## identical pH [Dissolution / BCS / IVIVC]

Hi amer,

» I have constructed IVIVC using in vivo data and dissolution data done at pH 1.2. if i have a new dissolution data (say done at pH 2), how can i predict the in vivo concentrations based on the new dissolution…

Dissolution at $$\small{pH\;2}$$ is rather unusual. Recall the definition: $$\small{pH=-\log_{10}[\text{H}^{+}]}$$, where $$\small{[\text{H}^{+}]}$$ is the activity of the $$\small{[\text{H}^{+}]}$$ ion. Hence, at $$\small{pH\;2}$$ you have $$\small{10^{0.8}\approx6.31\times}$$ lower activity of $$\small{[\text{H}^{+}]}$$ than at $$\small{pH\;1.2}$$. Whether this is relevant, depends on the $$\small{pk_\text{a}}$$ of the drug. However, it might lead to wrong conclusions.

Valid predictions based on IVIVC require dissolution at identical pH values. Repeat the exercise at $$\small{pH\;1.2}$$.

Dif-tor heh smusma 🖖
Helmut Schütz

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