Suspensions terminal sterilization

Injections may be aqueous solutions, oily solutions (because of poor aqueous solubility or the necessity for a prolongation of drug activity), aqueous suspensions or oily suspensions. They may be asepti-cally produced or terminally sterilized in their final containers. Those drugs that are unstable in solution may be presented as a freeze-dried (lyophilized) powder. The choice of final packaging should not determine the method of sterilization. 

Table 1 lists some examples of sterile parenteral products classified as LVPs or SVPs, as a.septically filled or terminally sterilized, and as solutions, suspensions, or solid dosage forms. 

Products such as suspensions, ointments and creams which are to be terminally sterilized should also be prepared under Grade 2 conditions. 

The liquid formulation for parenteral administration requires additional physical and microbiological functionalities, such as syringeability, sterility, osmolarity, and pyrogen freedom. The particle size change can influence the syringeability of injection of a suspension formulation as well as the level of irritation at the site. Terminal sterilization such as autoclave or gamma irradiation may affect the physical stability of the dosage form. Both formulation and container systems should be evaluated [63]. 

Wong J, Papadopoulos P, Rebbeck C, Schwabe S, Lischewski G, Melchert J, Kuu W, Agostinelli T, Smith T, Brame G, Lynn R, Hepler D (2004) Effect of terminal sterilization by irradiation on amber Type I and Type III glass containers containing veterinary oxytetracycline suspension. PDA J Pharm Sci Technol 58 6-14. 

If the suspension is for parenteral administration, it will need to be sterilized. Terminal heat sterilization can affect both its chemical and physical stability, the latter usually observed as crystal growth or aggregation of the particles (Na et al. 1999). Another measure of suspension stability is the zeta potential, which is a measure of the surface charge. However, various... 

Like suspensions, ointments can be more difficult to manufacture in sterile form. They can be terminally sterilised alternatively, they must be manufactured from sterile ingredients in an aseptic environment. Filtration through a suitable membrane or dry heat sterilisation is often used. 

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