You need following to become drug inspector in India.

• Minimum bachlor’s degree in pharmacy medicine or microbiology.
• Minimum 18 months experience in manufacturing or analysis of schedule C drugs (antibiotics or parenteral products).

This is the common criteria for drug inspector post few minor variations are there statewise

You can get good imformation about this in following link Eligibility And Qualification For Drug Inspector In India - Pharmagang

Hope this will help