Pharmacy Courses

Black Spots or Specks on Uncoated Tablets

Very recently one of my favorite friend and pharmaceutical scientist brought to my attention about his encounter of getting black specks on the uncoated white tables during compression and jotted down the following possible causes - 

1. Raw material 

2. Oil setting for the punch lubrication 

3. Flying  dust rubbing on exposed upper punch body and dropping inside die during turret rotation 

4. Scrapper collections of Very fine cohesive powders 

He wanted to discuss this matter and get my professional opinion. We were discussing this undesired situation and what could be the other possible reasons. During our discussions I suggested  the following fish bone phenomena type of checking should be performed to find out the root cause besides the above mentioned factors. 

If this problem is first time encountered for a new product then to check the pH of the substrate for compression. Sometimes if the compression substrate is acidic and sitting for a long time in the tablet press, it may have a reaction with the metal parts of the turret and the feed frame, as these parts are not made of S.S rather the scrapping blades are made with brass which is nickel-copper alloy and usually soft.

To check the above stated feed-frame and it's scrapping blade are they worn-out?

Too much tightening of these assembly on table of the tablet press may cause scrapping of the metal.

Similarly putting feed-frame assembly Very close to the rotating turrets may also cause scrapping.

These issues have to be resolved independently and if needed on  placebo batches. 

Hope we have been able to bring some of the possible causes and or aspects that may lead to the black specks on tablets during compression.

Resource Person: Masihuddin J.


  1. would you know what the final outcome was? we see very similar spot on our product

  2. Spots of the tablets in paracetamol not coming at the time of compression after storage spots of the tablet and colour variation occurring. But our sample was good and market tablets having problem what should be done.

    1. There are few points you have to check - the selected excipients are based on RLD or not, the storage condition as per RLD recommendation or not, is there residual sulfuric acid present in any API or excipients.

      You should follow RLD excipients and RLD recommended storage condition.

      You should also avoid residual sulfuric acid with carbohydrate excipients (e.g., lactose).

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