In the field of pharmacology, a selective receptor modulator or SRM is a type of drug that has different effects in different tissues.[1] A SRM may behave as an agonist in some tissues while as an antagonist in others. Hence selective receptor modulators are sometimes referred to as tissue selective drugs or mixed agonists / antagonists. This tissue selective behavior is in contrast to many other drugs that behave either as agonists or antagonists regardless of the tissue in question.
Classes of selective receptor modulators include: