Define about the Food Effects on Drug Metabolism?

The general tendency of the process of metabolism is to transform a drug from a lipid- soluble to a more water-soluble compound so that it can be handled more easily by the kidneys and excreted in the urine. Food can both inhibit and enhance the metabolism of drugs by altering the activity of the enzyme systems operating in the body. To illustrate, scientists discovered that grapefruit contains natural substances that can affect the way certain prescription medications are broken down (metabolized) by an enzyme, known as CYP3A4 (cytoehrome P-450 3A4). This means that if a person drinks grapefruit juice and takes drugs (such as felodipine, zocor) orally, more of the drug may enter the bloodstream than would have under normal circumstances resulting in a greater pharmacologic effect and possible toxicity. Factors, which affect the deactivation or conjugation of a drug, can thus alter its pharmacological or toxic effects. Periods of short-term starvation or prolonged periods of nutritional inadequacy can influence the effectiveness or safety of drugs.

The amount of a drug required to produce a certain pharmacological effect is determined by the body weight. Sudden reduction in weight or dehydration may therefore result in over dosage. Under-nutrition also reduces the activity of microsomal drug metabolizing enzymes and this can diminish a drug's effectiveness (by reducing its rate of excretion). These are additional reasons for ensuring nutritional adequacy during illness, particularly since this is when pharmacological drug use is most likely to be needed. Alcohol, which is also a drug in its own right often affects microsomal enzyme activity and can potentiate the action of some hypoglycemic drugs or central nervous system (CNS) depressants. The action of certain drugs such as propanolol may be reduced by alcohol. Certain nutrients can also have a direct influence on drug metabolism. Vitamin K reduces the anticoagulant effect of warfarin and the dosage has to be sufficient to counteract the effects of habitual vitamin K intake. Any significant alteration may necessitate adjustment in warfarin dosage. Sodium intake inversely affects serum levels of the mood stabilizer lithium carbonate and since this drug has a narrow range of therapeutic effectiveness, dietary sodium intake must be kept to a constant level in patients receiving this treatment.