Around 70 per cent of Swiss firms, including Novartis and Roche, have already adopted the guidelines, according to the SwissInfo news service.
The code - which came into effect on January 1 - also prohibits pharmaceutical firms from paying for holidays for doctors and their spouses. This is already illegal under Swiss law.
The drug industry has come under fire in recent years for a number of its drug promotion practices, including the sponsoring of doctors' training courses, which the code also bans.
A Swiss law banning the practice of offering incentives to doctors to prescribe drugs came into effect in 2002. But Swissmedic, the government agency responsible for enforcing it, says it has since issued a number of warnings to companies that have broken the law.