Pharmacology in Nursing Practice

2 responses so far ↓

• 1 Jenny Brown // May 31, 2008 at 7:33 am

  I have a question about potency. I understand the definition; The dose it takes to get a response, however, I am confused about the statements in the module concerning morphine vs. demerol. It says that morphine and demerol both have equal efficacy but you should use morphine b/c it has less milligrams and thus potentially less side effects. When I sold Allegra (a long time ago..:) ) there was never a question of potency or side effects when selling compared to Claritin. Allegra’s QD dose is 180mg and Claritin’s QD dose is 10mg. The side effect profiles were the same. Is that different for other drug classes? I thought the mg difference had to do with molecular structure. ??

• 2 Mrs. Thames // Jun 2, 2008 at 12:19 pm

  Good question: the mg or mcg difference has to do with potency of the drug, when you compare it to another drug in the class. So, for Allegra, which requires 180 mg, it is less potent than Claritin. This does not mean that Allegra is less efficacious, just that it requires a higher dose than Claritin to achieve the same effect.

  Usually, as a dose increases, so do side effects. We don’t always want the most potent drug - it depends on the patient.

  Morphine is preferred over Demerol for other reasons than potency, which you will learn in the pain module; however, as far as potency goes, morphine is a higher potency drug than meperidine.

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