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Category: Ed Treatment Area Coordinator | Author: admin 08.01.2016
A drug capable of combining with receptors to initiate drug actions; it possesses affinity and intrinsic activity. Affinity and intrinsic activity of a drug are intimately related to its chemical structure (a€?receptor selectivitya€?). Potency refers to the concentration (EC50) or dose (ED50) of a drug required to produce 50% of its maximal effect; the lower the dose required to produce a given effect, the higher the potency. The maximal effect Efficacy of a drug may be limited by its propensity to produce a toxic effect. Select an end point or a specified effect and determine the number of individuals at each dose who show the specified effect (a€?all-or-nonea€?).
The dose of a drug required to produce a specified intensity of effect in 50% of individuals. An antagonist may increase the number of receptors in a critical cell or tissue by preventing down-regulation caused by an endogenous agonist. Exposure to an agonist ligand may result in a€?down-regulationa€?---an actual decrease in number of receptors. The relationship between the doses of a drug required to produce undesired and desired effects The therapeutic index (TI) of a drug reflects its selectivity.
The Psychopharmacology Institute has created a compilation of guidelines on bipolar disorder.
Gamma amino butyric acid (GABA) is an inhibiting neurotransmitter that is present on human brains.
This opening leads to a increased conductance to cloride ions, which produces membrane hiperpolarization, this induces a neuronal inhibition. The binding of benzodiazepines to the GABA-A receptor increases the affinity of gamma amino butyric acid (GABA) and its receptor, thereby increasing the opening frecuency of GABA-A receptor.As a consequence of this, BENZODIAZEPINES POTENTIATE GABAERGIC NEUROTRANSMISSION. The following video is a short overview on the pharmacological basis of SSRIs side effects. 5-HT2A and 2C receptors are hypothetically involved in agitation, anxiety and panic attacks. The concept of therapeutic index refers to the relationship between toxic and therapeutic dose. The therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response in a population of individuals.
Where: TD50 is the dose of drug that causes a toxic response in 50% of the population and ED50 is the dose of drug that is therapeutically effective in 50% of the population. Both ED50 and TD50 are calculated from QUANTAL DOSE RESPONSE CURVES, which represent the frequency with which each dose of drug elicits the desired response or toxic effect in the population.
The dose required to cause a therapeutic effect (positive response) in 50% of a population is the ED50.

Glutamate neurotransmission plays an important role in a number of physiologic and pathophysiologic processes. There are big expectations in the neuropharmacology field about the possible clinical applications of novel agents acting on these receptors. Glutamate receptors are divided into two subgroups: ionotropic (ligand-gated ion channels) and metabotropic (G protein-coupled receptors).
These receptors act as cation-selective channels, when activated they allow the flow of Na+ , K+ and Ca2+. Ionotropic glutamate receptors can be subdivided into three subtypes, according to their activation by selective agonists such as NMDA, AMPA and kainate.
NMDA receptors are ligand-gated ion channels, with a primary glutamate-binding site and an allosteric glycine-binding site.These receptors consist of multisubunit oligomeric transmembrane complexes. Three events need to occur simultaneously in order to activate NMDA receptors: binding of glutamate and glycine (which acts as cotransmitter) and membrane depolarization. These receptors regulate fast excitatory postsynaptic depolarization at glutamatergic synapses. Kainate receptors are expressed throughout the CNS, particularly in the hyppocampus and cerebellum where they play a role in both pre- and postsynaptic neurotransmission.
Metabotropic glutamate receptors (mGluR) are seven transmembrane-spanning proteins that exert their actions through G protein signalling cascades. Recent findings suggest that groups II and III might be located presynaptically, where they function as autoreceptors to block glutamate release.
Group I metabotropic glutamate receptors may be located postsynaptically, where they hypothetically enhance excitatory glutamatergic neurotransmission. Here you have a list of opinions about Therapeutic index and you can also give us your opinion about it. You will see other people's opinions about Therapeutic index and you will find out what the others say about it. The therapeutic index (TI) (also referred to as therapeutic window or safety window or sometimes as therapeutic ratio) is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity.
In the early days of pharmaceutical toxicology, TI was frequently determined in animals as lethal dose of a drug for 50% of the population (LD50) divided by the minimum effective dose for 50% of the population (ED50). For many drugs, there are severe toxicities that occur at sublethal doses in humans, and these toxicities often limit the maximum dose of a drug. In the image below, you can see a graph with the evolution of the times that people look for Therapeutic index. Thanks to this graph, we can see the interest Therapeutic index has and the evolution of its popularity. You can leave your opinion about Therapeutic index here as well as read the comments and opinions from other people about the topic.

5) Cell-surface receptors coupled to an effector enzyme by G proteins: Altered intracellular concentrations of “second messengers”. Affinity and intrinsic activity of a drug are intimately related to its chemical structure (“receptor selectivity”). This practical guide from the Psychopharmacology Institute summarizes the essentials for prescribers. Flavio Guzman, from the Psychopharmacology Institute, recently published a new multimedia tutorial on the mechanism of action and formulations of methylphenidate. This means that for some patients, a single SSRI at optimal doses is not enough to achieve remission. The FDA warned about the risk of QT prolongation with high doses of citalopram, but not escitalopram. As shown in the animation, gamma amino butyric acid promotes opening of a postsynaptic receptor, the GABA-A receptor. This pharmacodynamic parameter is relevant to clinical practice because it determines how safe (or toxic) a drug is.
Some examples of positive responses include: relief of headache for an antimigraine drug, increase in heart rate of at least 20 bpm for a cardiac stimulant, or 10 mmHg fall in diastolic blood pressure for an antihypertensive. UNLIKE GRADED DOSE-RESPONSE GRAPHS, DATA FOR QUANTAL DOSE-RESPONSE CURVES IS OBTAINED FROM MANY INDIVIDUALS. Activation of glutamate receptors occurs in pathways involved in pain, neurotoxicity and memory formation. Some of the conditions that might benefit from future glutamatergic drugs include: hyperalgesia, stroke, epilepsy and schizophrenia. A higher therapeutic index is preferable to a lower one: a patient would have to take a much higher dose of such a drug to reach the toxic threshold than the dose taken to elicit the therapeutic effect. And below it, you can see how many pieces of news have been created about Therapeutic index in the last years. When NMDA receptors are activated, Mg2+ ions are removed from their location, allowing the influx of Ca+2 ions. Therefore, activation of presynaptic group II and III mGLURs may inhibit glutamatergic excitatory neurotransmission.
In contrast, in a drug development setting TI is calculated based on plasma exposure levels.

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