Step I pharmacokinetic q

[mjl1717]

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What Percent of "Durabine" a weak organic base, would at equilibrium be expected to be absorbed from the intestines under the following conditions. pk of Durabine =7.4; pH of intestine =9.4; pH of blood = 7.4?

a)94%
b)67%
c)34%
d)0.01%
e)10%


Can someone answer this without using the Henderson Hasselbach equaiton?

 

[mjl1717]

Are their any brave pharm majors out there to attempt this q?

 

[hale-bopp]

Are their any brave pharm majors out there to attempt this q?

why do you need to answer it without H-H?

 

[Idiopathic]

What Percent of "Durabine" a weak organic base, would at equilibrium be expected to be absorbed from the intestines under the following conditions. pk of Durabine =7.4; pH of intestine =9.4; pH of blood = 7.4?

a)94%
b)67%
c)34%
d)0.01%
e)10%


Can someone answer this without using the Henderson Hasselbach equaiton?

Its been so long...weak organic base in a basic environment, so ~1% will be ionized, right? This leaves lots of unionized and lipid soluble durabine in the gut, so I would think the answer would be a. i guess technically the H-H equation is used, but not explicitly.

 

[felipe5]

hmmm, i thought about this one for a while.....is the answer B? in the intestine the ratio of unionized to ionized would be 100:1.......the unionized form would then be free to travel to the bloodstream and it would equilibrate in the blood with the same concentration there (say 100)...in the blood, ionized:unionized should be 100:100....compare the blood:intestine concentrations and you'll see that the blood:intestine ratio of the entire drug should be 200:101, or about 2:1....meaning that 2/3rds of the drug was absorbed??? who knows i could be hella wrong 🙁

 

[Idiopathic]

hmmm, i thought about this one for a while.....is the answer B? in the intestine the ratio of unionized to ionized would be 100:1.......the unionized form would then be free to travel to the bloodstream and it would equilibrate in the blood with the same concentration there (say 100)...in the blood, ionized:unionized should be 100:100....compare the blood:intestine concentrations and you'll see that the blood:intestine ratio of the entire drug should be 200:101, or about 2:1....meaning that 2/3rds of the drug was absorbed??? who knows i could be hella wrong 🙁

That sounds better. I had it right until it got to the blood

 

[mjl1717]

why do you need to answer it without H-H?

Because Dr. Goljan and others are saying its too inverted & misleading.
Although its still taught at some schools.

 

[mjl1717]

Its been so long...weak organic base in a basic environment, so ~1% will be ionized, right? This leaves lots of unionized and lipid soluble durabine in the gut, so I would think the answer would be a. i guess technically the H-H equation is used, but not explicitly.

Idio & Felipe, I dont know the answer, saw this on the other forum. As always thx for the help. [by the way that's quite an avatar, Idio.]