NMDR

NMDR is an acronym that most often stands for non-monotonic dose–response, a concept in pharmacology, toxicology, and endocrinology describing dose–response relationships that do not rise or fall consistently with increasing dose. In an NMDR, the magnitude or direction of the effect can be greatest at low or intermediate doses and diminish at higher doses, producing U-shaped or inverted U-shaped curves.

Various biological mechanisms can generate NMDRs. These include the engagement of multiple receptors with different affinities, receptor desensitization or up-regulation, feedback regulation, saturation of metabolic or signaling pathways, and non-receptor mediated effects. Endocrine-disrupting chemicals are a common context for NMDR discussions because they can interact with hormonal systems in complex, dose-dependent ways.

NMDRs have important implications for risk assessment and regulatory science. They challenge the assumption of monotonic dose-response curves that underpin many toxicity tests and extrapolation approaches. Critics note interpretation and statistical challenges, while proponents argue that acknowledging NMDRs improves understanding of low-dose effects and real-world exposures. Regulatory agencies have considered NMDR evidence in weight-of-evidence assessments and testing strategies, though consensus on standard practice remains incomplete.

While NMDR most often refers to non-monotonic dose–response, the acronym may have other domain-specific meanings in different fields. In scientific literature, awareness of NMDR is often tied to discussions of endocrine disruption, pharmacodynamics, and dose–response modeling.