What is activity and Fugacity?
The activity of pure substances in condensed phases (solid or liquids) is normally taken as unity (the number 1). Activity depends on temperature, pressure and composition of the mixture, among other things. For gases, the activity is the effective partial pressure, and is usually referred to as fugacity.
What is the effective concentration?
In pharmacology, an effective dose (ED) or effective concentration (EC) is a dose or concentration of a drug that produces a biological response. The term effective dose is used when measurements are taken in vivo, while the term effective concentration is used when the measurements are taken in vitro.
What is the minimum toxic concentration?
Minimum toxic concentration (MTC) is the minimum concentration in which toxicity usually occurs. If you have a low dose for the drug to start working (MEC) and a high dose at which the drug is toxic (MTC) you have a wide window in which the drug can safely be used (TW)
What is a good IC50 value?
Generally, less than 10 micromolar concentration of a drug in plasma is accepted because higher than 10 uM of a drug inhibit necessary enzymes. The most of the drugs on the market have less than 10 micromolar therapeutic plasma concentrations.
What is the minimum effective concentration?
Minimum effective concentration (MEC) is the minimum plasma concentration of a drug needed to achieve sufficient drug concentration at the receptors to produce the desired pharmacologic response, if drug molecules in plasma are in equilibrium with drug molecules in the various tissues (Figure 1.3).
What is toxic concentration?
The concentration at which a particular substance produces a toxic effect. From: toxic concentration in A Dictionary of Environment and Conservation » Subjects: Science and technology — Environmental Science.
What is ED50 and TD50?
Therapeutic Index = TD50 / ED50. ED50 is the dose required to produce a therapeutic effect in 50% of the population; TD50 is the dose required to produce a toxic effect in 50% of the population; both are calculated from dose–response curves.
How is ED50 calculated?
The ED50 is the dose required to achieve 50% of the desired response in 50% of the population. It is thus calculated from a dose–response curve by dropping a line on the dose axis where 50% of the desired response is seen. As with LD50 and TD50, ED50 is usually reported in regulatory submissions of a new drug.
What is EC50 value?
Half maximal effective concentration (EC50) refers to the concentration of a drug, antibody or toxicant which induces a response halfway between the baseline and maximum after a specified exposure time.
Which drug is more potent?
The term potency is used as a comparative term for distinguishing which agonist has a higher affinity for a given receptor (Figure 2). The drug which can produce an effect at lower drug concentrations is “more potent” (in Figure 3, Drug A is the most potent, and Drug D is the least potent).
What is the full form of TD50?
In toxicology, the median toxic dose (TD50) of a drug or toxin is the dose at which toxicity occurs in 50% of cases. The type of toxicity should be specified for this value to have meaning for practical purposes.
What is lc50?
LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material.
What is the difference between LD50 and TD50?
LD50 is the amount of a toxic substance which, when given all at once, causes the death of 50% of a group of test organisms. TD stands for Toxic Dose. TD50 is the median toxic dose of a substance at which toxicity occurs in 50% of the cases.
What is a safe therapeutic index?
Therapeutic Index The TI is a statement of relative safety of a drug. It is the ratio of the dose that produces toxicity to the dose needed to produce the desired therapeutic response. To overcome this deficiency, toxicologists often use another term to denote the safety of a drug: the Margin of Safety .
Which therapeutic index is the safest?
A ratio that compares the blood concentration at which a drug becomes toxic and the concentration at which the drug is effective. The larger the therapeutic index (TI), the safer the drug is.
What is a high therapeutic index?
A high therapeutic index (TI) is preferable for a drug to have a favorable safety and efficacy profile. In general, it is the exposure of a given tissue to drug (i.e. drug concentration over time), rather than dose, that drives the pharmacological and toxicological effects.
What is half life of a drug?
What is a drug’s half-life? The half-life of a drug is the time it takes for the amount of a drug’s active substance in your body to reduce by half. This depends on how the body processes and gets rid of the drug.
Which drug has the longest half life?
However, there are numerous other drugs with very long half-life, examples are mefloquine 14–41 days (25), amiodarone 21–78 days (26), and oritavancin 393 h (27). Furthermore, what can be called “long half-life” is always relative to the length of the sampling period.
What is Half Life Cycle?
Half-life (symbol t1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.
How do half lives work?
Half-life is used to describe exponential decay. In one half-life period, on average, half of the C14 atoms would decay. So one would expect that if you start with four C14 atoms, you would after one half life have two, and after another half life only one would remain.
What is the formula for Half-Life in chemistry?
The half-life of a reaction is the time required for the reactant concentration to decrease to one-half its initial value. The half-life of a first-order reaction is a constant that is related to the rate constant for the reaction: t1/2 = 0.693/k.
Why is it called a half-life?
It’s easy misinterpret half-life to mean “one half of the time it takes for whatever atoms you’re looking at to decay,” but it actually means “the length of time it takes for one half of the atoms you’re looking at to decay.” The measurement is useful in radiometric dating, says Dee, because exponential decay means “it …
What is the half-life symbol called?
λ
What is this symbol λ?
Lambda (uppercase/lowercase Λ λ) is a letter of the Greek alphabet. It is used to represent the “l” sound in Ancient and Modern Greek. Letters that came from it include the Roman L and Cyrillic Л.
Why did the Spartans use the Lambda?
The lambda was adopted as the symbol of Laconia (the region of Greece where Sparta is located) and Lacedaemon (the ancient name for the city) in the late 5th century BC. Shields were treated as family heirlooms passed down from father to son among the Spartans and were considered more valuable than even their weapons.
What does 5 half lives mean?
Generally it is considered that it takes 5.5 half-lifes for a drug to be removed from the body, in that it is considered to no longer have a clinical effect. So for Ambien it would take approximately 11 hours (2 hours X 5.5) to be eliminated from your body.