Question

1. Explain the agonist-to-antagonist spectrum of action of psychopharmacologic agents. Describe what an agonist, partial agonist, antagonist, and inverse agonist are. List one or two medications in each of these categories.
2. What is a G-protein-linked receptor?
3. Explain how this information may impact the way you prescribe medications to patients. Include a specific example of a situation or case with a client in which you must be aware of the medication’s action.

Answer 1

Agonist is a substance or drug which binds with the recepter and produce same cellular effect as that of naturally occuring neurotransmitters and hormones ( mimiking their action) , example : salbutamol : beta 2 agonist -produces smooth muscle relaxation

Antagonist will interact with the recepter and will block the effects of naturally occuring hormones and neurotransmitters, example : Ranitidine : Antagonist to Histamine H2 receptor - reduces the acid secretion in stomach

Partial agonist : substances that can activate receptors but cannot elicit the maximum response from the receptor system , example :tramadol is a partial agonist of mu receptor

Inverse agonist:substances which binds to the same binding site of the agonist in the receptor and produces an oppisite pharmacological effect of a receptor agonist , example : naloxane is an inverse agonist ( mu opiod receptor )

G- Protein linked receptor: Consists of 7 transmembrane receptors and a G protein , the transmembrane receptors are located on the cell wall, these receptors bind to the extracellular substances and will transmit signals from the substances to the intracellular molecule ( G protein )

psycopharmacological agents the anatgonist and agonist will be acting on the same recptors thereby producing opposite effect

L dopa ( used to treat parkinsonism)is a Dopamin Agonist where as seroquel (used in the treatment of bipolar disorder )is a Dopamin antagonist

Neurotransmitters GABA full agonist - benzodiazapines

Seratonin - full antagonist - antidepressant

While prescribing medication the importance of agonist and antagonist is that of we are prescribing a certian drug we must make sure that the patient is not having any antagonist drug because the effect of agonist drug will therfore be nullified by the antagonist drug and the patient will get no benifit out of it so it is necessary that a doctor be aware of what an agonist and antagonistic effect of a drug

If we use two agonist it will have a synergestic effect and the total response that we will get will be maximum , where as if we use an agonist and an antagonist the antagonistic effect will result in a decreased response

Example. Beta agonist are used in the treatment of asthama , copd -salbutamol - smooth muscle relaxant action , if a beta blocker is given to the same patient for treatment to hypertension it would result in greater difficulty