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On-Target Toxicity

Meaning

An adverse effect or toxicity that arises directly from the therapeutic agent binding to its intended biological target, but where the resulting biological activity is either excessive, prolonged, or occurs in a non-desired tissue. In hormonal health, this means that while the drug is hitting the correct receptor, the resulting pharmacological effect is detrimental, such as administering a testosterone dose that correctly stimulates the androgen receptor but leads to an unacceptably high red blood cell count. This type of toxicity is inherent to the drug’s mechanism and is typically dose-dependent.