Q:

6/16/2014
I would like to obtain any new update or guidelines in regarding IVIG dosing based on actual BW to an ideal body weight (IBW). Given that IVIG has a low volume of distribution and does not distribute highly throughout tissues, alternative dosing based on IBW has been recommended at other institutions and European guidelines. Studies reviewing outcomes have shown clinically no differences between using an IBW, adjusted BW or actual BW. Some data even demonstrates the cost savings when an IBW was used in place of actual BW. Dose in mg/kg/dose remained the same.

A:

Thank you for your inquiry.

Your question is similar to an inquiry to which we responded a couple of years ago. For your convenience, I have copied below this question and the response from Dr. Mark Ballow. In essence, to my knowledge, there has been no change in the status of the discussion as to whether or not to dose by ideal weight or real weight. But, I am going to expand our answer in hopes that the additional information will be of help to you.

There has been an argument to dose by ideal body weight (see Seigel reference copied below). However, as you can see from the article by Khan, et al. (abstracted below), as Dr. Ballow mentioned, dosing by clinical outcome at this time appears to be the most appropriate strategy to follow, and the results based on ideal versus real body weight do not allow for a definitive opinion at this time.

There is an excellent in-depth discussion of this issue in an article from the University of Illinois, College of Pharmacy. A link to this article is copied for you below for your convenience.

It is important to note, as discussed in this article, that Guidelines from the United Kingdom published in 2007 recommended replacement therapy be based on adjusted body weight. However, these recommendations were eliminated from both the 2008 and 2011 updates because evidence to support this practice was too limited to make a firm recommendation.

Thank you again for your inquiry and we hope this response is helpful to you.

Administration of intravenous immunoglobulin based on actual versus ideal body weight
Question:
12/13/2012
Does the AAAAI have any guidelines or position on dosing IVIG on actual vs ideal body weight? Based on the pharmacokinetic profile and distribution characteristics, dosing with ideal body seems to make sense, and many institutions around the country do this. I would be very interested in an opinion. Thanks very much.

Response from Dr. Lieberman:
The AAAAI does not have a position regarding your question, but I am sending your inquiry to Dr. Mark Ballow, who is a nationally known expert in treatment of immunodeficiency disorders including the administration of immunoglobulin replacement therapy. As soon as we hear from Dr. Ballow, we will forward his response to you.

Thank you again for your inquiry.

We have received a response from Dr. Mark Ballow regarding your Ask the Expert question. Thank you again for your inquiry and we hope this response is helpful to you.

Sincerely,
Phil Lieberman, M.D.

Response from Dr. Mark Ballow:
I am not aware of any recommendations for IVIG dosing for ideal vs actual weight. The more important variable is the clinical response. It is reasonable to start with ideal weight but the dose may have to be adjusted to control infections - the biologic trough level. A paper by Berger et al (Clin Immunology 139:133, 2011) reported bioavailability of SCIg and showed that obese individuals had bioavailability correction factors higher than individuals with normal BMI. However, he concluded that the mean dose adjustment should only be rough guides and each patient's optimal IgG level and dose should be determined individually by their clinical response. Another article (editorial) that might be of interest is that by Bonilla (Clin Immunology 2011).

Mark Ballow

Drug Metab Lett. 2011 Apr;5(2):132-6.
Serum trough IgG level and annual intravenous immunoglobulin dose are not related to body size in patients on regular replacement therapy.
Khan S1, Grimbacher B, Boecking C, Chee R, Allgar V, Holding S, Wong G, Huissoon A, Herriot R, Doré P, Sewell W.
Author information
1Department of Immunology, Frimley Park Hospital NHS Foundation Trust, Portsmouth Road, Frimley, Surrey, GU16 7UJ, United Kingdom.
Abstract
Therapeutic regimens of intravenous immunoglobulin are currently based on actual body weight. The relationship between immunoglobulin dose and serum IgG level in relation to body size was retrospectively explored in patients on replacement therapy. Data were collected as part of a national audit on immunoglobulin therapy in patients with common variable immunodeficiency. 107 patients received immunoglobulin titrated to optimum effect. Correlations were sought between body mass index, trough IgG levels, infusion frequency and total annual dose. The mean (±SD) trough IgG level was 8.4±1.6 g/L and annual immunoglobulin dose received was 456.8±129.4 g. There was no relationship between annual dose and trough IgG level, regardless of infusion frequency, or adjustment for weight or body mass index. These results support the clinical practice of immunoglobulin prescription by clinical outcome rather than fixed dose by body weight. Future studies exploring immunoglobulin efficacy should include treatment arms with dosages based on both ideal and actual body weight, as ideal body weight-based prescribing would save significant amounts of product.

University of Illinois College of Pharmacy

Reference:
Seigel, J. Immunoglobulins and Obesity. Pharmacy Practice News, 2010; 37(1).

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology