I've tried an extra 1/2 at night a couple of times, on the vet's ok. It seemed to be ok. I'm not sure if the dose is inflexible as it's not a drug but a supplement (?). There are no negative reports are there, just positive and some people who say it didn't work, not that it caused problems. Works a lot better than valerian and skullcap with Swampy anyhow.