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Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as ''
effectiveness Effectiveness is the capability of producing a desired result or the ability to produce desired output. When something is deemed effective, it means it has an intended or expected outcome, or produces a deep, vivid impression. Etymology The orig ...
'', and it has often been used synonymously, although in
pharmacology Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
a distinction is now often made between efficacy and effectiveness. The word ''efficacy'' is used in
pharmacology Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
and
medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), skills (proced ...

medicine
to refer both to the maximum response achievable from a
pharmaceutical drug A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and binders. Aspir ...
in research settings, and to the capacity for sufficient therapeutic effect or beneficial change in clinical settings.


Pharmacology

In pharmacology, efficacy () is the maximum response achievable from an applied or dosed agent, for instance, a small molecule drug.
Intrinsic activityImage:Efficacy spectrum.png, 320px, Efficacy spectrum of receptor ligands. Intrinsic activity (IA) and efficacy refer to the relative ability of a drug-receptor (biochemistry), receptor complex to produce a maximum functional response. This must be ...
is a relative term for a drug's efficacy relative to a drug with the highest observed efficacy. It is a purely descriptive term that has little or no mechanistic interpretation. In order for a drug to have an effect, it needs to bind to its target, and then to affect the function of this target. The target of a drug is commonly referred to as a , but can in general be any chemically sensitive site on any molecule found in the body. The nature of such binding can be quantified by characterising how tightly these molecules, the drug and its receptor, interact: this is known as the
affinity Affinity may refer to: Commerce, finance and law * Affinity (law) In law and in cultural anthropology Cultural anthropology is a branch of anthropology Anthropology is the scientific study of human Humans (''Homo sapiens' ...
. Efficacy, on the other hand, is a measure of the action of a drug once binding has occurred. The maximum response, , will be reduced if efficacy is sufficiently low. The definition of efficacy has been object for discussion. The only way in which absolute measures of efficacy have been obtained is by single ion channel analysis of ligand gated ion channels. It is still not possible to do this for G protein-linked receptors. In the case of the glycine receptor and the nicotinic acetylcholine receptor (muscle type), it has been proposed by Sivilotti ''et al''. that opening of the ion channel involves two steps after agonist is bound. Firstly a conformation change to a higher affinity (but still shut) form, followed by the conformation change from shut to open. It was found that partial agonism results from deficiency in the first step, and that the opening and shutting steps are essentially the same for both full and partial agonists. This has been confirmed and extended by Sine and colleagues (2009). The implication of this work is that efficacy has to be defined by at least two equilibrium constants (or, more generally, by four rate constants). The combined influences of affinity and efficacy determine how effectively a drug will produce a biological effect, a property known as potency.


Medicine

In medicine, efficacy is the capacity for beneficial change (or
therapeutic effect Therapeutic effect refers to the response(s) after a treatment of any kind, the results of which are judged to be useful or favorable. This is true whether the result was expected, unexpected, or even an unintended consequence. An adverse effect (i ...
) of a given intervention (for example a drug,
medical device A medical device is any device intended to be used for medical purposes. Significant potential for hazard A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would allow them, e ...
,
surgical procedure Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical or dental specialty that uses operative manual and instrumental techniques on a person to investigate or t ...

surgical procedure
, or a
public health Public health has been defined as "the science and art of preventing disease", prolonging life and improving quality of life Quality of life (QOL) is defined by the World Health Organization The World Health Organization (WHO) is a s ...

public health
intervention). Establishment of the efficacy of an intervention is often done relative to other available interventions, with which it will be compared. Specifically, efficacy refers to "whether a drug demonstrates a health benefit over a placebo or other intervention when tested in an ideal situation, such as a tightly controlled clinical trial." These studies focus on a primary parameter to be shown statistically different between placebo and intervention groups. Comparisons of this type are called 'explanatory'
randomized controlled trial A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into Causality, cause-and- ...
s, whereas 'pragmatic' trials are used to establish the ''effectiveness'' of an intervention regarding also non-specific parameters. Effectiveness refers to "how the drug works in a real-world situation", and is "often lower than efficacy because of interactions with other medications or health conditions of the patient, sufficient dose or duration of use not prescribed by the physician or followed by the patient, or use for an off-label condition that had not been tested."


Theology


Scripture

In
Protestant Theology Protestantism is a form of Christianity Christianity is an Abrahamic religions, Abrahamic Monotheism, monotheistic religion based on the Life of Jesus in the New Testament, life and Teachings of Jesus, teachings of Jesus, Jesus of Nazareth. I ...
(esp. in
Lutheran Lutheranism is one of the largest branches of Protestantism that identifies with the teachings of Jesus Christ and was founded by Martin Luther, a 16th-century German monk and Protestant Reformers, reformer whose efforts to reform the theology ...
but also in
Calvinist Calvinism (also called the Reformed tradition, Reformed Christianity, Reformed Protestantism, or the Reformed faith) is a major branch of Protestantism Protestantism is a form of Christianity Christianity is an , based on the a ...
doctrine) ''efficacy'' is an attribute of
Scripture Religious texts, also known as scripture, scriptures, holy writ, or holy books, are the texts which various religious traditions consider to be sacred Sacred describes something that is dedicated or set apart for the service or worship of ...
. The efficacy of Scripture means that it is united with the power of the Holy Spirit and with it, not only demands, but also creates the acceptance of its
teaching Education is the process of facilitating learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, attitudes, and preferences. The ability to learn is possessed ...
and that this teaching produces faith and obedience. Efficacy further means that Holy Scripture is not a dead letter, but rather, the power of the Holy Spirit is inherent in it and that Scripture does not compel a mere intellectual assent to its doctrine, resting on logical argumentation, but rather it creates the living agreement of faith. The
Smalcald Articles The Smalcald Articles or Schmalkald Articles (german: Schmalkaldische Artikel) are a summary of Lutheran Lutheranism is one of the largest branches of Protestantism that identifies with the teachings of Martin Luther, a 16th-century German Prote ...
affirm, "in those things which concern the spoken, outward Word, we must firmly hold that God or grace to no one, except through or with the preceding outward Word." The
Formula of Concord Formula of Concord (1577) (German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * ...
teaches that when humans reject the calling of the Holy Spirit, it is not a result of the Word being less efficacious. Instead, contempt for the
means of grace The means of grace in Christian theology Christian theology is the theology of Christianity, Christian belief and practice. * help them better understand Christian tenets * make comparative religion, comparisons between Christianity and other tr ...
is the result of "the perverse will of man, which rejects or perverts the means and instrument of the Holy Ghost, which God offers him through the
call Call or Calls may refer to: Arts, entertainment, and media Games * Call, a type of betting in poker * Call, in the game of contract bridge, a bid, pass, double, or redouble in the bidding stage Music and dance * Call (band), from Lahore, Pakis ...
, and resists the Holy Ghost, who wishes to be efficacious, and works through the
Word In linguistics Linguistics is the scientific study of language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed language, sign language) and writing. Most lang ...
..."Solid Declaration, article xii, "Election", par. 41
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Prayer


See also

*
Average treatment effect The average treatment effect (ATE) is a measure used to compare treatments (or interventions) in randomized experiments, evaluation of policy interventions, and medical trials. The ATE measures the difference in mean There are several kinds of ...
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Efficiency (disambiguation) Efficiency Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, ...
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Placebo (origins of technical term) A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like Saline (medicine), saline), sham surgery, and other procedures. In general ...
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Potency (pharmacology) In the field of pharmacology Pharmacology is a branch of , and concerned with or action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemical or physiological ef ...
*
Pragmatic clinical trial A pragmatic clinical trial (PCT), sometimes called a practical clinical trial (PCT), is a clinical trial Clinical trials are experiments or observations done in clinical research. Such prospective biomedical or behavioral research studies on h ...
*
Self-efficacy Self-efficacy, a concept originally proposed by the psychologist Albert Bandura Albert Bandura (; born December 4, 1925) is a Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be r ...
*
Vaccine efficacy Vaccine efficacy is the percentage reduction of disease in a vaccinated group of people compared to an unvaccinated group, using the most favorable conditions. Vaccine efficacy was designed and calculated by Greenwood and Yule in 1915 for the cho ...


References

{{Pharmacology Medical terminology Pharmacodynamics