PAM is a waste of money imo. You can get the same results buy spending around $10-$15 and get 4L of mite spray.
Go to your local drug store and purchase NIX lice cream rinse. Not shampoo but the cream rinse. Should cost around $8-$10 for 56g/59ml. Same active ingredient as PAM 1% permethrin.
http://www.nixlice.com/about.php
Now purchase 4l of distilled water. Distilled water helps the solution last longer. Add the Nix to the entire 4L of water and shake well until mixed thoroughly.
Lastly buy a smalll spray bottle and your set. Keep the mixture in a cool dry place and it should be active for up to one year.
Good luck,
P.S- I know some will dissagree with this but I have used this process for years with great reults. I had one mite infestation a few years back and have been mite free since using this method.
Gavin