Abstract: Pharmacological interaction is identified among other aspects when the effects of a drug are significantly altered clinically by the presence of food. The most important clinical significance in the history of drug-food interactions occurred in the fifties, the vitamin B6 deficiency when administering the tuberculostatic isoniazide, but there is no doubt that the interaction in the sixties between drugs that were inhibitors of the enzyme mono-amine oxidase and the biogenic amines tyramine and histamine had an important clinical significance due to the increase in hypertension and deaths due to cerebro-vascular accidents. In the seventies the types of interactions were due to the chelation between tetracyclines and the calcium of milk products, influencing the bioavailability of the antibiotic, and from this point on, studies explore in depth the interaction of foods with the different steps in the pharmacokinetics of the drugs (absorption, distribution, metabolization, and excretion), and these have helped to explain the metabolization interactions of drugs like the clinical significance between grapefruit juice whose naringenine flavonoid is a powerful inhibitor of cytochrome 450, particularly the CYP3A4 family, and terfenadine (antihistamine), with an increase in the plasma levels of the drug and patient death due to ventricular arrhythmia. In the USA the Joint Commission on Accreditation of Health Care Organization (JCAHO) has recommended monitoring of the possible drug and food interactions since 1985, and recommends that patients be informed of this. Despite the recommendations of the JCAHO, few American hospitals have protocolized these interactions and even fewer comply with these, and according to some authors, this is due to the lack of motivation caused by the lack of clinical significance. In this chapter we will study the effect of foods on drugs in two aspects: at the pharamcokinetic level with the possible alterations in absorption, distribution, metabolization, and excretion, and at the pharamcodynamic level, by alterations in the action of the drug. Also, based on a study by Delgado, which we have changed somewhat, we will report how the drugs should be taken to avoid interactions with foods. As a conclusion, it is difficult to establish which are the relevant drug-food interactions, unless they have given clinical problems. The following are important: a) drugs with a narrow therapeutic margin in which an absorption problem or a metabolization problem may disrupt the plasma levels and the patient needs (digoxin, teophylline, cyclosporin, etc). And b) the drugs like some antibiotics that, because of their action mechanisms, need to maintain adequate plasma concentrations.
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