Editing Pharmacology (section)

===Pharmacodynamics===
{{More citations needed section|date=November 2023}}{{main|Pharmacodynamics}}
Pharmacodynamics is defined as how the body reacts to the drugs. Pharmacodynamics theory often investigates the [[binding affinity]] of [[ligand (biochemistry)|ligand]]s to their receptors. Ligands can be [[agonist]]s, partial agonists or [[Receptor antagonist|antagonists]] at specific receptors in the body. Agonists bind to receptors and produce a biological response, a partial agonist produces a biological response lower than that of a full agonist, antagonists have affinity for a receptor but do not produce a biological response.

The ability of a ligand to produce a biological response is termed [[Intrinsic activity|efficacy]], in a dose-response profile it is indicated as percentage on the y-axis, where 100% is the maximal efficacy (all receptors are occupied).

Binding affinity is the ability of a ligand to form a ligand-receptor complex either through [[Van der Waals force|weak attractive forces]] (reversible) or [[covalent bond]] (irreversible), therefore efficacy is dependent on binding affinity.

[[Potency (pharmacology)|Potency]] of drug is the measure of its effectiveness, [[EC50|EC<sub>50</sub>]] is the drug concentration of a drug that produces an efficacy of 50% and the lower the concentration the higher the potency of the drug therefore EC<sub>50</sub> can be used to compare potencies of drugs.

Medication is said to have a narrow or wide ''[[therapeutic index]],'' [[certain safety factor]] or ''[[therapeutic window]]''. This describes the ratio of desired effect to toxic effect. A compound with a narrow therapeutic index (close to one) exerts its desired effect at a dose close to its toxic dose. A compound with a wide therapeutic index (greater than five) exerts its desired effect at a dose substantially below its toxic dose. Those with a narrow margin are more difficult to dose and administer, and may require [[therapeutic drug monitoring]] (examples are [[warfarin]], some [[antiepileptic]]s, [[aminoglycoside]] [[antibiotics]]). Most anti-[[cancer]] drugs have a narrow therapeutic margin: toxic side-effects are almost always encountered at doses used to kill [[tumor]]s.

The effect of drugs can be described with [[Loewe additivity]] which is one of several common reference models.<ref name="Mehrad Babaei 2023"/>

Other models include the [[Hill equation (biochemistry)|Hill equation]], [[Cheng-Prusoff equation]] and [[Schild regression]].