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Good evening America, I talked to @DataDrivenMD down below about thread jacking his thread for a lesson in filling a vial. #Thread 
https://twitter.com/datadrivenmd/status/1352757557937332224
https://twitter.com/datadrivenmd/status/1352757557937332224
Let’s start with vial.
The vials are made of a high silica glass that is blown into shape via machines. This mass production means that some vials are not like the others.
Due to these differences, the vials will have a “Head Space” in them. As an example a 3oz vial will actually hold 3.5oz to make sure they will hold the 3oz they are meant to.
Vials are filled via 2 main methods, by weight & volume by time. Let’s start with the one not being used here. Weight.
The vial comes down a conveyer belt & stops below an injector needle. The needle drops in & a calibrated pump fills the vial. This pump is calibrated using a specific gravity calculation to get the proper volume. The pump dose not always pump the same volume...
... so it pumps a bit extra just in case #OverFill
This method is old and slow in today’s world of pharma manufacturing.
Fast production now uses a volume by time filling method. In this method, the vial never stops moving, increasing throughput on a production line.
In this method of filling, the needle travels with the vial as it moves down the conveyer belt. A liquid viscosity calculation is made and that dictates how long, time wise, the fill needle is injecting into the vial.
This method is very accurate but to make sure what is promised is delivered, a bit more time is added to the fill. #OverFill
The faster the production line runs with this method, the less accurate the fill can become.
Now you know why’s there’s #OverFill in the vials and why it cannot be counted on as a full dose. Thanks for letting me thread Jack and that’s my @TEDTalks
