You can always employ behavioral changes before progressing to pharmacologic agents. With respect to the latter, Ginger and B6 are good adjuncts to Reglan, Phenergan, and Zofran. A good trick, which I use with my patients, is to give the Reglan per vagina rather than PO.
If pharmacologic agents fail, then you must ensure that another etiology is not in play (thyroid, pancreas, etc). Be cautious with GD Tubes or PICC lines as new prospective data supports long existing retrospective findings confirming high rates of comlication.
Best of luck!