PROCESS DESIGN OF TOPICAL SEMISOLIDS

This chapter focuses on the unique considerations and challenges associated with the clinical and commercial-scale manufacture of topical semisolids. In particular, it focuses on one subset of topical ointments, polyethylene glycol (PEG)-based ointments. The chapter describes the considerations involved in formulating a PEG ointment – in particular the advantages and disadvantages from skin delivery, solubility, and stability perspective. Once the composition of the formulation is finalized, one now needs to devise a process to manufacture the ointment. The chapter discusses an example of how the manufacture of an ointment goes from a benchtop lab scale (~100 g) to the commercial scale (~1000 kg). Manufacture of the PEG ointment described in this chapter requires a vessel capable of mixing the material and maintaining a consistent temperature as the product cools and congeals. The chapter shows a general process flow diagram for the PEG ointment. It discusses the dissolution and congealing/annealing steps in greater detail.