Calculation of the Maximum Daily Dose (MDD) in Mouthwash Products

Limits of Nitrosamines
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Hello everyone,

I am trying to calculate the Maximum Daily Dose (MDD) for a mouthwash product.

For example, if a patient uses 15 mL of mouthwash three times daily, and each 15 mL dose contains 22.5 mg of the active pharmaceutical ingredient (API), what value should be considered as the MDD?

My specific question is whether the MDD can be considered lower because the patient is expected to rinse and then spit out the mouthwash, thereby ingesting only a fraction of the API. Should the MDD be based on the theoretical worst-case scenario and therefore be considered as 67.5 mg/day?

I would appreciate your guidance on the appropriate regulatory/scientific approach.

Thank you in advance.

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I would approach the risk analysis exactly the way you propose, assuming the MDD as 67.5 mg/day. This is in line with the statement in the Q&A (“The same risk approach is applicable to all routes of administration. Corrections to limits are generally not acceptable.”).

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I think it is appropriate to consider only the fraction ingested - the majority is spit out, so does not represent an exposure.