First thing, the spec of zero undercount is perfectly correct. We have IMA’s on our site, and the equipment spec is zero underfill. In terms of GMP, the filling operation may overfill but cannot underfill, as the equipment may be used for critical meds (patient-ready packs) where the patient cannot miss any doses. The overfill allowable is somewhere around 2 % on our site. Check the position of the bottles under the filling nozzle, make certain that no tabs are hitting the bottle or PI’s and bouncing out. Also confirm the accuracy of your counter by using specific amounts of tablets, as the problem often lies with the counter sensor settings being too sensitive and registering dust, etc, resulting in under counts. Repeat this exercise a number of times using a range of tablet size/type/bottle combinations. Dusty tablets are usually the worst-case products and a lot of attention needs to be paid to these, but highly polished dosage forms can also cause problems.
As a separate exercise, place specific amounts of tabs, enough to fill say 10 bottles, on the feeders from the filling hopper and use these to adjust the feeder vibration settings, etc until you get the correct fill amount with zero underfills. Then test under production conditions again. Ensure that the exercise covers a range of the products/containers intended for filling on the particular filling line. Once again, no undercounts should be allowed. Often a major problem is encountered with uncoated tablets which tend to leave dust on the counter sensors, causing an erratic beam which doesn’t always register when a tablet falls, or causes it to recognise more than one tablet. Problems also occur when packing small tablets at high feeder speeds where the tablets fall simultaneously, but their spatial alignment is such that the sensor only registers one tablet. Also, tablets which tend to stick tohether can cause count errors. These usually result in overfill errors.
Hope this helps…
