Manual Visual Inspection is an important step in pharmaceutical manufacturing which aids in the detection of various formulation defects. The defects are observed in the all types of formulations viz. tablets, capsules, injectables etc. To effectively observe the defects there are many requirements w.r.t. trained and qualified operators, Inspection belt, lighting, background etc.

In this series on pharmaceutical product inspection, we shall be discussing various aspects of manual visual inspection serially. Previously, we had already discussed about the “Lighting requirements for Manual Visual Inspection of Pharmaceuticals”.

Accordingly, this article shall provide information on the rate of inspection i.e. minimum time required to inspect the product.

Inspection rate: During inspection of drug products to identify any defect or contamination, a question normally arises as for how much time a container/ unit should be inspected. Although, it is a subjective question and the rate of inspection depends on inspector’s training and capabilities and on the nature of the packing material and the product itself. However, as per the requirement sufficient time must be provided for the thorough inspection of each container. USP, IP and various other International Pharmacopoeias specifies a reference time of 10 s/container (5 s each against both black and white backgrounds).

Larger or more complex containers may require additional time for inspecting all attributes. Increased time may facilitate detection of defects near the threshold of detection, but studies suggest that there are diminishing gains with increasing inspection time. Time spent per container may be controlled through extensive training. The time spent for inspecting each batch shall be recorded. This shall further aid in calculating the nominal inspection rate to confirm that the rate of inspection was within established limits.

Importance of Contrast: The contrast between the defect of interest and the surrounding background is required for detection, and increased contrast improves detection. The apparatus consists of a viewing station comprising of a matt black panel of appropriate size held in a vertical position and a non-glare white panel of appropriate size held in a vertical position next to the black panel. The use of both backgrounds provides good contrast for a wide range of particulate and container defects, which can be light or dark in appearance.