They work the same post op. Althought since my surgery I have become allergic to penicillin so be aware that is a very slight risk! I find that in contrast to food which we malabsorb, tablets seem to have a stronger effect that previously. With painkillers for example I used to take di-hydra-codeine on a daily basis pre-op, now I can't tolerate it, it makes me itchy all over and makes me feel quite out of it.