Modulation of activities and mRNA expression of cytochrome P450 isoenzymes in rat liver by Sophora flaveacens and coadministration with Veratrum nigrum Valuation on analgesic, expectorant and antitussive effects of compatible use of Aconiti Radix Cocta and Fritillaria cirrhosa or Fritillaria thunbergii Study on efficacy of compatibility between Aconiti Radix Cocta and Pinelliae Rhizoma on basis of uniform design method