I should add, combining remedies isn't simple, and you should consult an herbalist or naturopath if you don't know natural remedies all that well.
Actually, you could take St. John's Wort with it, but that's for depression, not anxiety. 5-HTP is for both. Take it in divided doses, and the main thing to avoid is any med that also affects serotonin. Herbs, on the other hand, are best used in combination because they're not as strong as meds, they work in a way the body recognizes, and they work synergistically much better than singly.. Same with amino acids. There's a good book on 5-HTP by, I think, Michael Moore, and a good book on natural remedies for this stuff called Natural Highs by Hyla Cass, a psychiatrist at UCLA.
alcohol, cold medicines, other antidepressants (SSRI, SNRI, MAO, Tricyclics), other natural anti depressants like st johns wort, nasal degongestants, there are a few more google it and there is alot of info about it