SmithKline Beecham led the retreat. It was, it seems, the main target of the disenchanted American investors, falling 14p to 598p. In sympathy, Zeneca, already fragile on the failure of the long-mooted Swiss bid to materialise, dropped 16p to 1,117p and Medeva lost 6p to 262p.
Glaxo Wellcome, facing the additional uncertainty of rivals to its asthma drug, gave up 10p to 770p.
Zeneca's new oral asthma treatment has been accepted for filing by the US Food and Drug Administration and little ML Laboratories, up 11p at 181p, is to said to have a new drug on the launch pad.
But bid target Fisons, heavily dependent on its asthma treatments, gained 2p to 257.5p as it at last sold its laboratories supplies division; British Biotech put on 19p to 572p.
But suggestions that Cantab Pharmaceuticals was encountering increasing losses lowered the shares 30p to 160p. There are also fears the reported negotiations will not, as some hope, lead to a bid.
Smith & Nephew, the healthcare group where American takeover rumours have stuck as close as any of its Elastoplast dressings, added to the gloom, falling 1.5p to 193.5p, as some speculators lost patience.
The drug reverse occurred as the rest of the stock market wilted with the lingering presence of the August bank holiday reducing trading to a path- etically low level. The FT-SE 100 index tumbled 22.3 points to 3,502.6.
The sad state of affairs was reflected by the TI engineering group. It was said that a buying order for a relatively modest 250,000 shares left the market short, pushing the price 6p higher to 435p.
The $300bn US banking merger had a limited impact on UK banking shares, pushing two of the more vulnerable bid targets higher; Standard Chartered rose 4p to 426p and Royal Bank of Scotland, helped by James Capel support, added 6p to 463p.
Reuters, the information agency, fell 11p to 577p as it was realised that efficiency moves and job losses at the new giant would cut the demand for trading screens.
RTZ, the mining giant, fell 6p to 885p after it denied market rumours in Australia it was intending to bid for the outstanding 49 per cent of its CRA associate.
As Barclays de Zoete Wedd cut its profit forecast ahead of tomorrow's figures, Ladbroke fell 2.5p to 164.5p, and Kingfisher weakened 5p to 463p as a rumoured 4 million shares sought a home.
Electricities managed the occasional flicker of interest as stories continued to circulate that US giants were poised to strike. But any action will obviously have to await the Whitehall verdicts on the present round of bids - expected this week.
Southern Electric, seen as the most likely US victim, gained 11p to 764p and London Electric 7p to 816p.
Hambros, the securities group, was back in the bid frame, up 5.5p to 199p. Some estimate a value of 250p a share without any contribution from its Hambro Countrywide estate agency offshoot. Lloyds Chemists was another old takeover favourite in demand. The shares edged forward to 240p, up 5p. The troubled Brown & Jackson retailing group rose 3p to 29p.
Queens Moat Houses managed a 0.5p rise to 8.75p on rumours the reclusive Barclay brothers, who have considerable hotel interests, were having a close look at the group. It was unclear whether they were supposed to be thinking of bidding or merely buying properties from QMH.
PetroCeltic, the Irish resources group, fell 1p to 42p. The shares could enjoy a run today.; after the market closed, Marathon, the US oil giant, confirmed it had struck it rich off the Irish coast with natural gas flowing at a daily rate of 23.3 million cubic feet. PetroCeltic receives royalties on gas sales which will be made mainly to Eire.
Ivernia West, the Irish zinc and lead group, rose another 4p to 72p on continuing speculation that Minorco, the South African group already sitting on nearly 25 per cent, wants to mount a bid for full control.
Courtyard, a shell company running a handful of London wine bars, could give ground; it announced after hours that talks with the Wiggins property group had been broken off. The shares are 9p. Wiggins planned to take a stake in Courtyard which would run certain catering sites.
Biocompatibles, a little healthcare group, jumped 22p to 188p as it received approval to market its soft contact lens, Proclear, in the US. Kunick, the amusement machines group, rose 2p to 22.5p.
o Farringford, the leisure group with just one hotel, has at last put together an expansion deal. It is moving into the pub business by managing 210 tenanted pubs owned by the Pub Estate Co, a new concern that acquired 230 former S&N pubs. Trevor Hemmings, a director of S&N, is a leading player at the Pub Estate Co - and his Northern Trust has a big stake in Farringford. Shares in Farringford rose 1p to 10p.
o AIM dealings are expected to start today in Belcanto, which supplies support vessels for the offshore industry. The shares were last traded at 48p on the 4.2 market. The company's stockbroker is Branston & Gothard.
Also on its way to AIM is Omnicare, a healthcare group that is offering shares at 60p through stockbroker Astaire. Dealings are due to start next week.