By Geoff Mulvihill THE ASSOCIATED PRESS An advertising agency that helped develop marketing campaigns for OxyContin and other prescription painkillers and a drugmaker announced separate agreements Thursday worth a total of $500 million to avoid going to trial on claims that they bore some responsibility for the nation’s opioid crisis. Publicis Health, part of the Paris-based media conglomerate Publicis Groupe, agreed to pay $350 million, part of which will flow to every state in the next two months, and most of which will be used to fight the overdose epidemic. Hikma Pharmaceuticals agreed to pay $115 million in cash and provide $35 million worth of an overdose reversal drug to state, local and Native American tribal governments. Publicis is the first advertising company to reach a major settlement over the…