Prospective drug information and MNT include basic information about the drug: the name, purpose and duration of prescription of the drug, plus when and how to take the drug. This includes whether to take the drug with or without food. Specific foods and beverages to avoid while taking the drug and potential interactions between drug and vitamin/mineral supplements need to be emphasized. For instance, the patient taking tetracycline (Achromycin-V or Sumycin) or ciprofloxacin (Cipro) should be warned not to combine the drug with milk, yogurt or supplements containing divalent cations, calcium, iron, magnesium, zinc or vitamin-minerals containing any of these cations. 

Potential significant side effects must be delineated. Possible dietary suggestions to relieve side effects should be described.  For instance, information on a high fiber diet with adequate fluids should be part of MNT about an anticholinergic drug, such as oxybutynin (Ditropan) that often causes constipation. Patients should be warned about potential nutritional problems, particularly when dietary intake is inadequate, such as hypokalemia with a potassium depleting diuretic. Dietary changes that may alter drug action should be included, such as the effect of an increase in high vitamin K foods on warfarin (Coumadin) action. Special diet information, such as a low cholesterol, low fat, limited sugar diet with atorvastatin (Lipitor), or other antihyperlipidemic drugs, is essential information. Written information should list medication ingredients such as non-nutrient excipients in the medication (Tables 9 & 10). Examples include lactose, starch, tartrazine, aspartame or alcohol. Individuals with lactose intolerance, celiac disease, allergies, PKU or alcoholism need to avoid or limit one or more of these ingredients.

Retrospective MNT addresses the possibility of food-drug interactions. In order to determine if a patient’s symptom(s) are the result of a food-drug interaction, a complete medical and nutritional history is essential, including prescription and nonprescription drugs, vitamin-mineral supplements and herbal/natural products.  The date of beginning to take the drug(s) versus the date of symptom onset is significant information. It is important to determine the use of nutritional supplements such as enteral products or significant dietary changes, such as fad diets, during the course of drug prescription. Non-nutrients in drugs versus diagnosis of conditions that create intolerance to such ingredients must also be evaluated.

Finally, it is important to investigate the reported incidence of side effects (by percentage as compared with a placebo). For example, for omeprazole (Prilosec) vomiting occurs in 1.5% of those taking the drug versus 4.7% of those taking a placebo. Therefore, in a patient treated with omeprazole it would be appropriate to consider other causes for vomiting. A very rare drug effect is less likely to be the reason for a negative symptom than an effect that is common. 
 

21. Horn T, Pieribone D. Managing Drug Side Effects; 2001. 

22. Pandit MK, et al. Drug-Induced Disorders Of Glucose Tolerance. Ann Int Med 1993;118:529-539.

23. Pronsky ZM. Food-Medication Interactions, 12th edition. Birchrunville, PA: Food Medication Interactions; 2002.