I have taken 0.25mg of ativan (lorazepam) at 5pm today, and at 10pm i've taken valerian root. could anything serious happen to me? should i look for an er?

No reason to worry: 0.25 mg is a low dose of Ativan (lorazepam) (which is often given in doses as high as 2mg). I recommend taking the lowest dose that works, but 2 mg is generally safe. Valerian root is extremely safe and relatively mild compared to Ativan (lorazepam). If you take both Ativan (lorazepam) and Valerian you can expect an additive effect; you will be more sedated than taking either alone, but it is not dangerous. No need to go to ER.

No: there will not be a reaction between this herb and low dose Ativan (lorazepam).