Celesio's Chief Executive Fritz Oesterle, who has had a strained relationship with the company's majority shareholder, is stepping down after more than 12 years in office.

"Fritz Oesterle ... will retire from his office in amicable mutual agreement with the supervisory board as of June 30," the German drugs distributor and pharmacy operator said in a statement on Wednesday.

Celesio's dealings with the German industrial and retail conglomerate Haniel, which holds just over 50 percent in Celesio, have not been easy.

Celesio's management has been frustrated by receiving mixed messages from Haniel about how much in Celesio it plans to hold in the future, sources close to Celesio have said.

Talks between Shanghai Pharmaceutical and Haniel over the possibility of the Chinese company acquiring a large stake in Celesio have cooled, sources told Reuters last month.

In 2009, Oesterle ruffled the feathers of Haniel's management by the way he managed the acquisition of Brazilian drugs wholesaler Panpharma, but subsequently managed to smooth over the rift.