Drug interactions with food

McCabe BJ. Prevention of food-drug interactions with special emphasis on older adults. Curr Opin Clin Null Metab Care. 2004 7 21-26. 

The above illustration should be a clear caution that components of food may interact with drugs, resulting in substantial positive or negative therapeutic effects. As will be noted later, this principle also applies to so-called dietary supplements, including bo-tanicals, used for the treatment of numerous medical conditions. 

Food can interact with drugs, but drugs can also interact with food. Examples of the latter are decreased absorption and elimination of vitamins and minerals, decreased motility, and also taste-, appetite- and vomiting problems (Box 8.4). 

By now you will be comfortable with the idea that the body treats drugs as just another set of chemicals to cope with, and also the idea that drugs interact with many molecules in many sites - with gastric acid, with chemicals in food, with enzymes in the gut and others in the gut wall and liver, with plasma proteins in the blood, and (often transiently) with their tissue receptor once they have got that far. 

This chapter reviews the main mechanisms of drug interactions. It gives some clinically important examples of these, and suggests how they can be assessed and managed. It focuses on drug interactions that may have an adverse clinical outcome, rather than those that are used to therapeutic advantage. The issues of pharmaceutical incompatibility and drug interactions with food and alcohol will not be covered here. 

Flavonoids, as food components or potential drugs, interact with a wide range of proteins by distinct mechanisms weak and rather unspecific binding of tannins to proline-rich or histi-dine-rich random coils leading to protein precipitation, specific enzyme inhibition, and... 

Consistent with their ability to comprehend and cooperate, children should also be given some responsibility for their own health care and for taking medications. This should be discussed in appropriate terms both with the child and with the parents. Possible adverse effects and drug interactions with over-the-counter medicines or foods should also be discussed. Whenever a drug does not achieve its therapeutic effect, the possibility of noncompliance should be considered. There is ample evidence that in such cases parents or children s reports may be grossly inaccurate. Random pill counts and measurement of serum concentrations may help disclose noncompliance. The use of computerized pill containers, which record each lid opening, has been shown to be very effective in measuring compliance. 

Food-medication interaction Determine if food interacts with medication. A food-drug interaction may result in an adverse effect. At times, medication is taken with food to reduce an upsetting side effect of the medication. On the other hand, food can slow absorption for some medications. 

Several other factors that are not included in the MAI also should be assessed (1) suboptimal medication choice (based on effectiveness, safety, cost, and effects on HRQOL), (2) allergy (especially for new prescriptions), (3) undertreatment, and (4) drug interactions with food or laboratory tests. Some additional factors to consider during drug regimen review include adherence, medication storage problems, laboratory monitoring, therapeutic end points, and ADRs. 

Drug interactions with acetaminophen can occur for example, iso-niazid can increase the risk of hepatotoxicity. Chronic ingestion of maximal doses of acetaminophen may intensify the anticoagulant effect in patients taking warfarin, so that such individuals may require closer monitoring. Food decreases the maximum serum concentration of acetaminophen by approximately one-half. 

Avoidance of GI drug absorption difficulties associated with pH, enzymatic activity, drug interactions with food drink, or other orally administered drugs... 

There are advantages and disadvantages to each of these PDE5 inhibitors. Some can be taken with food and other cannot. Some have optimal durations of action, and others are much shorter. All, however, have been known to have adverse effects and drug interactions in common. Some of these adverse effects can be rather severe, and the drug interactions with nitrates can be fatal. 

None of these interactions is very well documented, and their clinical relevance is unclear. Note that vitamin K in food commonly interacts with warfarin, and these interactions are discussed in Coumarins and related drugs + Foods Vitamin Kj-rich , p.409. See also cranberry juice , (p.398), enteral and parenteral nutrition , (below), grapefruit juice , (p.411), mango , (p.408) and soya bean products , (p.408). 

Food-drug interactions Parenteral nutrition In a literature review of all the evidence for and against interactions of antiepileptic drugs with parenteral nutrition, there was no [107 ] clear evidence supporting interactions, but several case reports and anecdotes have shown that alterations in the unbound fraction of antiepileptic drugs may result from combined administration with parenteral nutrition. This may be particularly important when there is hypoalbuminemia (for example, in patients with burns). 

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