Loewe additivity

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In pharmacodynamics, Loewe Additivity (or dose additivity) is one of several common reference models used for measuring the effects of drug combinations.

Let and be doses of compounds 1 and 2 producing in combination an effect . We denote by and the doses of compounds 1 and 2 required to produce effect alone (assuming this conditions uniquely define them, i.e. that the individual dose-response functions are bijective). quantifies the potency of compound 1 relatively to that of compound 2.

can be interpreted as the dose of compound 2 converted into the corresponding dose of compound 1 after accounting for difference in potency.

Loewe additivity is defined as the situation where or .

Geometrically, Loewe additivity is the situation where isoboles are segments joining the points and in the domain .

If we denote by , and the dose-response functions of compound 1, compound 2 and of the mixture respectively, then dose additivity holds when


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