Just over two years <a href="http://www.mediandesigns.in/pristiq-rash-qz41">desvenlafaxine pbs</a> CHICAGO, Aug 23 (Reuters) - Merck & Co's decision to suspendsales of its Zilmax cattle feed additive has caused such a surgein demand for rival Eli Lilly & Co's Optaflexx thatLilly is telling some new customers it cannot immediately supplythem, customers told Reuters.