Potency (pharmacology)

For other uses, see Potency (disambiguation).

Concentration-response curves illustrating the concept of potency. For a response of 0.25a.u., Drug B is more potent, as it generates this response at a lower concentration. For a response of 0.75a.u., Drug A is more potent. a.u. refers to "arbitrary units".

In pharmacology, potency or biological potency ^[1] is a measure of a drug's biological activity expressed in terms of the dose required to produce a pharmacological effect of given intensity. ^[2] A highly potent drug (e.g., fentanyl, clonazepam, risperidone, benperidol, bumetanide) evokes a given response at low concentrations, while a drug of lower potency (e.g. morphine, alprazolam, ziprasidone, haloperidol, furosemide) evokes the same response only at higher concentrations. Higher potency does not necessarily mean greater effectiveness nor more side effects nor less side effects.

Types of potency

The International Union of Basic and Clinical Pharmacology (IUPHAR) has stated that "potency is an imprecise term that should always be further defined", ^[2] and lists of types of potency as follows:

Type of potency	Symbol	Definition
Effective dose	${\displaystyle {\ce {ED_{50}}}}$	It is the minimum dose or concentration of a drug that produces a biological response in 50% of a population being studied.
Median lethal dose	${\displaystyle {\ce {LD_{50}}}}$	For either drugs or toxins, it is a toxic unit that measures the minimum dose that causes death (lethal dose) in 50% of cases.
Median toxic dose	${\displaystyle {\ce {TD_{50}}}}$	It is the minimum dose at which toxicity occurs in 50% of cases.
Half maximal effective concentration	${\displaystyle {\ce {EC_{50}}}}$	It is a measure of the concentration of a drug, antibody or toxicant which induces a biological response halfway between the baseline and maximum after a specified exposure time. In other words, it can be defined as the concentration required to obtain a 50% effect. [3]
Half maximal inhibitory concentration	${\displaystyle {\ce {IC_{50}}}}$	It is a measure of the potency of a substance in inhibiting a specific biological or biochemical function.

Miscellaneous

Lysergic acid diethylamide (LSD) is one of the most potent psychoactive drugs known, with effects occurring at doses of as low as 20 μg. ^[4]

See also

• Reaction inhibitor § Potency

References

1. Miles AA, Perry EL (1953). "Biological potency and its relation to therapeutic efficacy". Bull World Health Organ. 9 (1): 1–14. PMC   2542104 . PMID   13082386.
2. Neubig RR, Spedding M, Kenakin T, Christopoulos A (December 2003). "International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. XXXVIII. Update on terms and symbols in quantitative pharmacology" . Pharmacological Reviews. 55 (4): 597–606. doi:10.1124/pr.55.4.4. PMID   14657418. S2CID   1729572.
3. "Introducing dose response curves". Graphpad Software. Archived from the original on 2012-07-30.
4. Nichols DE (October 2018). "Dark Classics in Chemical Neuroscience: Lysergic Acid Diethylamide (LSD)" (PDF). ACS Chem Neurosci. 9 (10): 2331–2343. doi:10.1021/acschemneuro.8b00043. PMID   29461039.

Further reading

• Harris, Robert (2012-10-09). "Formulating High Potency Drugs". Contract Pharma. Retrieved 2013-11-13.
• Walker MG, Page CP, Hoffman BF, Curtis M (2006). Integrated Pharmacology (3rd ed.). Mosby. ISBN   978-0-323-04080-8. OCLC   821705270.
• McCrackin, Carmen (2019). "New Research Exposes The 15 Most Dangerous Drugs". Addiction Center.
• "Drugs A to Z". U.S. National Institute on Drug Abuse. 2025. Archived from the original on June 12, 2022. Drugs A to Z gives basic information on drugs with addictive potential, including how they are used, how they make people feel, and their health effects, including risk for substance use disorder.