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M. T. SAN MIGUEL Y COLS. AN. R. ACAD. NAC. FARM.

These interactions can be prevented by a coordinated action of the health care
team.

Key words: Drug interaction.— Drug – food interaction.— Drug – nutrient
interaction

Extensive summary

Adverse drug reactions and iatrogenic diseases have been identified as relevant
events leading to patients´ morbidity and mortality. In this context, drug - food
interactions can produce negative effects in the safety and efficacy of drug therapy
as well as in the nutritional status of the patient. The proportion of adverse reac-
tions due to drug – food interactions is unknown and, often, only in case that a
serious adverse reaction is observed, this type of event receives the adequate atten-
tion.

Drug – food interactions have been investigated since decades. The first reports
describe potential changes in drug absorption during concomitant food intake, as
it is the case for tetracycline and isoniazide. Subsequently, relevant interactions
were identified, such as the deficiency of vitamin B6 induced by isoniazide and the
interaction between monoamine-oxidase inhibitors and the amine tiramine contai-
ned in fermented food, which leads to hypertensive events. However, it has been
during the last decade when the number of publications about drug – food interac-
tions has raised significantly.

An update of drug - food interactions with potential clinical consequences was
carried out. They can be classified in two types, depending on the substrate (drug
or nutrient) that exerts its effect on the other. However, in some cases, both subs-
trates can be affected.

Occasionally, an interaction can have a beneficial effect, affecting the drug
absorption when it is taken with a meal, which reduces its side effects leading to
a correct drug intake; but the increase in drug concentration observed with other
drugs can produce serious toxicity so that, the term «interaction» is usually asso-
ciated with a potentially clinically negative effect.

The main factors that influence the appearance of a drug – food interaction are
considered:

— The physico – chemical and enantiomorphic composition of the drug.
— The time between the meal and the drug intake.
— The amount and composition of the meal (mainly fat, protein and fiber).
— The dose of the drug.
The magnitude and the incidence of a certain drug – food interaction shows
a high inter and intra- patient variability and, in a real situation, it is difficult
to predict accurately the outcome when a patient receives simultaneously a drug
and a meal. Significant factors seem to be the characteristics of the exposed
subject, including age, nutritional status and associated pathology. In this regard,
particular attention should be given to the elderly population. Regarding the me-
chanism of the interaction, it can be physical-chemical, pharmacokinetic or phar-
macodynamic.

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