McKesson and Spectro Industries agreed to merge.

Directors of McKesson and Spectro voted unanimously to merge the two large distributors of drug and health-care products. The agreement calls for McKesson to pay $20 a share for Spectro’s common stock for a total of about $161 million. McKesson, based in San Francisco, is a leading distributor of drug and health-care products, wine and spirits, bottled water and chemicals. Spectro is based in Jenkintown, Pa. The acquisition will be accomplished by a cash tender offer set to begin as soon as possible, the companies said.