Patient Safety and Quality

Does anyone have any experience in using Rhophylac instead of Rhogam specifically the concern that if the BMI is > 30 IM Rhophylac may not be as effective as Rhogam when BMI > 30 ?? If you do would love to know how are you handling this are you doing IV for BMI > 30 ??

David McLean 

Hi David,

Where does this concern about Rhophylac dosing in obese patients come from?

The package insert does not mention obesity or BMI. 

This 2017 article concludes that obesity should not alter RhIG dosing

Considerations for dosing immunoglobulin in obese patients

If there is new info, please share the sources. 

Regards,

Andy Combs

Does anyone have any experience in using Rhophylac instead of Rhogam specifically the concern that if the BMI is > 30 IM Rhophylac may not be as effective as Rhogam when BMI > 30 ?? If you do would love to know how are you handling this are you doing IV for BMI > 30 ??

David McLean 

Andy

Thanks for the response in the product insert downloaded from the website : chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://labeling.cslbehring.com/PI/US/Rhophylac/EN/Rhophylac-Prescribing-Information.pdf

Hi David,

Where does this concern about Rhophylac dosing in obese patients come from?

The package insert does not mention obesity or BMI. 

This 2017 article concludes that obesity should not alter RhIG dosing

Considerations for dosing immunoglobulin in obese patients

If there is new info, please share the sources. 

Regards,

Andy Combs

Does anyone have any experience in using Rhophylac instead of Rhogam specifically the concern that if the BMI is > 30 IM Rhophylac may not be as effective as Rhogam when BMI > 30 ?? If you do would love to know how are you handling this are you doing IV for BMI > 30 ??

David McLean 

Oh, I missed that - I searched the Prescribing Information for "BMI" and "obes" so I did not find the "body mass index" mention.

This is anecdotal information - "there have been reports" .

How many reports, how big was BMI, what was time interval from event to dosing, what does "a lack of effect" mean?  Was this in pregnancy-related prophylaxis cases or ITP?

Theoretically, the concern about BMI and effectiveness would apply equally to Rhogam and Rhophylac.  The section on Post-Marketing surveillance starts with caveats about inability to determine frequency or causal relationship. 

The statement says "see Dosing and Administration (2.2)" but section 2.2 makes no mention of altering dose or route based on BMI.

The question is whether a change in practice is warranted by this information.  I suppose giving RhIg IV to obese persons would be a relatively benign modification. But without peer-reviewed evidence, it hardly rises to "standard of care" level.

Andy

Thanks for the response in the product insert downloaded from the website : chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://labeling.cslbehring.com/PI/US/Rhophylac/EN/Rhophylac-Prescribing-Information.pdf

Hi David,

Where does this concern about Rhophylac dosing in obese patients come from?

The package insert does not mention obesity or BMI. 

This 2017 article concludes that obesity should not alter RhIG dosing

Considerations for dosing immunoglobulin in obese patients

If there is new info, please share the sources. 

Regards,

Andy Combs

Does anyone have any experience in using Rhophylac instead of Rhogam specifically the concern that if the BMI is > 30 IM Rhophylac may not be as effective as Rhogam when BMI > 30 ?? If you do would love to know how are you handling this are you doing IV for BMI > 30 ??

David McLean