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Hey Guys,

I have a question which I am not able to find exact accuracy anywhere, Can someone help me out with the below question?

If an extract is given i.p. and the effect is measured in blood by estimating the biological effect of the extract in diseased mice, can the intensity of effect over time be termed as bioavailability?

Thanks,
Sanjit
 

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You need to clear three terms up, bioavailability, efficacy and potency.


Bioavailability is the fraction of drug that reaches the systemic circulation. meaning the amount of drug given to a patient that will actually be found circulating in his blood.

For eg, if a drug is given via intravenous route, all of the drug will be found in the patient's systemic circulation i.e. its bioavailability is 100%

if the drug is given through oral route and all of it gets excreted into feces i.e. none of it gets absorbed into the blood then its bioavailability will be 0%

usually when a drug is given through oral route, much of it gets absorbed into the gut's blood supply which goes first into the liver (portal vein) and then into the systemic circulation. Liver acts as a first pass barrier, and metabolizes the drug so that some of it doesn't reach systemic circulation. For eg, if half of a drug that goes through liver gets metabolized to inactive compounds, then only half of the given dose will reach the systemic circulation. i.e. bioavailability is 50%

Efficacy is the "maximum" effect that a drug can produce, independent of dose think of it as a car that can go as fast as 150 km/hr, that's its max speed, once it is at that speed, no matter how hard you push the gas pedal, it won't go any faster. (that's the lame example i could come up with right now :p)

Potency is the amount of drug needed to have a desired effect Potency can best be explained by comparing two drugs.
using the same example from above, suppose car A and B both have a max speed of 150 km/hr. It means that they both have the same "efficacy". but lets assume that car A takes 20 seconds to get to the top speed, but car B takes 40 secs to get to that top speed. What this tells me is that car A reaches its efficacy in less time than car B does (still same efficacy). for pharma, car A is more potent.

meaning if Drug A and B both have the same desired effect, but drug A has that effect at a lesser dose than drug B, then A is more potent than B.

Hope this helps.
 
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