Selective receptor modulator

{{Infobox drug class

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| Caption = Tamoxifen, a {{abbrlink|SERM|selective estrogen receptor modulator}} and a widely used drug in the treatment of breast cancer.

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| Synonyms = SRM

| Use = Various

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| Biological_target = Steroid hormone receptor

| Chemical_class = Steroidal; Nonsteroidal

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In the field of pharmacology, a selective receptor modulator or SRM is a type of drug that has different effects in different tissues.{{cite journal | vauthors = Smith CL, O'Malley BW | title = Coregulator function: a key to understanding tissue specificity of selective receptor modulators | journal = Endocr. Rev.| volume = 25 | issue = 1 | pages = 45–71 |date=February 2004 | pmid = 14769827 | doi = 10.1210/er.2003-0023| doi-access = free }} An 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.