Its largely a matter of the quality of the amp. In my years of practice, I have never turned a U.S. made amp of any drug, upside down, and had it spill. I have however used foreign amps, doing the same, & had them spill. I've been doing this a long time. While it should work one way, in my experience it does not always. Therefore it is generally best to learn to withdraw every last drop w/out having to invert the amp. This is of course IF you are new to this. If you have experience you know the answer to question as it relates to you. I generally always do not invert foreign amps. If it is a U.S. medication, & therefore all I would adminster to someone else, I will invert. For two reasons. One, I've never had one spill, & two, it is considered to be proper procedure. Oh, & make sure you tap the glass above the score, if all the oil does not fall that way, hold it by the head a shake in a snapping motion downward. I.E., make sure you get all of the oil out above the score.
Rex Feral.