Editing Drug interaction (section)

== Interactions based on pharmacodynamics ==

[[Pharmacodynamic]] interactions are the drug–drug interactions that occur at a [[Biochemistry|biochemical]] level and depend mainly on the biological processes of organisms. These interactions occur due to action on the same targets; for example, the same receptor or [[Cell signaling|signaling pathway]].

[[File:Agonist Antagonist.svg|300px|thumb|Effects of the competitive inhibition of an agonist by increases in the concentration of an antagonist. A drug's potency can be affected (the response curve shifted to the right) by the presence of an antagonistic interaction.]]
Pharmacodynamic interactions can occur on protein [[Receptor (biochemistry)|receptors]].<ref>{{cite web
 |url          = http://canal-h.net/webs/sgonzalez002/Farmaco/INTERACCIONES.htm
 |title        = Interacciones Farmacológicas
 |access-date  = 1 January 2009
 |author       = S Gonzalez
 |language     = es
 |archive-url  = https://web.archive.org/web/20090122214121/http://canal-h.net/webs/sgonzalez002/Farmaco/INTERACCIONES.htm
 |archive-date = 2009-01-22
 |url-status     = dead
}}</ref>  Two drugs can be considered to be ''homodynamic'', if they act on the same receptor. Homodynamic effects include drugs that act as (1) pure [[agonists]], if they bind to the main [[locus (genetics)|locus]] of the [[Receptor (biochemistry)|receptor]], causing a similar effect to that of the main drug, (2) partial [[agonists]] if, on binding to a secondary site, they have the same effect as the main drug, but with a lower intensity and (3) [[antagonist]]s, if they bind directly to the receptor's main locus but their effect is opposite to that of the main drug. These may be c''ompetitive antagonists'', if they compete with the main drug to bind with the receptor. or u''ncompetitive antagonists,'' when the antagonist binds to the receptor irreversibly. The drugs can be considered ''heterodynamic'' competitors, if they act on distinct receptor with similar [[Signaling pathway|downstream pathways]].

The interaction my also occur via signal transduction mechanisms.<ref name="Medico">[http://www.elmedicointeractivo.com/farmacia/temas/tema1-2/farmaa3.htm ''Curso de Farmacología Clínica Aplicada'', in El Médico Interactivo] {{webarchive|url=https://web.archive.org/web/20090831065941/http://www.elmedicointeractivo.com/farmacia/temas/tema1-2/farmaa3.htm |date=2009-08-31 }}</ref> For example, [[Hypoglycemia|low blood glucose]] leads to a release of [[catecholamine]]s, triggering [[symptom]]s that hint the organism to take action, like consuming sugary foods. If a patient is on [[insulin]], which reduces blood sugar, and also [[Beta blocker|beta-blockers]], the body is less able to cope with an insulin overdose.