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Definition
when a drug binds to the receptor and activates it to produce an effect
•Will have both Affinity and maximal Intrinsic activity
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Definition
when a drug binds to a receptor and prevents the action of an agonist, but does not have an action on its own
•Will have only Affinity but no Intrinsic activity
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Definition
when a drug activates a receptor to produce an effect in the opposite direction to that of the agonist
•Will have Affinity and negative Intrinsic activity
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Definition
when a drug binds to the receptor and activates it but produces a submaximal effect (by antagonising the full effect of the agonist)
•Will have Affinity but sub maximal Intrinsic activity (between 0 and 1)
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Definition
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It is the ability of a drug to bind to the receptor (just bind)
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Definition
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It is the ability of a drug to activate a receptor following receptor occupation. (i.e elicit a response)
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Term
| Down regulation of receptors? |
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Definition
| occurs after chronic stimulation of receptors by an agonist |
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Term
| Upregulation of receptors? |
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Definition
| Occurs after chronic administration of an antagonist over a long period of time |
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Term
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Definition
•Gradual reduction in response to drugs is called as tolerance
•Requirement of higher dose to produce a given response
•It occurs over a period of time
Can be either due to enhanced clearance of drug or down regulation of receptors
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Term
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Definition
•Rapid desensitization to a drug produced by inoculation with a series of small frequent doses.
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Term
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Definition
is the maximal response produced by a drug
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Definition
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•is a measure of how much drug is required to elicit a given response
•The lower the dose required to elicit given response, the more potent the drug is
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Term
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Definition
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•It is the dose of the drug at which it gives 50% of the maximal response
•A drug with low ED50 is more potent than a drug with larger ED50
SAME AS POTENCY (the more left on the graph the more potent)
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Term
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Definition
| (abbreviation for "Lethal Dose, 50%") or median lethal dose of a toxic substance is the dose required to kill half the members of a tested population |
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Term
| TI / Therapeutic Window or Range |
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Definition
TI = LD50/ED50, the higher the TI the safer the drug.
TW = describes the dosage range between the minimum effective therapeutic concentration or dose, and the minimum toxic concentration or dose.
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Term
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Definition
1.Additive effect: the effect of two drugs are in the same direction and simply add up.
•Effect of drug 1+1 = 2
2.Supraadditive effect (potentiation): the effect of combination is greater than the individual effect of the components.
•Effect of drug 1 + 1 = 3
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Term
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Definition
two drugs act on different receptors or by different mechanisms, but have opposite,
e.g ..bee sting..histamine released bronchial constriction vasodilatation and adrenaline given leads to bronchodilation and vasoconstriction on bronchial smooth muscle and BP
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Term
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Definition
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•Competes with agonist in reversible fashion for same receptor site
•Necessary to have higher concentration of agonist to achieve same response
(look at graph slide 80 PD lecture)
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Term
| Noncompetitive antagonism |
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Definition
•Antagonist binds to a site different to that of an agonist
•No matter how much agonist -- antagonism cannot be overcome
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Term
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Definition
•The concentration of the drug required to bind 50% of the receptor sites is called as Kd
•It is the measure of the affinity of the drug molecule
•Smaller the Kd greater the affinity of the drug for its receptor
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Term
| Spare receptors, KD and EC50 |
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Definition
•KD is the concentration of the agonist at which 50% of the receptors are occupied
•If the number of receptors increase many fold (spare receptors) THEN:
•A much lower concentration of agonist is sufficient to produce 50% of maximal response (EC50)
•Occupation of spare receptors is determined by comparing the EC50 with Kd
•If EC50 is less than Kd, spare receptors are said to exist
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Term
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Definition
| Ach + nicotinic receptor = entry of Na+ |
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Term
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Definition
| 7 transmembrane segments, 3- intracellular loops and an intracellular carboxy-terminal tail.... activity is mediated via interaction with a number of GTP bound proteins |
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Definition
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•These receptors bind their ligand in the cytoplasm and translocate to the nucleus. e.g. steroids |
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Term
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Definition
•Contain an extracellular ligand binding domain, one transmembrane spanning segment, and an intracellular tyrosine kinase domain.
•Binding of a ligand to the extracellular domain causes dimerization of the receptor and stimulates a tyrosine kinase activity within the intracellular domain. e.g. Insulin & cytokines
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Term
| Quantal dose response curves |
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Definition
•a study of the therapeutic and lethal effects of a new drug in preclinical studies
•used to generate information regarding the margin of safety (Therapeutic index)
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Definition
based on chemical properties resulting in an inactive product.
•E.g. chelating agents complex metals (used in heavy metal poisoning) I.e antacids.. Alkalize the acidic stomach
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Term
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Definition
based on physical property of a drug.
•E.g. activated charcoal adsorbs alkaloids and prevents their absorption (in alkaloid poisoning)
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