Regulators have issued warnings that thousands of packets of Nurofen Plus could have been mixed up with anti-psychotic drug, Seroquel XL.

The Medicines and Healthcare products Regulatory Agency (MHRA) issued the alert after three packets of Nurofen Plus were found containing individual blister packs of Seroquel XL in branches of Boots in the Victoria, Beckenham and Bromley areas of London.

The MHRA decided not to recall thousands of batches of the 32-tablet packs, but to urge “extra vigilance” to consumers, as the affected packets could be in pharmacies across the UK.

Nurofen Plus’ manufacturer, Reckitt Benckiser said “serious investigations” were underway to establish how the mix-up occurred, as Seroquel XL is manufactured by another drug firm, AstraZeneca.

A number of theories have been offered, but the drug makers are not believed to be at fault. The first suggestion hinted a simple mix-up at a wholesaler, but neither company is ruling out sabotage at this time.

Siân Boisseau, Director of Virgo Health, a public relations firm which represents Reckitt Benckiser, told the Guardian that there has been a “suggestion that the packets were deliberately put in the wrong boxes”.

The two drugs are very different. Reckitt Benckiser’s Nurofen Plus is one of the most popular brands of painkiller, whereas Seroquel XL by AstraZeneca is a prescribed anti-psychotic medicine to treat several disorders, such as schizophrenia, mania and bipolar depression.

People who accidentally take Seroquel XL may experience drowsiness and are advised to not drive or operate any tools or machinery until they know how the tablets have affected them. Other side effects include dizziness and headache.

The large capsules of Seroquel XL 50mg have gold and black packaging while the Nurofen Plus tablets are smaller and have silver and black packaging.

Ian Holloway from the MHRA's Defective Medicines Report Centre (DMRC), said: “People should check to see if they have any affected packets of Nurofen Plus. If you do, return them to the pharmacy where you bought them from”.

“If you have taken a tablet and you have any questions, speak to your GP,” he added.

A statement from AstraZeneca said: “Patient safety is the primary concern of AstraZeneca and the company is taking this issue seriously. AstraZeneca is collaborating with the MHRA and Reckitt Benckiser to investigate the root cause.”

Sanofi’s Indian unit, Aventis Pharma, is in talks over a takeover deal for the over-the-counter (OTC) division of Universal Medicare.

The deal is rumoured to worth around five billion rupees ($109m) and would see Sanofi gain around 30 of Universal Medicare’s brands, worth up to $25m in sales.

A Reuters source says the deal is expected to be completed within a couple of days.

India’s OTC market is growing at an annual rate of between 17-18%.

Sanofi has been branching into emerging markets and strengthening its consumer health business to offset the loss of sales to generic alternatives to its best selling products.

The company is not the first to target OTC markets in emerging markets. Last year Reckitt Benckiser acquired Paras Pharmaceuticals for $726 million, while Johnson & Johnson in May agreed to buy several Russian-market over-the-counter brands from India-based JB Chemicals and Pharmaceuticals.

Pharma companies’ best-in-class sustainability practices have been highlighted by the latest update to the Dow Jones Sustainability Indexes.

Eleven pharmaceutical companies were included in this year’s World Index update, eight of which were European-based, with Roche recognised as the ‘Supersector Leader’ in the Healthcare category for the second year running.

The companies, in alphabetical order, are Abbott Laboratories, Bayer, Genzyme, GSK, Johnson & Johnson, Novartis, Novo Nordisk, Novozymes, Reckitt Benckiser, Roche and sanofi-aventis.

Based on the Sustainable Asset Management’s (SAM’s) largest global analysis of corporate sustainability leadership, 48 companies joined the Dow Jones Sustainability World Index (DJSI World) this year, while 46 firms were deleted, including BP.

The DJSI include sustainability leaders from each industry on a global and regional level respectively. The annual review is based on a thorough analysis of corporate economic, environmental and social performance, assessing issues such as corporate governance, risk management, branding, climate change mitigation, supply chain standards and labour practices.

Roche has been included in the DJSI World since 2004. CEO Severin Schwan said: “Sustainability is at the core of our business practices and this positioning reflects our commitment to running our business in a way that is ethical, responsible and creates long-term value for stakeholders.

“Our ongoing sector leadership position will also provide an incentive to further develop our sustainability strategy while continuing to deliver innovative treatments for patients with unmet medical needs.”

Roche’s sustainability activities include efforts to improve energy efficiency, involvement with community charities, employee benefit programmes and the development of new approaches to bring sustainable healthcare products and services to patients around the world.