WEIGHT BASED DOSING QUESTION

[earthwarrior54]

Hi I am curious if anyone has found a chart or info on how much interferon, ribavirin and telaprevir a person should take based on their weight. Maybe some of these are not even weight based altho it sure seems like a 100# person would not require as much of any of these as a 300# person but I don't know. If anyone has a link to this or a chart or any info, I'm just curious to know. Thankx

[lynda607]

In the Telaprevir (Incivek) trials the ribavirin dosage was either 1000 mg or 1200 mg daily.  I don't know the conversion chart they used but I would think 65 kg or below 1000 mg.  Above 65 kg 1200 mg.  According to HGB level drops, ribavrin dose reduction was given if necessary.  

Telaprevir trials used Pegasys (peginterferon alfa-2a) 180 mcg universally.  Pegasys is not given as an individualized weight-based dosing like PegIntron (peginterferon alfa-2b)

Incivek is administered two tablets 375 mg ea - 3 times a day every seven to nine hours universally.  

[pooh55811]

Here is the link to an article about weight based Ribavirin dosage:

http://hepatitiscnewdrugs.blogspot.com/2011/05/optimal-dose-of-ribavirin-for-chronic.html

And here is a portion of that article:

A relationship between RBV dose and response to therapy with both IFN alpha-2a and alpha-2b has been established in genotype 1 patients, who benefit from doses that exceed 800 mg/day (5, 14). When RBV is combined with PEG-IFN alpha-2a, relatively small reductions to 800 mg/day lead to significantly lower rates of SVR (5). Similarly, a large comparative trial of fixed-dose RBV compared with weight-based dosing in combination with PEG-IFN alpha-2b demonstrated that stratifying patients of all genotypes to receive starting doses ranging from 800-1400 mg/day depending on weight effects higher SVR rates than using a fixed dose of 800 mg/day for all patients (7). A detailed analysis of the relationship between body weight and SVR has suggested that the dose per kilogram is the determining factor of response in genotype 1 patients, based on the 40% to 50% rise in SVR for a 12-16-mg/kg increase in RBV dose (23). RBV dose by weight may impact its concentration in plasma, which also correlates with the response. Although this relationship has been well documented in genotype 1 patients, the data are less clear for other genotypes. A relationship between response and plasma concentration has been proposed for non-genotype 1 patients (24). However Snoeck et al. observed no effect of dose per kilogram body weight on SVR in genotype 2/3 patients (23).
Based on these data, weight-based dosing has been used more extensively in patients with genotype 1 HCV, and it is required to achieve maximum efficacy. The standard initial dose of RBV in patients with HCV genotype 1 is 1000/1200 mg/day (1000 mg/day ≤ 75 kg; 1200 mg/day > 75 kg) over a 48 weeks, although higher RBV doses are considered for patients > 85 kg. A study of 380 patients has shown that the pharmacokinetics of RBV vary widely, wherein lean body weight emerges as the only factor that influences clearance, supporting the use of these two distinct weight-based doses in patients with genotype 1 disease (25). Although data modeling from patients who received this standard starting dose suggests that SVR increases linearly with RBV doses that equate to > 10 mg/kg, the rate of anemia also rises linearly simultaneously (< 10 g/dL hemoglobin) (23). An RBV dose of 15 mg/kg/day might achieve the best balance between efficacy and a manageable safety profile.

[brianmo]

I recently asked this same question so if you go to my profile you can see past responses. As far as I know, it's the Ribavirin that is weight based. I am 114 and they have me on 1000 mg a day. This is right, the high end. I feel fine, no sides as a yet.