How to tell if your asthma inhaler is empty

[watervole]

 A problem that plagues asthma sufferers (including myself) is how you know if your inhaler still has medication in it.  There's no indicator; the medication is almost tasteless and has no colour.  They continue 'working' when all the medication is gone (or at a level that is too low to be effective)

I've seen suggestions that they are out of medication when the cannister floats, but apparently that's not accurate. 

I've decided to tackle this by weight.

A full Salmerterol inhaler (cylinder only) weights 21 grams on my kitchen scales.  1 dose = 25micrograms medication + 125 milligrams propellant.

Each inhaler has 120 actuations.  This gives a weight loss of 15 grams before the cannister is effectively empty.

So, when my inhaler weights 6g, then I will know it is empty.
 

I found a handy medical site that already had the figures for Ventolin.

A Ventolin (Salbutamol) inhaler weighs 37g when full and 25g when empty

 

Salamol - my new reliever in 2023) weights 16gm (cannister only) when full. A full Salamol® inhaler (inc all bits including cap) weighs 26g, and an empty one weighs 17g. (cannister only will weight 7g when empty)

 

Hopefully, I'm not the only person who will find this useful.