Oximatrine isn't an herb. Though it was derived from plants, the isolated substance is a drug primarily used in China, and can have significant side effects as with any other drug. You can get the herbs from which the drug was derived, but it will be weaker in action. The relation of oximatrine to the original herb is like the relation of quinine to its herbal source or digitalis to its herbal source or opiates to their herbal source, opium. This isn't to say anything about whether it works or not or whether one should take it or not, just that it isn't a plant, it's one ingredient found in plants isolated and increased in strength, as with any drug originally from a plant source.
I had not heard of the herb. I did a PubMed lookup ad found this:
Capsule oxymatrine in treatment of hepatic fibrosis due to chronic viral hepatitis: a randomized, double blind, placebo-controlled, multicenter clinical study.
http://www.ncbi.nlm.nih.gov/pubmed/15484298
Effects of oxymatrine on experimental hepatic fibrosis and its mechanism in vivo.
http://www.ncbi.nlm.nih.gov/pubmed/15633229
And a full search gives over 180 citations.
http://www.ncbi.nlm.nih.gov/sites/entrez