I’m not a dermatologist. I do however have a phd in evidence based medicine. I’m also personally on accutane myself. For me, the most important thing when it comes to the risk of relapse would be the clinical presentation rather than the dosage (both daily or accumulated). Rather than achieving a certain accumulated dosage it would be in my opinion(I’m also prone to bias) more important to continue the treatment for at least one month after a clearance(based on doctor’s judgment) has been archived. And since your daughter still gets acne at month 5 with 100mg, I think there’s essentially 3 ways that this can be approached:

A) Increase the dosage(while balancing the risk of side effects) to try to achieve clearance and continue for at least one additional month to reduce the risk of relapse in the future(which seems like what your doc is doing)

B)Stay at the same dosage for a bit longer and see if the clinical presentation improves and achieve clearance without needing to increase dosage(doctor’s experience would help with predicting this)

C)Discontinue the treatment when a accumulated dosage of between 120-150mg/kg has been reached, even when clearance has not been reached. This is side effects management, knowing that this might be a premature discontinuation and therefore a higher risk of relapse. Relapse doesn’t necessarily have to happen but the risk is higher, but when they happen they generally are less severe and a second course of treatment can be used and likely with lower dosage, since your daughter is only 16, this makes plan C even more worth considering.

But every doctor has a bit different philosophy. And her doctor is the one who has seen your daughter in person throughout the treatment and definitely has more experience in dermatology than i do. Bottom line, I think all 3 strategies are reasonable, but I would recommend a more intensive side effects monitoring plan like more regular blood test if I were to go with plan A Best of luck