Nutrition and Oral Medicine (Nutrition and Health)

96 Part II / Oral and General Healthciprofloxacin (Cipro), ofloxacin (Floxin), and enoxacine (Penetrax), causing reducedabsorption and blood levels (21). Fluid intake may affect how well water-soluble drugsare absorbed. Excessive consumption of foods rich in vitamin K can alter prothrombintimes in patients on coumadin. Patients taking coumadin do not have to avoid foods highin vitamin K, such as liver, broccoli, brussel sprouts, and green leafy vegetables (e.g.,spinach, Swiss chard, coriander, collards, cabbage), but it is important that the patientkeep his or her intake consistent so that the amount of vitamin K eaten remains the same.Certain foods can affect the rate of drug metabolism or elimination. Grapefruit juice,even consumed 24 h before taking certain drugs, can inhibit an intestinal enzyme necessaryfor drug breakdown, resulting in a more potent drug effect. Examples of these drugsinclude carbamazepine (Tegretol), amiodizine (Norvasc), nifedepine (Procardia),felodipine (Plendil), cisapride (Propulsid) (22), and atorvastatin (Lipitor). Foods canaffect the rate of elimination of a drug by changing the pH of the urine. If the pH of theurine is modified, it is possible that there will be prolonged effects of a drug by increasingthe un-ionized form in the urine (favoring reabsorption) or expedited elimination bypromoting the excretion of the ionized form. If the urine has a low pH, weakly basic drugssuch as amitriptyline and chloroquine are excreted, because they form water-soluble salts(4). Foods that can cause acidification of the urine include meat, fish, chicken, seafood,eggs, cheese, peanut butter, and most processed carbohydrates such as breads and pasta.Conversely, the action of some drugs is prolonged if the pH of the urine is high becausethere is decreased ionization and therefore reduced elimination and increased absorptionby the kidneys. Low protein diets, chronic antacid use, citrus fruits, milk products, andmost vegetables can raise urine pH (23). This alkalinizing effect of the diet leads to lessof the ionized form of basic drugs (such as gentamicin, quinine, or procainamide) presentedin the renal tubule, leading to more of the drug being reabsorbed. Similarly, theelimination half-life of ephedrine and fexofenadine (Allegra) is increased in the presenceof an alkaline urine pH, possibly leading to increased level of the drug unless the dosingschedule is adjusted (24).Interactions between drugs and foods or alcohol can result in systemic reactions,some of which can be life threatening. Tyramine, an amine that appears in some plantand animal products that have been fermented or aged, is a potent pressor that can causemarked elevation in blood pressure and, in severe cases, hypertensive crisis. Monoamineoxides, found in the liver, GI tract, and adrenergic nerve endings, metabolize tyraminebefore it can reach systemic circulation (25). Monoamine oxidase inhibitators (MAOIs)include drugs used to treat severe depression such as isocarboxazid (Marplan),phenelzine sulfate (Nardil) and tranylcypromine sulfate (Parnate), seligiline (Atapryl,Eldepryl, and Selpak) used to treat Parkinson’s disease, and the antineoplastic drugprocarbazine hydrochloride. If a patient taking these drugs eats foods containingtyramine, it is not metabolized and can cause a rapid increase in blood pressure andincreased incidence of cerebrovascular accidents (CVAs). Examples of foods and beveragesthat contain tyramine include beer, ale, red wines including Chianti, vermouth,homemade breads, cheese, crackers (with cheese), sour cream, bananas, red plums, figs,raisins, avocados, fava beans, Italian broad beans, green bean pods, eggplant, pickledherring, chicken and beef liver, dry sausages, canned meats, salami, yogurt, soup cubes,commercial gravies, chocolate, and soy sauce (26). All of these foods should be avoidedby individuals taking MAOIs.