Idiosyncratic drug reactions,
also known as type B reactions,
are drug
reactions that occur rarely and unpredictably amongst the
population. Idiosyncratic drug reactions appear to not be concentration
dependent. A minimal amount of drug will cause an immune response, but it is
suspected that at a low enough concentration, a drug will be less likely to
initiate an immune response.
also known as type B reactions,
are drug
reactions that occur rarely and unpredictably amongst the
population. Idiosyncratic drug reactions appear to not be concentration
dependent. A minimal amount of drug will cause an immune response, but it is
suspected that at a low enough concentration, a drug will be less likely to
initiate an immune response.
Mechanism
In
adverse drug reactions involving overdoses, the toxic effect is simply an
extension of the pharmacological effect (Type A adverse drug reactions). On the
other hand, clinical symptoms of idiosyncratic drug reactions (Type B adverse
drug reactions) are different from the pharmacological effect of the drug.
adverse drug reactions involving overdoses, the toxic effect is simply an
extension of the pharmacological effect (Type A adverse drug reactions). On the
other hand, clinical symptoms of idiosyncratic drug reactions (Type B adverse
drug reactions) are different from the pharmacological effect of the drug.
The
proposed mechanism of most idiosyncratic drug reactions is immune-mediated
toxicity. To create an immune response, a foreign molecule must be present that
antibodies can bind to (i.e. the antigen) and cellular damage must exist. Very
often, drugs will not be immunogenic because they are too small to induce
immune response.
proposed mechanism of most idiosyncratic drug reactions is immune-mediated
toxicity. To create an immune response, a foreign molecule must be present that
antibodies can bind to (i.e. the antigen) and cellular damage must exist. Very
often, drugs will not be immunogenic because they are too small to induce
immune response.
However,
a drug can cause an immune response if the drug binds a larger molecule. Some
unaltered drugs, such as penicillin, will bind avidly to proteins. Others must
be bioactivated into a toxic compound that will in turn bind to proteins. The second
criterion of cellular damage can come either from a toxic drug/drug metabolite,
or from an injury or infection. These will sensitize the immune system to the
drug and cause a response. Idiosyncratic reactions fall conventionally under
toxicology.
a drug can cause an immune response if the drug binds a larger molecule. Some
unaltered drugs, such as penicillin, will bind avidly to proteins. Others must
be bioactivated into a toxic compound that will in turn bind to proteins. The second
criterion of cellular damage can come either from a toxic drug/drug metabolite,
or from an injury or infection. These will sensitize the immune system to the
drug and cause a response. Idiosyncratic reactions fall conventionally under
toxicology.