Drug interaction is a situation in which two or more separate drugs have been absorbed into the body and their effects are affected by each other, i.e. the effects are increased or decreased, or they produce a new effect that neither produces on its own.

Differing types of interactions include:

Enzyme inducing - drug A enduces the body to produce more of an enzyme which metabolises drug B thus reducing the effective concentration of the drug B leading to loss of effectiveness of drug B. Drug A effectiveness is not altered

Enzyme reducing - drug A inhibits the production of the enzyme metabolising drug B, thus an elevation of drug B occurs possibly leading to an overdose.

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