فارما..

السلام عليكم... بعض النقاط اللي في الجزء بتاعي كتبت الاشياء المهمة باختصار بتساعد في الفهم اكثر من التلخيص... اتمنى تفيدكم

Affinity :


- Is the ability of drug to combine with the receptor.
- Drug + receptor  drug receptor complex  effect.

Efficacy :(intrinsic activity)

increase concentration  increased efficacy
- Is the capacity of drug receptor complex to produce an action.
- Is the maximal response produced by a drug (Emax).
-
- It depends on the number of drug-receptor complexes formed and the efficiency with which the activated receptor produces cellular action.

» E.g. if a Drug A can reduce the blood pressure from 160 to 140 in dose of 10 mg. and Drug B reduces the pressure of 160 to 150 in a dose of 5 mg.
▪ Drug A is therefore has more efficacy than does Drug B

Note, even if we increase the dose of Drug B upto 10 mg it will not reduce the blood pressure to less than 150 but it will have adverse effects.


Dose-Response Curve :
- Graded dose-response curve. E.g. Ach.
- Quantal (all or none) curve to measure the degree of toxicity.

Median Effective Dose ( ED50) : -
- It is a dose of the drug that gives 50% of the maximal response.
- Is a measure of the potency.

Potency :
▫ it is inversely proportional to ED50
▫ it is a measure (in weight) of how much ( amount) drug is required to elicit a given response ( produce action ).
▫ It depends in part on the affinity of receptor for binding with drug and in part on the efficiency with which drug- receptor interaction is coupled to response.
▫ The lower the dose required for given response ,the more potent is the drug
▫ it is most often expressed as the dose of drug that gives 50% of the maximal response
▫ How ever efficacy is more important than potency clinically.

Difference between efficacy and potency:

►Amiloride(low efficacy) can cause no more
than 5% of
filtered sodium to be excerted

►Benzofluride ( moderate efficacy) cause
about 10 % excretion of filtered sodium

►Frusamide ( high efficacy ) cause 25%
excretion of filtered sodium.

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