This quantitative measure indicates how much of a particular drug or other substance -LRB- inhibitor -RRB- is needed to inhibit a given biological process -LRB- or component of a process , i.e. an enzyme , cell , cell receptor or microorganism -RRB- by half .

It indicates how much of a particular drug or other substance is needed to inhibit a given biological process -LRB- or component of a process , i.e. an enzyme , cell , cell receptor or microorganism -RRB- by half .
