Baruch:
If I understand your first situation, you should have a
residue limit for AAA and for BBB in CCC. These limits can be
calculated independently of the equipment used. The next step
is to calculate the limit per surface area based only on those
pieces of equipment that can contribute to the residue. The
limit for AAA per surface area of equipment a,b,c is based on
the limit of AAA in CCC, the batch size, and the equipment
surface area. The limit for BBB per surface area of equipment
e,f,g is based on the limit of BBB in CCC, the batch size, and
the equipment surface area. Lots of people use a MAC
calculation. However, I like to use an approach that I
presented in a paper published in Pharm Tech in October 1998
(it was also published in Pharm Tech Europe in the spring of
1999), that separates out the limit in the next product, the
limit per surface area, and the limit per analytical sample.
Mike Mullen, who co-authored the orginal Lilly article on
limits, also likes my approach. You might want to review my
article. If I'm correct on the analysis of your first
situation, the "another approach" becomes moot.
Note that this calculation of limits of both AAA in CCC and
BBB in CCC assumes that there are special issues
(interactions??) with the presence of both these residues in
CCC.
Destin LeBlanc
STERIS Corporation
destin_leblanc@steris.com
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