My dad was told his dose of gabapentin is going to be increased to 2100mgs/dayhe suffered nerve damage in his face but is this much medication harmful?

No: Officially, this medication can be used – for other purposes – up to 3600 mg per day. Start slow. Increased slow. Do not discontinue abruptly – might potentially cause seizures if stopped abruptly. Otherwise, they are safe and effective medication. Good luck

Neurontin (gabapentin): 2,100 mg. Neurontin, (gabapentin) probably dosed at divided doses 3 times daily, is not maximum daily dose. Review with his doctor if any adverse effects occur.