The Definition of Relative Potency

The term "relative potency" is utilized primarily in the fields of pharmacology and toxicology. It is essentially synonymous with "potency." In fact, in many glossaries, the term "relative potency" is not even used.

Potency

• The National Institutes of Health defines "potency" as the comparison of the chemical activity of a test compound to that of a standard (reference) compound about which much is already known.

Relative Potency

• According to the St. John's University pharmacological glossary, "relative potency" refers to a comparison of the required quantities of two drugs---an already standard (reference) drug and a newer test drug---to produce the same defined effect. The necessary quantity of the reference drug is divided by the necessary quantity of the test drug to arrive at the ratio of potency.

  Once compared via dose-response analysis, if a lesser amount of one compound is needed than the other to produce the same effect, the first is said to have a higher potency.

Significance

• Such analyses are important in helping doctors determine effective and safe approximate dosages of a plethora of medicines. The dosage can be carefully tailored later to the particular system of the individual.