What is the relation between Chemical Engineering and Pharmaceutical?

Pharmaceutical require GMP (Good Manufacturing Process) based on chemical engineering unit operation.
Pharmaceutical require basic and fundamental formulation and analysis while chemical engineering determine cost effective process based on feasibility study.
Chemical Engineering is used for the mass production of pharmaceutical products or life saving products.
Chemical Engineering could be applied as per scenario; food, chemical, petrochemical, polymer, bio chemical, minerals, herbal etc, while pharmaceutical is specific area of chemical engineering.

The pharmaceutical industry relies heavily on purity, quality control, and chemical and biological reactions.
For this reason, it is important to understand how to increase the purity of a compound, control its variations, and produce it in an economical fashion.
For example, using Continuous Stirred Tank Reactorss in series in a reaction A->B->C->D is a much better way to control for B & C than using a single CSTR.
You must also understand how shifting the pH or temperature will have an effect on the downstream product.