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class="vector-toc-numb">2.2</span> <span>Efficacy</span> </div> </a> <ul id="toc-Efficacy-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Relation_to_the_Hill_Equation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Relation_to_the_Hill_Equation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Relation to the Hill Equation</span> </div> </a> <ul id="toc-Relation_to_the_Hill_Equation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Limitations" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Limitations"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Limitations</span> </div> </a> <ul id="toc-Limitations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a 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src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d2/Dose_response_antagonist.jpg/400px-Dose_response_antagonist.jpg" decoding="async" width="400" height="190" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/d/d2/Dose_response_antagonist.jpg 1.5x" data-file-width="587" data-file-height="279" /></a><figcaption>The tissue response (y-axis) to an agonist, in log concentration (x-axis), in the presence of different antagonist concentrations. The EC<sub>50</sub> of the agonist is represented by the x co-ordinate that corresponds with the half-maximum of the leftmost curve. This is denoted by [A]</figcaption></figure> <p><b>Half maximal effective concentration</b> (<b>EC<sub>50</sub></b>) is a measure of the concentration of a drug, antibody or toxicant which induces a <a href="/wiki/Stimulus%E2%80%93response_model" title="Stimulus–response model">biological response</a> halfway between the baseline and maximum after a specified exposure time.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> More simply, EC<sub>50</sub> can be defined as the <i>concentration required to obtain a 50% [...] effect</i><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> and may be also written as [A]<sub>50</sub>.<sup id="cite_ref-Terms_3-0" class="reference"><a href="#cite_note-Terms-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> It is commonly used as a measure of a drug's <a href="/wiki/Potency_(pharmacology)" title="Potency (pharmacology)">potency</a>, although the use of EC<sub>50</sub> is preferred over that of 'potency', which has been criticised for its vagueness.<sup id="cite_ref-Terms_3-1" class="reference"><a href="#cite_note-Terms-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> EC<sub>50</sub> is a measure of concentration, expressed in <a href="/wiki/Molar_concentration" title="Molar concentration">molar units</a> (M), where 1 M is equivalent to 1 <a href="/wiki/Mole_(unit)" title="Mole (unit)">mol</a>/<a href="/wiki/Liter" class="mw-redirect" title="Liter">L</a>. </p><p>The EC<sub>50</sub> of a <i>graded</i> <a href="/wiki/Dose_response_curve" class="mw-redirect" title="Dose response curve">dose response curve</a> therefore represents the concentration of a compound where 50% of its maximal effect is observed.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The EC<sub>50</sub> of a <i>quantal</i> dose response curve represents the concentration of a compound where 50% of the population exhibit a response,<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> after a specified exposure duration. </p><p>For clarification, a graded dose response curve shows the graded effect of the drug (y axis) over the dose of the drug (x axis) in one or an average of subjects. A quantal dose response curve shows the percentage of subjects where a response is noted in an all-or-none manner (y axis) over the dose of the drug (x axis). </p><p>For competition binding assays and functional antagonist assays <a href="/wiki/IC50" title="IC50">IC<sub>50</sub></a> is the most common summary measure of the dose-response curve. For agonist/stimulator assays the most common summary measure is the EC<sub>50</sub>.<sup id="cite_ref-Assay_6-0" class="reference"><a href="#cite_note-Assay-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>The EC<sub>50</sub> is also related to <a href="/wiki/IC50" title="IC50">IC<sub>50</sub></a> which is a measure of a compound's inhibition (50% inhibition). </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Calculation_of_EC50">Calculation of EC<sub>50</sub></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=1" title="Edit section: Calculation of EC50"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Biological responses to <a href="/wiki/Ligand_(biochemistry)" title="Ligand (biochemistry)">ligand</a> concentrations typically follow a <a href="/wiki/Sigmoid_function" title="Sigmoid function">sigmoidal</a> function. The <a href="/wiki/Inflection_point" title="Inflection point">inflection point</a> at which the increase in response with increasing ligand concentration begins to slow is the EC<sub>50</sub>, which can be mathematically determined by derivation of the best-fit line. While relying on a graph for estimation is more convenient, this typical method yields less accurate and precise results.<sup id="cite_ref-Assay_6-1" class="reference"><a href="#cite_note-Assay-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>The response or effect, E, is dependent on both the binding of the drug and the drug-bound receptor. The <a href="/wiki/Agonist" title="Agonist">agonist</a> that binds to the receptor and initiates the response is usually abbreviated A or D. At low agonist concentrations, [A], the response, E is immeasurably low but at higher [A], E becomes measurable. E increases with [A] until at sufficiently high [A], when E plateaus towards an asymptotic maximum attainable response, E<sub>max</sub>. The [A] at which E is 50% of E<sub>max</sub> is termed the <a href="/wiki/Half_maximal_effective_concentration" class="mw-redirect" title="Half maximal effective concentration">half maximal effective concentration</a> and is abbreviated EC<sub>50</sub>, or rarely [A]<sub>50</sub>. The term "potency" refers to the EC<sub>50</sub> value. The lower the EC<sub>50</sub>, the less the concentration of a drug is required to produce 50% of maximum effect and the higher the potency. The EC<sub>10</sub> and EC<sub>90</sub> concentrations to induce 10% and 90% maximal responses are defined similarly. </p><p> There is a wide range of EC<sub>50</sub> values of drugs; they are typically anywhere from nM to mM. Hence, it is often more practical to refer to the logarithmically transformed <b>p</b>EC<sub>50</sub> values instead of EC<sub>50</sub>, where</p><blockquote><p><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {pEC50}}=-\log _{10}({\ce {EC50}})}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>pEC</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>50</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> <mo>=</mo> <mo>−</mo> <msub> <mi>log</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>10</mn> </mrow> </msub> <mo>⁡</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>EC</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>50</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {pEC50}}=-\log _{10}({\ce {EC50}})}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3d205a772f96cfcbd6a0746e0a3b8cea4b92f6ab" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:23.518ex; height:3.009ex;" alt="{\displaystyle {\ce {pEC50}}=-\log _{10}({\ce {EC50}})}" /></span>.</p></blockquote> <div class="mw-heading mw-heading2"><h2 id="Relation_to_affinity_and_efficacy">Relation to affinity and efficacy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=2" title="Edit section: Relation to affinity and efficacy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A drug's potency is dependent on the drug's <a href="/wiki/Dissociation_constant#Protein-ligand_binding" title="Dissociation constant">affinity</a> and <a href="/wiki/Intrinsic_activity" title="Intrinsic activity">efficacy</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Affinity">Affinity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=3" title="Edit section: Affinity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Dissociation_constant#Protein-ligand_binding" title="Dissociation constant">Affinity</a> describes how well a drug can bind to a receptor. Faster or stronger binding is represented by a higher affinity, or equivalently a lower dissociation constant. The EC<sub>50</sub> should not be confused with the affinity constant, K<sub>d</sub>. While the former reflects the drug concentration needed for a level of tissue response, the latter reflects the drug concentration needed for an amount of receptor binding. </p> <div class="mw-heading mw-heading3"><h3 id="Efficacy">Efficacy</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=4" title="Edit section: Efficacy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Intrinsic_activity" title="Intrinsic activity">Efficacy</a> is the relationship between receptor occupancy and the ability to initiate a response at the molecular, cellular, tissue or system level. </p> <div class="mw-heading mw-heading2"><h2 id="Relation_to_the_Hill_Equation">Relation to the Hill Equation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=5" title="Edit section: Relation to the Hill Equation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The EC<sub>50</sub> relates to the <a href="/wiki/Hill_equation_(biochemistry)" title="Hill equation (biochemistry)">Hill equation</a>, which is a function of the agonist concentration, [A]: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle E={\frac {{[A]}^{n}\times {E_{\mathrm {max} }}}{{[A]}^{n}+\mathrm {EC} _{50}^{n}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>E</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">[</mo> <mi>A</mi> <mo stretchy="false">]</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>n</mi> </mrow> </msup> <mo>×</mo> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">x</mi> </mrow> </mrow> </msub> </mrow> </mrow> <mrow> <msup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">[</mo> <mi>A</mi> <mo stretchy="false">]</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>n</mi> </mrow> </msup> <mo>+</mo> <msubsup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">E</mi> <mi mathvariant="normal">C</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>50</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>n</mi> </mrow> </msubsup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle E={\frac {{[A]}^{n}\times {E_{\mathrm {max} }}}{{[A]}^{n}+\mathrm {EC} _{50}^{n}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/655b52301235f8884480e0b617f5b5e6d2759623" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:17.943ex; height:6.509ex;" alt="{\displaystyle E={\frac {{[A]}^{n}\times {E_{\mathrm {max} }}}{{[A]}^{n}+\mathrm {EC} _{50}^{n}}}}" /></span><sup id="cite_ref-Terms_3-2" class="reference"><a href="#cite_note-Terms-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></dd></dl> <p>where E is the observed response or effect above baseline, and n, the <a href="/wiki/Hill_equation_(biochemistry)#Interpretation_of_Hill_Coefficient" title="Hill equation (biochemistry)">Hill coefficient</a> reflects the slope of the curve.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>The EC<sub>50</sub> represents the <a href="/wiki/Point_of_inflection" class="mw-redirect" title="Point of inflection">point of inflection</a> of the Hill equation, beyond which increases of [A] have less impact on E. In <a href="/wiki/Dose_response_curves" class="mw-redirect" title="Dose response curves">dose response curves</a>, the logarithm of [A] is often taken, turning the Hill equation into a sigmoidal <a href="/wiki/Logistic_function" title="Logistic function">logistic function</a>. In this case, the EC<sub>50</sub> represents the rising section of the sigmoid curve. </p> <div class="mw-heading mw-heading2"><h2 id="Limitations">Limitations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=6" title="Edit section: Limitations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The effects of a stressor or drug generally depend on the exposure time. Therefore, the EC<sub>50</sub> (and similar statistics) will be a function of exposure time. The exact shape of this time function will depend upon the stressor (e.g., the specific toxicant), its mechanism of action, the organism exposed, etc. This time dependency hampers the comparison of <a href="/wiki/Potency_(pharmacology)" title="Potency (pharmacology)">potency</a> or <a href="/wiki/Toxicity" title="Toxicity">toxicity</a> between compounds and between different organisms. </p><p>A drug will not have a single value of EC<sub>50</sub> due to different tissues having different sensitivities to the drug (in part due to tissue specific receptor expression).<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (April 2019)">citation needed</span></a></i>]</sup> Furthermore, EC<sub>50</sub> is dependent on many factors including species, tissue and cell type and genetics.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (April 2019)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=7" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Measures_of_pollutant_concentration" title="Measures of pollutant concentration">Measures of pollutant concentration</a></li> <li><a href="/wiki/Certain_safety_factor" class="mw-redirect" title="Certain safety factor">Certain safety factor</a></li> <li><a href="/wiki/LD50" class="mw-redirect" title="LD50">LD<sub>50</sub></a> (median lethal dose)</li> <li><a href="/wiki/Therapeutic_index" title="Therapeutic index">Therapeutic index</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=8" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120730150339/http://www.graphpad.com/curvefit/introduction89.htm">"Introducing dose response curves"</a>. Graphpad Software. Archived from <a rel="nofollow" class="external text" href="http://www.graphpad.com/curvefit/introduction89.htm">the original</a> on 2012-07-30.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Introducing+dose+response+curves&rft.pub=Graphpad+Software&rft_id=http%3A%2F%2Fwww.graphpad.com%2Fcurvefit%2Fintroduction89.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEC50" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFChenBertinFroldi2013" class="citation journal cs1">Chen, Zheng; Bertin, Riccardo; Froldi, Guglielmina (2013-05-01). <a rel="nofollow" class="external text" href="https://www.sciencedirect.com/science/article/pii/S0308814612016020">"EC50 estimation of antioxidant activity in DPPH assay using several statistical programs"</a>. <i>Food Chemistry</i>. <b>138</b> (1): <span class="nowrap">414–</span>420. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.foodchem.2012.11.001">10.1016/j.foodchem.2012.11.001</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0308-8146">0308-8146</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/23265506">23265506</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Food+Chemistry&rft.atitle=EC50+estimation+of+antioxidant+activity+in+DPPH+assay+using+several+statistical+programs&rft.volume=138&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E414-%3C%2Fspan%3E420&rft.date=2013-05-01&rft.issn=0308-8146&rft_id=info%3Apmid%2F23265506&rft_id=info%3Adoi%2F10.1016%2Fj.foodchem.2012.11.001&rft.aulast=Chen&rft.aufirst=Zheng&rft.au=Bertin%2C+Riccardo&rft.au=Froldi%2C+Guglielmina&rft_id=https%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0308814612016020&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEC50" class="Z3988"></span></span> </li> <li id="cite_note-Terms-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Terms_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Terms_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Terms_3-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFNeubig2003" class="citation journal cs1">Neubig, Richard R. (2003). <a rel="nofollow" class="external text" href="https://www.guidetopharmacology.org/pdfs/termsAndSymbols.pdf">"International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. XXXVIII. Update on Terms and Symbols in Quantitative Pharmacology"</a> <span class="cs1-format">(PDF)</span>. <i>Pharmacological Reviews</i>. <b>55</b> (4): <span class="nowrap">597–</span>606. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1124%2Fpr.55.4.4">10.1124/pr.55.4.4</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/14657418">14657418</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:1729572">1729572</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Pharmacological+Reviews&rft.atitle=International+Union+of+Pharmacology+Committee+on+Receptor+Nomenclature+and+Drug+Classification.+XXXVIII.+Update+on+Terms+and+Symbols+in+Quantitative+Pharmacology&rft.volume=55&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E597-%3C%2Fspan%3E606&rft.date=2003&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1729572%23id-name%3DS2CID&rft_id=info%3Apmid%2F14657418&rft_id=info%3Adoi%2F10.1124%2Fpr.55.4.4&rft.aulast=Neubig&rft.aufirst=Richard+R.&rft_id=https%3A%2F%2Fwww.guidetopharmacology.org%2Fpdfs%2FtermsAndSymbols.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEC50" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20100614210858/http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-E/EC50.html">"Northwestern Molbiosci EC50 definition"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-E/EC50.html">the original</a> on 2010-06-14<span class="reference-accessdate">. Retrieved <span class="nowrap">2019-05-27</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Northwestern+Molbiosci+EC50+definition&rft_id=http%3A%2F%2Fwww.biochem.northwestern.edu%2Fholmgren%2FGlossary%2FDefinitions%2FDef-E%2FEC50.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEC50" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070220004824/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F190116.htm">"Drug Dose and Clinical Response"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F190116.htm">the original</a> on 2007-02-20<span class="reference-accessdate">. Retrieved <span class="nowrap">2019-04-16</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Drug+Dose+and+Clinical+Response&rft_id=http%3A%2F%2Fwww.merckvetmanual.com%2Fmvm%2Findex.jsp%3Fcfile%3Dhtm%252Fbc%252F190116.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEC50" class="Z3988"></span></span> </li> <li id="cite_note-Assay-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-Assay_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Assay_6-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.ncgc.nih.gov/guidance/section3.html">Assay Operations for SAR Support</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20061129102848/http://www.ncgc.nih.gov/guidance/section3.html">Archived</a> 2006-11-29 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> NIH Chemical Genomics Center</span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.sigmaplot.com/products/sigmaplot/Standard_Curves_Analysis.pdf">EC50 equation</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120417121807/http://www.sigmaplot.com/products/sigmaplot/Standard_Curves_Analysis.pdf">Archived</a> 2012-04-17 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=EC50&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060517233647/http://www.unmc.edu/Pharmacology/receptortutorial/competition/IC50.htm">Determination of IC<sub>50</sub> values</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": 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4em"><a href="/wiki/Pharmacology" title="Pharmacology">Pharmacology</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Ligand_(biochemistry)" title="Ligand (biochemistry)">Ligand (biochemistry)</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Excitatory10" scope="row" class="navbox-group" style="width:1%;text-align: center;">Excitatory</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Agonist" title="Agonist">Agonist</a></li> <li><a href="/wiki/Endogenous_agonist" title="Endogenous agonist">Endogenous agonist</a></li> <li><a href="/wiki/Irreversible_agonist" title="Irreversible agonist">Irreversible agonist</a></li> <li><a href="/wiki/Partial_agonist" title="Partial agonist">Partial agonist</a></li> <li><a href="/wiki/Superagonist" title="Superagonist">Superagonist</a></li> <li><a href="/wiki/Physiological_agonism_and_antagonism" title="Physiological agonism and antagonism">Physiological agonist</a></li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Inhibitory10" scope="row" class="navbox-group" style="width:1%;text-align: center;">Inhibitory</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Receptor_antagonist" title="Receptor antagonist">Antagonist</a></li> <li><a href="/wiki/Competitive_antagonist" class="mw-redirect" title="Competitive antagonist">Competitive antagonist</a></li> <li><a href="/wiki/Irreversible_antagonist" title="Irreversible antagonist">Irreversible antagonist</a></li> <li><a href="/wiki/Physiological_agonism_and_antagonism" title="Physiological agonism and antagonism">Physiological antagonist</a></li> <li><a href="/wiki/Inverse_agonist" title="Inverse agonist">Inverse agonist</a></li> <li><a href="/wiki/Enzyme_inhibitor" title="Enzyme inhibitor">Enzyme inhibitor</a></li></ul> </div></td></tr></tbody></table><div> <ul><li><a href="/wiki/Drug" title="Drug">Drug</a></li> <li><a href="/wiki/Neurotransmitter" title="Neurotransmitter">Neurotransmitter</a></li> <li><a href="/wiki/Agonist-antagonist" title="Agonist-antagonist">Agonist-antagonist</a></li> <li><a href="/wiki/Pharmacophore" title="Pharmacophore">Pharmacophore</a></li></ul></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Pharmacodynamics" title="Pharmacodynamics">Pharmacodynamics</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Activity_at_receptor20" scope="row" class="navbox-group" style="width:1%;text-align: center;">Activity at receptor</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <li><a href="/wiki/Mechanism_of_action" title="Mechanism of action">Mechanism of action</a></li> <li><a href="/wiki/Mode_of_action" title="Mode of action">Mode of action</a></li> <li><a href="/wiki/Molecular_binding" title="Molecular binding">Binding</a></li> <li><a href="/wiki/Receptor_(biochemistry)" title="Receptor (biochemistry)">Receptor (biochemistry)</a></li> <li><a href="/wiki/Desensitization_(medicine)" title="Desensitization (medicine)">Desensitization (medicine)</a></li> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Other_effects_of_ligand23" scope="row" class="navbox-group" style="width:1%;text-align: center;">Other effects of ligand</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Selectivity (<a href="/wiki/Binding_selectivity" title="Binding selectivity">Binding</a>, <a href="/wiki/Functional_selectivity" title="Functional selectivity">Functional</a>)</li> <li><a href="/wiki/Pleiotropy_(drugs)" title="Pleiotropy (drugs)">Pleiotropy (drugs)</a></li> <li><a href="/wiki/Non-specific_effect_of_vaccines" title="Non-specific effect of vaccines">Non-specific effect of vaccines</a></li> <li><a href="/wiki/Adverse_effect" title="Adverse effect">Adverse effect</a></li> <li><a href="/wiki/Toxicity" title="Toxicity">Toxicity</a> (<a href="/wiki/Neurotoxicity" title="Neurotoxicity">Neurotoxicity</a>)</li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Analysis8" scope="row" class="navbox-group" style="width:1%;text-align: center;">Analysis</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Dose%E2%80%93response_relationship" title="Dose–response relationship">Dose–response relationship</a></li> <li><a href="/wiki/Hill_equation_(biochemistry)" title="Hill equation (biochemistry)">Hill equation (biochemistry)</a></li> <li><a href="/wiki/Schild_plot" class="mw-redirect" title="Schild plot">Schild plot</a></li> <li><a href="/wiki/Del_Castillo_Katz_model" class="mw-redirect" title="Del Castillo Katz model">Del Castillo Katz model</a></li> <li><a href="/wiki/Cheng-Prussoff_Equation" class="mw-redirect" title="Cheng-Prussoff Equation">Cheng-Prussoff Equation</a></li> <li>Methods (<a href="/wiki/Organ_bath" title="Organ bath">Organ bath</a>, <a href="/wiki/Ligand_binding_assay" title="Ligand binding assay">Ligand binding assay</a>, <a href="/wiki/Patch_clamp" title="Patch clamp">Patch clamp</a>)</li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Metrics7" scope="row" class="navbox-group" style="width:1%;text-align: center;">Metrics</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Efficacy#Pharmacology" title="Efficacy">Efficacy</a></li> <li><a href="/wiki/Intrinsic_activity" title="Intrinsic activity">Intrinsic activity</a></li> <li><a href="/wiki/Potency_(pharmacology)" title="Potency (pharmacology)">Potency</a> (<a class="mw-selflink selflink">EC50</a>, <a href="/wiki/IC50" title="IC50">IC50</a>, <a href="/wiki/Effective_dose_(pharmacology)" title="Effective dose (pharmacology)">ED50</a>, <a href="/wiki/Median_lethal_dose" title="Median lethal dose">LD50</a>, <a href="/wiki/Median_toxic_dose" title="Median toxic dose">TD50</a>)</li> <li><a href="/wiki/Therapeutic_index" title="Therapeutic index">Therapeutic index</a></li> <li><a href="/wiki/Dissociation_constant#Protein-ligand_binding" title="Dissociation constant">Affinity</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Pharmacokinetics" title="Pharmacokinetics">Pharmacokinetics</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Metrics7" scope="row" class="navbox-group" style="width:1%;text-align: center;">Metrics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Loading_dose" title="Loading dose">Loading dose</a></li> <li><a href="/wiki/Volume_of_distribution" title="Volume of distribution">Volume of distribution</a> (<a href="/wiki/Initial_volume_of_distribution" title="Initial volume of distribution">Initial</a>)</li> <li><a href="/wiki/Rate_of_infusion" title="Rate of infusion">Rate of infusion</a></li> <li><a href="/wiki/Onset_of_action" title="Onset of action">Onset of action</a></li> <li><a href="/wiki/Biological_half-life" title="Biological half-life">Biological half-life</a></li> <li><a href="/wiki/Plasma_protein_binding" title="Plasma protein binding">Plasma protein binding</a></li> <li><a href="/wiki/Bioavailability" title="Bioavailability">Bioavailability</a></li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="LADME5" scope="row" class="navbox-group" style="width:1%;text-align: center;">LADME</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/ADME" title="ADME">(L)ADME</a>: (<a href="/wiki/Liberation_(pharmacology)" title="Liberation (pharmacology)">Liberation</a>)</li> <li><a href="/wiki/Absorption_(pharmacology)" title="Absorption (pharmacology)">Absorption</a></li> <li><a href="/wiki/Distribution_(pharmacology)" title="Distribution (pharmacology)">Distribution</a></li> <li><a href="/wiki/Drug_metabolism" title="Drug metabolism">Metabolism</a></li> <li><a href="/wiki/Excretion" title="Excretion">Excretion</a> (<a href="/wiki/Clearance_(pharmacology)" title="Clearance (pharmacology)">Clearance</a>)</li></ul> </div></td></tr></tbody></table><div> <ul><li><a href="/wiki/Compartment_(pharmacokinetics)" title="Compartment (pharmacokinetics)">Compartment</a></li> <li><a href="/wiki/Bioequivalence" title="Bioequivalence">Bioequivalence</a></li></ul></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Related<br /> fields</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Neuroscience_and_psychology35" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Neuroscience" title="Neuroscience">Neuroscience</a> and <a href="/wiki/Psychology" title="Psychology">psychology</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <li><a href="/wiki/Neuropsychopharmacology" title="Neuropsychopharmacology">Neuropsychopharmacology</a></li> <li><a href="/wiki/Neuropharmacology" title="Neuropharmacology">Neuropharmacology</a></li> <li><a href="/wiki/Psychopharmacology" title="Psychopharmacology">Psychopharmacology</a></li> <li><a href="/wiki/Electrophysiology" title="Electrophysiology">Electrophysiology</a></li> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Medicine12" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Medicine" title="Medicine">Medicine</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Clinical_pharmacology" title="Clinical pharmacology">Clinical pharmacology</a></li> <li><a href="/wiki/Pharmacy" title="Pharmacy">Pharmacy</a></li> <li><a href="/wiki/Medicinal_chemistry" title="Medicinal chemistry">Medicinal chemistry</a></li> <li><a href="/wiki/Pharmacoepidemiology" title="Pharmacoepidemiology">Pharmacoepidemiology</a></li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Biochemistry_and_genetics33" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Biochemistry" title="Biochemistry">Biochemistry</a> and <a href="/wiki/Genetics" title="Genetics">genetics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pharmacoinformatics" title="Pharmacoinformatics">Pharmacoinformatics</a></li> <li><a href="/wiki/Pharmacogenetics" class="mw-redirect" title="Pharmacogenetics">Pharmacogenetics</a></li> <li><a href="/wiki/Pharmacogenomics" title="Pharmacogenomics">Pharmacogenomics</a></li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Toxicology14" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Toxicology" title="Toxicology">Toxicology</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pharmacotoxicology" title="Pharmacotoxicology">Pharmacotoxicology</a></li> <li><a href="/wiki/Neurotoxicology" class="mw-redirect" title="Neurotoxicology">Neurotoxicology</a></li></ul> </div></td></tr></tbody></table><div> </div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Drug_discovery18" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Drug_discovery" title="Drug discovery">Drug discovery</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Classical_pharmacology" title="Classical pharmacology">Classical pharmacology</a></li> <li><a href="/wiki/Reverse_pharmacology" title="Reverse pharmacology">Reverse pharmacology</a></li></ul> </div></td></tr></tbody></table><div> <ul><li><a href="/wiki/Photopharmacology" title="Photopharmacology">Photopharmacology</a></li> <li><a href="/wiki/Immunopharmacology" class="mw-redirect" title="Immunopharmacology">Immunopharmacology</a></li> <li><a href="/wiki/Cell_biology" title="Cell biology">Cell biology</a></li> <li><a href="/wiki/Physiology" title="Physiology">Physiology</a></li></ul></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Other</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <li><a href="/wiki/Coinduction_(anesthetics)" title="Coinduction (anesthetics)">Coinduction (anesthetics)</a></li> <li><a href="/wiki/Combination_therapy" title="Combination therapy">Combination therapy</a></li> <li><a href="/wiki/Functional_analog_(chemistry)" title="Functional analog (chemistry)">Functional analog (chemistry)</a></li> <li><a href="/wiki/Polypharmacology" title="Polypharmacology">Polypharmacology</a></li> <li><a href="/wiki/Chemotherapy" title="Chemotherapy">Chemotherapy</a></li> <li><a href="/wiki/Lists_of_drugs" title="Lists of drugs">Lists of drugs</a></li> <li><a href="/wiki/WHO_list_of_essential_medicines" class="mw-redirect" title="WHO list of 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