The following pharmacological definition has been taken from the Pharmacology and Experimental Therapeutics Department Glossary at Boston University School of Medicine.
The maximum biological effect that can be induced in a tissue by a given drug, regardless of how large a dose is administered. The maximum effect produced by a given drug may be less than the maximum response of which the reacting tissue is capable, and less than the maximum response that can be induced by another drug of greater intrinsic activity. “Ceiling” is analogous to the maximum reaction velocity of an enzymatic reaction when the enzyme is saturated with substrate.
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