Learnaboutgmp Community

MAC Calculations

Can someone help. If you calculate MAC, When do you use batch size in kg and when do you use no of units.


Dear Jay,

for the calculation of MAC, it does not matter if you take the batch size in kg or in units, as long as you keep unit consistency. Example, taking product A as the “contaminant” and B as the “contaminated” products, being a the active ingredient for A:

MAC= (Smallest therapeutic dosage of a)x(Batch size of B)x(safety factor)/(Largest daily intake of B)

Smallest therapeutic dosage of a: [mg a/day]
Batch size of B: [kg B/batch B] or [units B/batch B]
Safety factor: Usually 0,001, dimensionless.
Largest daily intake of B: [kg B/day] or [units B/day]

So the units are, in either case:

MAC=(mg a/day)x(units b/batch B)0,001/(units B/day)=0,001mg a/batchB

MAC=(mg a/day)x(kg B/batch B)0,001/(kg B/day)=0,001mg a/batchB

The key is to keep the batch size and the largest daily intake of B in consistent units (either in kg or in units), and to express the parts of the formula in the exact units, as not to confound [kg A] with [kg B]. Usually it is easier to calculate it in units because the largest daily intake is given in the product information in units/day.

Best regards


Thanks for the clarity.