tobacco and snus when smoking was not possible. They also suggested the product name "Nicorette". Fernö began experimenting with nicotine gum in 1969, and quit smoking himself after one year of use. The first nicotine chewing gum was produced at AB Leo in 1971. The innovation was in the use of ion-exchange resin (polacrilex) in order to control the rate of release of nicotine during chewing. Fernö explained, "Putting nicotine into chewing gum is not an invention. Fixing the nicotine to an ion exchange resin and putting that in a chewing gum to enable the chewer to control the rate of release—that is an invention". The same year Håkan Westling, Professor of Clinical Physiology at Lund University, started the first clinical trials of the gum as an aid to smoking cessation at the university hospital. His findings were presented at the Second World Conference on Smoking and Health in London and were published in 1973, in the journal Psychopharmacologia together with an article by Fernö. Nicotine chewing gum was presented at the Third World Conference on Smoking and Health in New York in 1975, by Fernö in partnership with the British researcher Michael Russell from the Institute of Psychiatry, who pioneered the measurement of blood nicotine levels. Russell and his colleagues at the Addiction Research Unit at the Institute of Psychiatry became involved in further research into nicotine gum through randomised controlled trials funded by the British Medical Research Council and the UK Department of Health and Social Security. Nicorette was registered as a drug in Switzerland in 1978, in Canada in 1979, and in the UK in 1980. It was registered in Sweden in 1981. Initially the Swedish Medical Products Agency declined to approve Nicorette as a medicine because it considered smoking not an addiction, but a lifestyle choice; and the Swedish National Board of Health and Welfare regarded orally consumed nicotine products not as medicine but as foodstuffs. On January 13, 1984, Nicorette chewing gum was approved by the US Food and Drug Administration after a 34-month review. It was brought to the US market by Marion Merrell Dow under licence from AB Leo. In 2016, it was the third biggest selling branded over-the-counter medication sold in Great Britain, with sales of £66.0 million. Further product The Nicorette Patch was introduced to the market in 1991 and the nasal spray in 1994. In 1996, the FDA approved the