For curiosity I looked into weight gain via HU. This very old and small study for sickle cell looked into it. There should be larger studies I would think but interesting:
shows there is a connection, but not entirely a bad one.
<<At 18 months, the hydroxyurea-treated subjects exhibited an average weight gain of 3.16 kg. The mean weight gain in the placebo-treated subjects was 1.82 kg. Body composition analysis showed that the additional weight in both groups involved both lean and fat body mass components. In anaerobic performance, the subjects given hydroxyurea showed an increase in peak muscle power of 104.9 W. The placebo group also showed an increase, but theirs was a more modest gain of 57.7 W. The most marked improvement in anaerobic performance was observed in the hydroxyurea-treated men>>
<<The amount of Hydroxyurea that you will receive depends on many factors, including your height and weight, your general health or other health problem>>
I don't get the impression that our Drs consider our weight in dosing.
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EPguy
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That is correct. Weight is not considered in MPN dosing.
From ePocrates.com
Adult Dosing .
Dosage forms: CAP: 500 mg
Special Note
[uses, dosing may vary]
Info: refer to institution protocols and pkg insert prior to prescribing for uses, concomitant meds to mitigate toxicity, and dosing incl. toxicity-related dose adjustments; use lower of IBW or ABW for dose calculations
CML, refractory
[individualize dose PO qd]
Start: 15 mg/kg/dose PO qd
squamous cell head/neck CA, XRT adjunct
[500-1000 mg PO q12h x11 doses per cycle]
Start: approx. 14h prior to initiation of XRT each cycle
*sickle cell dz
[15-35 mg/kg/dose PO qd]
Start: 15 mg/kg/dose PO qd; Max: 35 mg/kg/day; Info: titrate by 5 mg/kg/day q12wk
*polycythemia vera
[500-1500 mg PO qd]
Info: titrate to control Hct and platelet count
*thrombocythemia, essential
[15 mg/kg/dose PO qd]
Info: titrate to control platelets and maintain WBC count
renal dosing
[adjust dose amount]
CrCl <60: decr. usual dose by 50%
HD: decr. usual dose by 50%, on dialysis days admin. after dialysis; no supplement; PD: decr. usual dose by 50%; no supplement
Interesting that most HU apps use weight. It could be that MPN presents a clear endpoint via the blood counts, and with such varied responses that is the better way to titrate the dosings.
Don't really know for sure, but a few other factors. HU is used in children with sickle cell disease. The purpose of HU in sickle cell is to alter the structure of the RBCs. Rather than reducing the number of blood cells, the goal is to change how they are shaped. As I understand it. where macrocytosis is a side effect for people with MPNs, it is the desired effect for sickle cell.
Macrocytosis is measured as MCV from what I see. That is also quantifiable, so there must be other reasons they use weight for sickle cell. Maybe HU in sickle cell has a more predictable effect. My initial HU does was too large, and I am a small guy, so that's why I've been curious.
Despite the dosing guidelines I certainly agree that weight matters. At a certain level that seems like common sense. There is also the more subtle differences in metabolism, Some people ar just more sensitive to drugs than others for a variety of reasons.
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