薬物相互作用

Several drugs are using to obtain a desired therapeutic objective or to treat coexisting diseases. The choice of drugs should be dependent on pharmacological characteristics.
Interactions may be either pharmacokinetic or pharmacodynamic. In pharmacokinetic interaction, drugs may interact at any point during their absorption, distribution, metabolism, or excretion; the result may be an increase or decrease in the concentration of drug at the site of action. Metabolic enzyme, cytochrome P450, which metabolites any drugs is important in pharmacokinetic interaction. As characteristics change in their rates of disposition of using drug, the magnitude of an interaction that changes pharmacokinetic parameter is not always predictable but can be very significant. In pharmacodynamic interaction, drugs may interact at common receptor site or have additive or inhibitory effects due to actions at different sites in an organ.
A drug interaction should be suspected danger when unexpected effects are observed. Careful drug histories are important, because patients may take over-the-counter drugs, may take drugs prescribed by another physician, or may take drugs prescribed for another patient. Care should be exercised when major changes are made in a drug regimen. Then, drugs that are not necessary should be discontinued. The major work of the medical staff of a hospital is to determine if an interaction has occurred and the magnitude of its effect. The interacting drugs should be used effectively with adjustment of dosage or other therapeutic modifications when an interaction is observed.