Definition/Introduction
The ED50 is the dose of a medication that produces a specific effect in 50% of the population that has been administered that dose. This metric can be used clinically by clinicians for a particular drug effect. However, depending on the risk-benefit analysis, clinicians may use a different dosage for their intended outcome. The toxic dose in 50% of the population is called TD50; the ED50 should be much less than the TD50, as this would indicate an effective medication at a lower dose.[1] The ED50 for a particular medication is derived from a dose-response curve, in which the ED50 is at the dosage (x-axis), where there is 50% of the desired response (y-axis).
The ED50 should be used as a clinical starting point for clinicians when prescribing medications, as dosage adjustments are made to balance efficacy and toxicity. The E-max would be equivalent to the maximum effect the drug may have. It is important to remember that as dosages increase, the risk for toxicities will increase and may not be directly proportionate. Each patient requires individualized treatment goals and should be monitored to ensure the lowest effective dose possible, especially for long-term treatment.
There are two dose-response curve (DRC) forms: graded and quantal. Graded answers the question, ‘How much?’ whereas quantal DRC answers, ‘Yes or no?’ The ED50 may change depending on the question the clinician is trying to answer; using the recommended ED50 as a starting point is recommended, making adjustments based on the clinical outcomes.