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Risherd ☆ Mexico, 2010-04-09 00:26 (5926 d 14:09 ago) Posting: # 5056 Views: 3,178 |
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Let's suppose that we are doing a bioequivalence study of a drug which binds 75% to plasma proteins and 98% to erythrocyte carbonic anhydrase. Also, the drug is excreted unchanged at 70% in urine. Do i have to use plasma, whole blood or urine, which one of them should we use? If we use plasma we are not going to quantify the drug's total concentration in the systemic circulation; If we use whole blood, we are going to have additional problems extracting the drug from the biological matrix because of the Red Blood Cell's haemolysis, but we're going to quantify the total amount of the drug at the given time; If we use urine, the extraction of the drug from the biological matrix will be easier, but we are not going to quantify the total amount only the 70%, and we will be adding logistic problems to the clinical unit. Which matrix will be the best choice? I hope you can tell me some advices for this situation. Best Regards, Ricardo. |
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Helmut ★★★   Vienna, Austria, 2010-04-09 04:50 (5926 d 09:45 ago) @ Risherd Posting: # 5058 Views: 2,559 |
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¡Hola Ricardo! ❝ […] a drug which binds 75% to plasma proteins and 98% to erythrocyte carbonic anhydrase, […] excreted unchanged at 70% in urine. Let’s call the drug chlorthalidone.  ❝ Do i have to use plasma, whole blood or urine […]? If my guess is right – whole blood. Sorry, one of the rare exceptions. Yes, I know, it’s a mess, but check the literature yourself. Hints for analytical method development: 1 mL thawed whole blood + 3 mL H20, centrifuge at 2000×g at +4 ℃ for 20 minutes, C18 SPE… It should be possible to get inaccuarcy ~±5% at a precision of ~5%, no problems with freeze-thaw-cycles, and storage at -20 ℃ for at least three months. Don’t worry about a recovery of ~70%. Good luck! — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
Ing. Helmut Schütz