Schild equation

Schild equation is a mathematical model used in the field of pharmacology to quantify the effect of antagonists on the action of agonists in drug-receptor interactions. Named after the British pharmacologist P.A. Schild, this equation is a fundamental tool in the study of drug interactions and receptor theory.

Overview

The Schild equation is derived from the Cheng-Prusoff equation and is used to determine the potency of an antagonist by measuring its ability to inhibit the action of an agonist. The equation is expressed as:

r = [B]/(K_B(1+[A]/K_A))

where:

• r is the dose ratio (the concentration of agonist in the presence of antagonist divided by the concentration of agonist in the absence of antagonist)
• [B] is the concentration of antagonist
• K_B is the equilibrium dissociation constant of the antagonist
• [A] is the concentration of agonist
• K_A is the equilibrium dissociation constant of the agonist

Applications

The Schild equation is widely used in pharmacology to study the effects of drugs on the body. It allows researchers to quantify the potency of an antagonist and to compare the effectiveness of different drugs. This information is crucial in the development of new medications and in understanding how drugs interact with the body.

Limitations

While the Schild equation is a powerful tool, it has its limitations. It assumes that the antagonist does not change the affinity of the agonist for the receptor, which is not always the case. Furthermore, it assumes that the antagonist and agonist bind to the same site on the receptor, which may not be true for all drug-receptor interactions.

See also

• Cheng-Prusoff equation
• Pharmacodynamics
• Receptor theory