Although your friend has suggested a very well-intentioned and risk preventative rule, to avoid herb and drug combinations, that precautions is not always required. Let's take a look at valerian, and see where the problems might be. As it turns out, there has been a fairly significant amount of recent research into valerian, and its potential for drug interactions.

It has been a common theme to believe that there might be a potentiation of effect between valerian and sedatives like alcohol or Valium or Haldol, but close observation revealed no interaction of any sort.

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15901352

Most interactions involve disturbances of rates of metabolizing drugs in the liver, and a close examination of that found that valerian had no effect on common liver enzymes.

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15900287

In contrast, another study found modest effect on enzymes 2D6 and 3A4, but concluded that "typical doses of valerian are unlikely to produce clinically significant effects on the disposition of medications dependent on the CYP2D6 or CYP3A4 pathways of metabolism."

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15328251

So, I'm inclined to believe that if there is any interaction in the liver, it is modest, and not of any real concern. But then, we have to consider the activity of the drug itself. What does valerian do?

Well, it binds to melatonin receptors, and presumably agonizes them, "supplementing" your own melatonin, but it also hits a few serotonin receptors, including ones in the gut.

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15636177

Looks okay so far. But what about the anxiolytic effect, the GABA-ergic one? There might be a problem there. Because of the GABA-receptor binding, people who undergo a general anaesthetic may have additive sedation. So, you must reveal your use of valerian if you contemplate surgery.

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=14742369

The only drug you list where there seems to be an obvious clash is the "Ativan as needed". You may experience additive sedation, if you use Ativan before the valerian has worn off.

So, in this specific case, I am not concerned. However, it is always important to treat herbs as drugs. Your body may not like the combination, regardless of the science. I had a paradoxical reaction to valerian, and was unable to sleep at all. Brains and bodies differ.

One comment about valerian.....for some people, it tends to work better after a week or so has gone by. I wouldn't use it more than a maximum of 3 months. And then a holiday of minimum 4 weeks.

I hope I covered everything.

Lar