i only used 2 pens - the first one was fine, the second one was a nightmare of air and bubbles. it was like that little black stopper inside - the one that moves with the insulin's reducing volume - was stuck. it wasn't even level in my last pen. there was lots of air inside the pen - you could see it.
i called lantus and they said to take it back to the pharmacy. i took it back to the pharmacy and they called the lantus company. the company then wouldn't exchange my pen because it was for a cat and lantus isn't sold for use in cats, and because i was using a needle to poke into the stopper instead of the pen needles that are supposed to be used with the pen.
the pharmacist gave me a pen needle (that people are supposed to use with it) and i tried to express the air that way - which did work. it didn't solve the problem, though and it still kept getting stuck. then the final straw for me was when i was trying to withdraw insulin from the pen, and because punkin's on a large dose i was trying to adjust my hand to pull the plunger farther. the second i let go of the plunger, the suction inside the pen sucked the insulin right back out of the syringe into the pen. there went a string of bubbles and insulin back into the pen, right along with the lubricant inside of the syringe, contaminating the insulin. grrrr.
i switched back to the vial - punkin's on a big enough dose we use it up. but also the latest information (see the sticky on How to store and use lantus/levemir) says that if it's handled correctly lantus vials have been lasting up to 6 months. so perhaps even those of you and smaller doses would be able to use a vial.
at the time there was a thread about this problem and several people also had trouble with it. if you have trouble with any of it and are contacting the Lantus company, try not to mention you're using it for a cat or using needles to poke into the pen. that's a guarantee of no help from them.
