charcot_bouchard2nd update : cont to learn school grade chem. if pKa > 7 it is base. and if pKa is < 7 it is acid. Since we established the drug have to be a weak acid pKa cant be more than 7. +2019-07-13T10:17:30Z
dbgthanks, but Pka and PH are not at all the same thing+2019-07-19T02:16:01Z
kingtime9119But that doesn't make sense. Page 233 of First Aid 2019 edition clearly states that being plasma protein bound creates the lowest volume of distribution, because not being bound to proteins increases the chance it will reach deep into the tissues before it reaches the kidneys. Discrepancy with First Aid?+2019-05-16T22:17:30Z
haliburtonmy reasoning was comparing two drugs, both with Vd of 1, the drug with the lower albumin binding would be cleared faster @kingtime. I don't think you're considering that A and B have equal Vd.+12019-05-16T22:22:37Z
masonkingcobraSince an ionized form is charged (by definition), it will not easily cross a nonpolar lipid membrane. Thus, it is important to recognize the potential of the drug to ionize in order to predict its solubility and the degree to which it can be reabsorbed. The degree of ionization is determined by the drug’s pKa and the pH of its environment. Weak acids and bases are 50% ionized and 50% unionized when the surrounding pH equals the drug’s pKa. At 2 pH units above or below the pKa of the drug, nearly 100% of the drug is ionized or unionized.+22019-05-24T04:39:52Z
masonkingcobraBasically weak acids are best excreted in alkaline urine, but weak bases are excreted more readily in acid urine. +2019-05-24T04:45:07Z
masonkingcobraIn summary, because this is a weak acid at pKa 6, making the urine alkaline will result it its ionization and excretion. Ionized cant move through lipid membranes so can't get reabsorbed and is pissed out. +12019-05-24T04:47:34Z
yexFollowing on masonkingcobra explanation:
A pKa 4-9 can be either weak acid or base.
Weak acid pKa 4-7; strong acid pKa 1-3
Weak base pKa 7-9; strong base pKa above 9
Differents pHs: stomach: 1-2 duodenum: 3-5 early jejunum: 5-7
late jejunum: 7-9 ileum: >9 urine: 4.5-8
Weak acids (pKa) gets absorbed in acidic (pH) environments and cleared in basic. Weak bases gets absorbed in basic environments and cleared in acidic. THIS DOES NOT APPLY TO STRONG BASES OR ACIDS!!!!
The best explanation for this is a Biochem lecture from Pass Program and it is available on YouTube, its long but it is for sure worth it!! Look for 19 Biochemistry 1 from Pass Program on YouTube. +12019-07-03T16:59:39Z
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