AstraZeneca shares hobbled by arthritis drug In the wider market, the FTSE 100 also fell as worries over America's so-called "fiscal cliff" returned to the forefront. Federal Reserve chairman Ben Bernanke cautioned the central bank could not avert the potential harm caused by the cliff, a package of tax increases and spending cuts that kicks in next year and threatens to push the US into recession unless politicians can negotiate a compromise. The blue-chips ended the day 16.24 points lower at 5,929.61, ending six consecutive trading sessions of gains. Miners were a focus, with analysts at JPMorgan Cazenove optimistic on the prospects for the sector next year. They argued that conditions should be more "supportive" in the first half, in part because of the smooth leadership handover in China. Rio Tinto, up 27½p at £33.38½, was the broker's pick of the miners. Lower down the scale, there was speculation that India's Jindal Steel and Power had hired NM Rothschild as an adviser and was close to making a 130p-a-share bid for Afferro Mining, which dipped 1¼ to 77¾p. Afferro said earlier this month it was in talks that could result in an offer for the company, or a strategic investment. Back with the blue-chips, the heaviest faller was oil and gas services business Wood Group, despite the company reassuring the market that its performance for the year should meet expectations. However, Canaccord Genuity noted the slowing pace of headcount growth in its engineering division, adding that "this would imply a top-line engineering slowdown to high single-digit revenue growth next year," from about 25pc this year. Wood Group lost 35 to 733½p. A downgrade at Bank of America Merrill Lynch put pressure on events and publishing group Reed Elsevier. The broker cut the company to "underperform" from "neutral," arguing the group's valuation does not account for the risks posed by government drives to provide free access to publicly funded academic research. Scientific publisher Elsevier comprises 50pc of the group's profits. Reed shares slid 7½ to 634½p. Meanwhile, Numis analyst Steve Woolf reckoned investors should snap up shares in testing group Intertek because of management's potential to boost shareholder returns through takeovers. "We maintain a view that acquisitions are the most likely use of capital, and that the scope for larger strategic deals is likely to add greater value than is currently reflected in the share price," Mr Woolf said. He lifted his rating to "buy" from "hold," helping Intertek shares put on 12p to £30.84. Egyptian gold miner Centamin plunged an eye-watering 25 - 47.4pc - to 27.7p after halting operations at its principal asset, the Sukari mine, because of a dispute over fuel as well as an unexpected demand for government approval for exports of the precious metal. The news from FTSE 250-listed Centamin also knocked shares in rig group Capital Drilling, which tumbled 10 - 37.7pc - to 16½p. Centamin is one of its biggest customers and Capital said that "should the ceasing of operations persist this will have a substantial impact on current market consensus revenues and earnings." Liberum Capital noted that Egypt accounts for between 20pc and 25pc of Capital's revenues, with the majority of the group's drills in the country with Centamin, Elsewhere on the mid-cap index, Kenmare Resources, which digs for the mineral zircon in Mozambique, was weighed down by a bearish update from Australian peer Iluka Resources. Iluka said it is likely to sell 205,000 tonnes of zircon this year, at the bottom end of the 200,000 tonne to 400,000 tonne range the group guided in July. Kenmare shares dipped 1.12 to 30.05p. Towards the other end of the FTSE 250, UBS drew investors" attention to equipment rental group Ashtead, one of the broker's 16 "stocks to watch" next year due to its exposure to a potential US economic recovery. Ashtead posted record first-half pre-tax profits of £141m, excluding one-off items, on Tuesday, boosted by growing demand from US construction companies. Ashtead shares put on 7½ to 398½p. Finally, National Express trundled up 7.7 to 187.9p after confirming it was on course to meet its expectations for 2012.