Choose the true statement(s) about therapeutic index (TI). Sel...

Question

Choose the true statement(s) about therapeutic index (TI). Select all that apply. (NCLEX/HESI/TEAS)

a. A drug with a high therapeutic index would be effective above the dose at which it is potentially toxic.

b. A narrow TI is preferable.

c. A drug for which the maximum safe dose is close to the minimum effective dose would have a high TI.

d. It is one measure of a drug’s general safety.

e. A drug that is not selectively toxic would most likely have a high TI.

Accepted Answer

Hi, everybody. Welcome back. Our next question says which of the following statements about therapeutic index or T I is false. A? It is the ratio of the minimum effective dose to the maximum safe dose B. It refers to the measurement of drug safety C A higher T I means the drug is safer D drugs with lower T I mean regular monitoring or E none of the above. And it can be a little tricky with a question formatted like this when it's asking for a false statement. And then we have none of the above that would mean that all statements are true. So just kind of keep that straight as that can be a little confusing. So let's work our way through each of these statements and determine which one is the false one if there is one that's false. So first of all, we have one about the definition of therapeutic index. So choice says it's the ratio of the minimum effective dose to the maximum safe dose. Well, this right away is a false statement because this is reversed. The actual formula for therapeutic index or T I equals the maximum safe dose or rather the maximum safe or tolerated dose. A dose might be safe as in not actually causing harm, but maybe is too harsh or has side effects that can't be tolerated. And that's in the numerator divided by the minimum effective dose or you might say minimum therapeutic dose. So choice A is false because it has those two reversed. So we already have our false statements and we know that choice E none of the above is not our answer. But let's just look at our other answer. Choices to be thorough. B it refers, refers to the measurement of drug safety. Well, this is a true statement because it relates how much you need to have a therapeutic effect to how much can actually be tolerated safely. So is, can you tolerate a large enough amount to have the therapeutic effects? So that's not the answer. Since it's true. Choice C says a higher T I means the drug is safer and indeed drugs with lower T I need regular monitoring. But wherever we have ratios, sometimes we have to think a little closely about what they mean exactly. So since our numerator is the maximum safe dose, the higher the numerator, so we'll put a little up arrow. So higher the numerator, the um safer the drug because you can have a s take a larger amount safely and then the lower the denominator minimum effective dose, the safer the drug because it means you don't have to take much to get the benefit of the drug. So you don't have to um, worry about so much about taking too much. So this drug will be safer in general. The higher this number is because a higher numerator will obviously make a larger number and a smaller denominator makes a larger number. So both of those work together, not against each other. So choice C, a higher T I makes, it means the drug is safer. That's true. So not our answer. And in choice D drugs with lower T I need regular monitoring. And this is also true because it means that the dose you need to take to get the beneficial effect is closer to the level at which the drug is no longer safe. So you would want to monitor patients taking those doses to make sure you're not starting to see harm happening to their body as a result. So that's why choice D isn't our answer. So once again, the statement about the therapeutic index or T I that is false is choice A, it is the ratio of the minimum effective dose to the maximum safe dose because this is exactly reversed. See you in the next video.

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