-5m of postnatal, anterior deciduous teeth & few months – 5y, anterior permanent teeth)

  
• Significant SE of Ca-tetracycline chelate


  • Incorporation into tissues that are calcifying at the time of their administration - teeth, cartilage & bone, resulting in permanent discoloration of primary & permanent dentitions
  • Depends on dosage used, length of treatment or exposure, stage of tooth mineralization / calcification & degree of activity of the mineralization process
  • During eruption of teeth, it causes the yellow / grey discoloration of teeth
  • Upon exposure to light, it is oxidized, causing yellow to brown discoloration in months to years
• Dietary fibre or roughage


  The portion of plant-derived food that cannot be completely broken down by human digestive enzymes
• Fibre sources

  • Bran (corn)
  • Cauliflower & broccoli (raw cauliflower)
  • Cabbage
  • Berries (raspberries)
  • Leafy greens
  • Celery
  • Squash
  • Bean (kidney)
  • Mushrooms (cooked white mushrooms)
  • Oranges (all varieties)

  
• Fibre consumption with drug for CHF like digoxin

  Not advisable due to its effect on reduced drug bioavailability
• Herbs


  Plants with savoury or aromatic properties that are used for flavouring & garnishing food, medicinal purposes, or for fragrances (excluding vegetables & other plants consumed for macronutrients)
• Spices


  Usually dried & produced from other parts of the plant, including seeds, bark, roots, fruits
• Dietary supplements


  Products taken orally that contain ≥1 ingredients (vitamins or amino acids) that are intended to supplement one's diet & are not considered food
• St. John Wort


  Considered a metabolic enzyme inducer – can reduce the concentration of medications in the blood
• St. John Wort


  Specifically it reduces drug concentrations of digoxin (for heart failure), lovastatin (for lowering cholesterol), viagra (for treatment of erectile dysfunction)
• Garlic (allium sativa)


  Produces a chemical called allicin, most commonly used for conditions related to the heart & blood system including high blood pressure, high levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia), hardening of the arteries (atherosclerosis)
• Garlic


  Increases the metabolism of oestrogen, reduces the effectiveness of oral contraceptive pills
• Vitamin E


  A vitamin that dissolves in fat, found in many foods including vegetable oils, cereals, meat, poultry, eggs, fruits, vegetables, wheatgerm oil
• Concomitant use of warfarin (anti-coagulant) & Vitamin E

  Increases anti-coagulation activity by inhibiting the synthesis of vitamin-K clotting factors, increased risk of bleeding

  
• Ginseng


  2 main types: Asian or Korean ginseng (Panax ginseng) and American ginseng (Panax quinquefolius)
• Ginseng


  Interferes with warfarin, aspirin, heparin, NSAIDs, increased risk of bleeding
• Aspirin


  In-vivo is reported to alter the iron uptake from the GIT, this effect coupled with acute or chronic blood loss due to GIT erosion induced by aspirin is believed to cause iron-deficiency anemia in humans
• Ginkgo biloba


  A large tree with fan – shaped leaves, native to China, Japan, Korea, contains high levels of flavonoids & terpenoids, antioxidants that provide protection against oxidative cell damage from harmful free radicals – believed to help reduce the risk of cancer
• Aloe vera


  A short-stemmed shrub, the leaves of aloe vera are succulent, erect, form a dense rosette, widely used in food, cosmetics, food supplements, herbal remedies
• Aloe vera


  • Increased risk of hypoglycaemia when combined with diabetes drugs like glyburide
  • Can decrease potassium levels, increasing risk of hypokalaemia when combined with digoxin & diuretics