Dear Shyukh,
الجواب وبالله التوفيق
The rule regarding this issue according to the fuqahah is that things which the Islamic Shari‘ah have rendered impermissible, if their mahiyat is altered (i.e. through metamorphosis or complete change to their structure) as a result of a chemical change, then the rulings regarding their permissibility also changes. For example, in general, the mixture of water with grapes is permissible but when it becomes a completely different thing due to change in mahiyat i.e. sharab then it becomes najis. Similarly, when there is an utter change in the chemistry of sharab i.e. it becoming vinegar, then it becomes permissible for consumption.
(Mawlana Ashraf Ali Thanvi Sahib Rehmatullah Aleh) (Fatwah Zakariyah)
Therefore, as per the above rule, a halal animal which has been slaughtered in a non-Shar‘ai manner, due to a complete chemical change, if the mahiyat of its meat, blood, fat etc. has been changed, and has become something entirely new, then it is permissible for consumption.
Researcher, Ibn-e-Hāmhas documented in Fathul-Qadeer:
لان الشرع رتب وصف النجاسۃ علی تلک الحقیقۃ، و تنتفی الحقیقۃ بانتفاء بعض اجزاء مفھوما فکیف بالکل؟ فان الملح غیر العظم واللحم ، فاذا صار ملحاًترتب حکم الملح و نظیرہ فی الشرع النطفۃ نجسۃ و تصیر علقۃ وھی نجسۃ و تصیر مضغۃ فتطھر، والعصیر طاھر فیصیر خمرا فینجس فتصیر خِلا فیطھر الخ
(فتاوی دارالعلوم زکریا ص 601، ج10)
Mufti Taqi Usmani Sahib states:
الخمائر والجلاتین المتخذۃ من الخنزیر ان کان العنصرالمستخلص من الخنزیر تستحیل ماھیۃ بعملۃ کیمیاویۃ بحیث تنقلب حقیقۃ تماما زلت حرمتہ ونجاستہ ان لم تنقلب حقیقہ بقی علی حرمتہ ونجاستہ لان الانقلاب الحقیقۃ موثر فی زوال الطھارۃ والحرمۃ عندالحقیقۃ
(فتاوی دارالعلوم زکریا ، ص 603، ج10 بحوالہ بحوث فی قضایا فقھیۃ معاصرۃ)
The external use of alcohol extracted from things other than grapes, raisin and dates is permissible. However, according to the ruling of Hazrāt-e-Shaikhain, its usage in medicine is only permissible in situations of extreme and dire need and due to its prevalent and common use.
(Same reference as above)
واللہ اعلم بالصواب