The negative logarithm to base 10 of the EC50 of an agonist is called pEC50 or pD2 (old term). It indicates the potency of an agonist but not its efficacy, the higher pD2=small EC50, reflects higher potency of the agonist.

How do you calculate pD2?

pD2 value (pD2 = -log EC50) was calculated using indometazine in guinea pig trachea. This bioassay record (AID 80765) reports results from the above primary citation.

What is a pA2 value?

In the field of biochemistry, a pA2 value determines the important relationship between two drugs “competing” for effect on the same receptor. … The pA2 value indicates the concentration of antagonist when double the agonist is required to have the same effect on the receptor as when no antagonist is present.

Is pD2 the same as EC50?

pD2. pD2 is the negative logarithm of an EC50 or IC50 value.

What is EC50 value?

Half maximal effective concentration (EC50) refers to the concentration of a drug, antibody or toxicant which induces a response halfway between the baseline and maximum after a specified exposure time. … EC50 is a measure of concentration, expressed in molar units (M), where 1 M is equivalent to 1 mol/L.

Does phentolamine decrease heart rate?

1 Intravenously administered phentolamine provoked immediate decreases in diastolic blood pressure but increases in heart rate and cardiac output.

What does a Schild plot show?

Schild plot A graph of log (concentration ratio – 1) against log (antagonist concentration). An example is shown in Fig. C. The intercept on the log concentration axis is equal to the pA2 value, while the slope gives information about the nature of the antagonism.

What is DRC pharmacology?

“DRUG RESPONSE CURVE & THERAPEUTIC” it’s a topic in which detail information about How Drug Response when taken in body & effect of various drugs on body with there Response Curve is Given.

What does a non competitive antagonist do?

A non-competitive antagonist can prevent the action of an agonist without any effect on the binding of the agonist to the receptor. An insurmountable antagonist can reduce the maximum effect of the agonist, and this inhibitory effect is not affected by increasing agonist concentration.

What is IC value?

The IC50 value is that concentration of a drug that reduces the activity (or binding) of another drug to an enzyme by 50%. Under certain conditions it can used to express the affinity of the enzyme inhibitor. Drug Interactions. drug-receptor interaction.

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What does EC90 mean?

The EC90 was calculated as the concentration of drug that increased the percentage of formazan production in drug treated, virus infected cells to 50% of that produced by drug free uninfected cells on human rhinovirus-2.

What is the difference between KD and EC50?

The EC50 indicates how much of a drug is needed to achieve 50% of the maximum response. The more potent a drug, the smaller the EC50 will be. This value is obtained from a dose-response curve. Kd is the dissociation constant and can only be obtained from a binding curve/fractional occupancy curve).

Does pA2 value have units?

pA2 is the negative logarithm of the concentration of antagonist needed to shift the dose response curve by a factor of 2. … The units are the negative log of whatever units you used to enter concentrations as column titles on the data table.

Is pA2 the same as KB?

In experiments on isolated organs and tissues, the calculation of dissociation constant (KB) and pA2 value (a negative logarithm of KB when the slope of the Schild’s plot is exactly 1) of an antagonist is considered to be an indirect measure of antagonist’s affinity for its receptors.

Where is pA2 in Schild plot?

The pA2 is defined as the negative common logarithm of B which produces a dose-ratio of 2; hence, pA2 = -log B = -log KB = 10g(1jKB). Since IjKB is the affinity constant, the pA2 may be viewed as a measure of affinity.

Is a high IC50 good?

IC50 is the dose of the substance which inhibits the proliferation of half of the cells. It does not necessarily need to kill the cells. If you find high IC50, this means that the cell line is more resistant to drug1 than drug 2. … Then, you can suspect from other cell deaths, too.

Why is EC50 useful?

The EC50 (or ED50) is the concentration (or dose) effective in producing 50% of the maximal response and is a convenient way of comparing drug potencies.

What is EC50 in toxicology?

Terminology: EC50(50% Effective Concentration) The median effective concentration (EC50) is the concentration of a substance in an environmental medium expected to produce a certain effect in 50% of test organisms (usually planktonic crustacean Daphnia) in a given population under a defined set of conditions.

What does the Schild equation show?

Specifically, a method (Schild analysis) first described almost 60 years ago allows us to determine the equilibrium constant for binding of a competitive antagonist acting at a particular receptor (Schild, 1949; Arunlakshana and Schild, 1959).

What is the Cheng Prusoff equation?

The Cheng-Prusoff equation defines the theoretical relation- ship between the measured IC50 for a competitive inhibitor of given Ki, the concentration of labeled ligand, and the KD of the ligand-receptor interaction.

What is irreversible binding?

An irreversible antagonist is a type of antagonist that binds permanently to a receptor, either by forming a covalent bond to the active site, or alternatively just by binding so tightly that the rate of dissociation is effectively zero at relevant time scales.

Does phentolamine increase cardiac output?

Phentolamine is a competitive α-adrenergic receptor antagonist with greater affinity for the α1- than the α2-receptor subtype. Systemic vascular resistance is decreased, whereas heart rate, cardiac output, and myocardial oxygen demand are increased during phentolamine administration.

What class of drug is phentolamine?

Phentolamine belongs to a group of medications called vasodilators. These drugs work by causing blood vessels to expand and allow more blood to flow through them.

What type of drug is phentolamine?

Phentolamine is an alpha-Adrenergic Blocker. The mechanism of action of phentolamine is as an Adrenergic alpha-Antagonist.

What are antagonists used for?

Competitive antagonists are used to prevent the activity of drugs, and to reverse the effects of drugs that have already been consumed. Naloxone (also known as Narcan) is used to reverse opioid overdose caused by drugs such as heroin or morphine.

How do antagonists work?

An antagonist is a type of ligand or drug that avoids or dampens a biological reaction. Upon binding to the receptor, it does not activate. Rather it tends to block the particular receptor. Sometimes, they are also referred to as blockers such as alpha-blockers or beta-blockers.

What are examples of antagonists?

• Darth Vadar is the main antagonist of Luke Skywalker in Star Wars.
• Mr. …
• The wolf is the antagonist in “The Three Little Pigs.”
• MacDuff is an antagonist of Macbeth in Macbeth.
• In Dr. …
• In the movie Aladdin, Jafar is the antagonist.

What does potency mean in pharmacology?

Results: Potency is an expression of the activity of a drug in terms of the concentration or amount of the drug required to produce a defined effect, whereas clinical efficacy judges the therapeutic effectiveness of the drug in humans.

What is the full form of DRC?

Democratic Republic of the Congo.

How is drug potency calculated?

Relative Potency=DoseStandard sample / DoseTest sample when the 2 doses produce the same effect. Note that the relative potency is NOT dose specific. It is not quoted as the potency for a certain effect, but just as a ratio when the two samples produce the same effect (of any magnitude).

How is IC50 value calculated?

The simplest estimate of IC50 is to plot x-y and fit the data with a straight line (linear regression). IC50 value is then estimated using the fitted line, i.e., Y = a * X + b, IC50 = (0.5 – b)/a.