Rheological characteristics of products

The rheological behaviour of liquids and semisolids can be described as discussed in sections 7.3.10 and 7.4.4 of Chapter 7. Viscosity monitoring can be used as a quality control procedure, but some very practical rheological tests may be carried out. Some are discussed here. 

The injectahility of nonaqueous injections, which are often viscous and thus difficult to inject, can be assessed by a test for syringeabil-ity. Sesame oil has a viscosity of 56 cP, but added dmgs and adjuvants can increase the viscosity of such vehicles. 

2 Other commonly used ointments Soft and unctuous, but stiff enough to remain in place when applied  

3 Protective ointments, e.g. zinc oxide paste Hard and stiff remain in place ulcerated areas when applied to moist 

Visual appearance (e.g. paste, liniment, cream, etc.) Sampling characteristics Ease of removal from container (e.g. extrudobility, if in tube) 

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