If you mean those herbal tablets you could well damage your liver. Although you'd need to swallow quite a number of these before that happened it is still a possibility. In addition I've just discovered that the Hops (one of the active ingredients) apparently reduces sexual desire in men so I don't think I'll be taking these to help me stay calm on dates from now on!
I am not sure what Kalms are, are you referring to tranquillizers, because any type of overdose, often if trying to commit suicide will not work as the bodies instinct makes you wake and panic and seek help. If you suspect a possible overdose, get medical attention immediately