In the 'PHARMACODYNAMICS

In the ‘PHARMACODYNAMICS : POTENCY, EFFICACY & DRC’ lecture, I have a query that -
During 23:02-23:17, you’ve mentioned that efficacy can be determined from a graded DRC using the curves’ height/slope. Sir, I understood the height part; however not the slope one.
As (in very basic mathematical terms) slope for any curve is the angle formed by the tangent drawn at a particular point & the X-axis. Also, the slope for any 2 parallel curves is same. So since Drug A & B have parallel DRCs (as proved later because they act on same target), they should have same efficacy as well (if slope is one of the determinants). However considering the height of DRCs, they are not having same efficacy.

The height of the curve says about the efficacy of the drug.

The slope of graph describes the pattern in which the response increases with regards to the dose. In a graph with steeper slope , a small increase in dose markedly increases the response.

Here the curves A and B are not parallel, if you observe carefully. The slope of B is more than that of A which means that for a small rise is dosage of grapB, the rise in the response is more as compared to that of drug A

The efficacy nevertheless, is described by the height of the graph

However, in the said lecture, the slopes of DRCs of Drugs A&B are same (as they’ve been informed to be parallel, due to their same target).

Withal, the slope of DRC of Drug C is lesser than that for Drugs A&B. So the fact said above, by you, would then suit accordingly.

Yes, technically efficacy is determined by height.

Slope tells us about the change in response per unit dose

So do the slope of DRCs eventually indicate the ‘SAFETY’ of drugs (as it’s a measure of change in response per unit dose)? Did I comprehend this right, sir?

As I’ve read it somewhere, who’s authenticity is not known. Hence, would like to get it confirmed from you, sir!

Not necessarily, bcs ultimately safety will depend on how wide the therapeutic window is.

Okay sir, sure. Totally understood.

Indeed grateful to you!