Zenith captured the £3.5 million SMA Nutrition business from Mediaedge:cia to add to the Wyeth Consumer Healthcare account it has handled since 1995.
Sarah Wood, the head of brand at SMA, said: "We're delighted to appoint ZenithOptimedia. In particular, it makes sense to draw on synergies with other Wyeth brands and any cost savings these may bring."
CHI & Partners won the Centrum account without a pitch off the back of scooping the Anadin ad account last October.
Sarah Gold, the joint managing director of CHI & Partners, who led the account win, said: "CHI & Partners is delighted to be strengthening its relationship with Wyeth and the opportunities this gives us to work on leading brands like Centrum."