Anybody having an experience with the response of FDA regarding cutting/overwriting in the weights or dilutions while writing in the laboratory notebook.Is approval/authentication of the cutting by Head of Department is acceptable or not?

I am not sure what you mean by cutting. In terms of overwriting, you may never do this. The data needs to be completely legible. You may cross out with a single line, initial, date and give reason for correction. In terms of GLP (not necessary gmp) you can change the weights used (is this what you mean by cutting), but the study director must issue a protocol deviation, sign it and have the sponsor of the study sign it. This will remain with the original copy of the protocol in the study file.