AstraZeneca's slide helps push Britain's FTSE away from all-time high

* FTSE 100 down 0.6 pct

* Merck (Other OTC: MKGAF - news) trial success puts pressure on Astra

* BP top riser after smashing expectations

By Alistair Smout

LONDON, April 28 (Reuters) - Britain's top share index pulled away from all-time highs on Tuesday, weighed down by a drop in pharmaceutical stocks, although the market was supported by forecast-beating results from oil giant BP.

AstraZeneca (NYSE: AZN - news) was the top faller on the FTSE 100 , sliding 1.7 percent after U.S. rival Merck (Swiss: MRK.SW - news) & Co's diabetes drug met heart-safety requirements in a recent study.

Analysts said that this gave Merck a leg-up on rivals such as AstraZeneca, whose diabetes drug was recently required by U.S. authorities to carry information about the risk of heart failure.

Pharmaceutical stocks trimmed more than 9 points off the FTSE 100, the biggest weight on the index.

The FTSE was down 42.2 points, or 0.6 percent, at 7,061.76 by 0749 GMT, having touched a new record high at 7,122.74 during Monday trade.

Traders said the index could struggle to make headway ahead of a closely contested British election next week, which could see sectors such as utilities and banks come under regulatory pressure if the opposition Labour party takes office.

Centrica (LSE: CNA.L - news) , which has underperformed along with other domestic utilities this year on Labour's plans to cap bill rises, gained 1.4 percent after its chairman said it had made preparations in case it is approached with a takeover offer.

The FTSE 100's international exposure may shield it from much of the worst election-related volatility, and it has been supported by a recovery in beaten down oil shares.

BP rose 1.6 percent, contributing more than 5 points to the index, after it reported higher-than-expected profits thanks to a hefty increase in refining revenues that offset poor earnings from its oil production division.

The company reported a first-quarter underlying replacement cost profit of $2.58 billion, more than double expectations of $1.28 billion.

"To put this morning's number into perspective profits are still much lower from a year ago, down by 39 percent, but as with anything it's all about expectations and these were low," Michael Hewson, chief market analyst at CMC Markets, said.

"The extent of the beat does appear to have caught a lot of people by surprise." (Editing by Susan Fenton)