RE: Correcting for salt vs. base
Hi Dennis,
In my experience, most (but not all) doses are expressed as mg of free base,
eg, 0.5mg anagrelide (as 0.61mg of anagrelide*HCl). This facilitates changing
salt forms where the dose of free base may be unchanged while the dose of the
salt form will vary based on the size of the salt. I try to reinforce this
approach with my CMC colleagues whenever possible to ensure consistency.
However, I agree with you that calculation of clearance and volume should be
based on mg of the administered free-base in cases where the dose is expressed
as mg of the salt form.
Best regards,
Steve
Steven M. Troy
Clinical Pharmacology and Pharmacokinetics
Shire
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Wayne, PA 19087-5637
USA
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Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Fisher Dennis
Sent: Wednesday, March 26, 2014 8:57 AM
To: [email protected]
Subject: [NMusers] Correcting for salt vs. base
Colleagues
I have been troubled by a minor issue for some time. Consider the following
situation:
Dose is reported in mg salt
Cp is reported in ng/ml base
Since CL is dose / AUC and AUC is merely the integral of Cp vs. time, in
theory, dose should be converted to mg base (or concentration to ng/ml salt).
However, I am not sure if everyone does that.
In fact, an argument against it is that not doing the conversion permits one to
relate the administered dose (which is usually based on salt) to a Cp value
(usually based on base).
I am interested to hear what approach people use.
Dennis
Dennis Fisher MD
P < (The "P Less Than" Company)
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