European governments and the Obama administration are this weekend studying a "gamechanging" report on global drugs policy that is being seen in some quarters as the beginning of the end for blanket prohibition.

Publication of the Organisation of American States (OAS) review, commissioned at last year's Cartagena Summit of the Americas attended by Barack Obama, reflects growing dissatisfaction among Latin American countries with the current global policy on illicit drugs. It spells out the effects of the policy on many countries and examines what the global drugs trade will look like if the status quo continues. It notes how rapidly countries' unilateral drugs policies are evolving, while at the same time there is a growing consensus over the human costs of the trade. "Growing media attention regarding this phenomenon in many countries, including on social media, reflects a world in which there is far greater awareness of the violence and suffering associated with the drug problem," José Miguel Insulza, the secretary general of the OAS, says in a foreword to the review. "We also enjoy a much better grasp of the human and social costs not only of drug use but also of the production and transit of controlled substances."

Insulza describes the report, which examines a number of ways to reform the current pro-prohibition position, as the start of "a long-awaited discussion", one that experts say puts Europe and North America on notice that the current situation will change, with or without them. Latin American leaders have complained bitterly that western countries, whose citizens consume the drugs, fail to appreciate the damage of the trade. In one scenario envisaged in the report, a number of South American countries would break with the prohibition line and decide that they will no longer deploy law enforcement and the army against drug cartels, having concluded that the human costs of the "war on drugs" is too high.

The west's responsibility to reshape global drugs policy will be emphasised in three weeks when Juan Manuel Santos Calderón, the president of Colombia, who initiated the review, arrives in Britain. His visit is part of a programme to push for changes in global policy that will lead up to a special UN general assembly in 2016 when the scenarios of the OAS are expected to have a significant influence.

Experts described the publication of the review as a historic moment. "This report represents the most high-level discussion about drug policy reform ever undertaken, and shows tremendous leadership from Latin America on the global debate," said Kasia Malinowska-Sempruch, director of the Open Society Foundation's Global Drug Policy Program, which has described its publication as a "game-changer".

"It was particularly important to hear president Santos invite the states of Europe to contribute toward envisioning a better international drug policy. These reports inspire a conversation on drug policy that has been long overdue."

The report represents the first time any significant multilateral agency has outlined serious alternatives to prohibition, including legal market regulation or reform of the UN drug conventions.

"While leaders have talked about moving from criminalisation to public health in drug policy, punitive, abstinence-only approaches have still predominated, even in the health sphere," said Daniel Wolfe, director of the Open Society Foundation's International Harm Reduction Program. "These scenarios offer a chance for leaders to replace indiscriminate detention and rights' abuses with approaches that distinguish between users and traffickers, and offer the community-based health services that work best for those in need."

In a statement, the Global Commission on Drug Policy, which campaigns for changes in drug laws and is supported by the former presidents of several South American states, said that publication of the review would break "the taboo that blocked for so long the debate on more humane and efficient drug policy". The Commission said that it was "time that governments around the world are allowed to responsibly experiment with regulation models that are tailored to their realities and local need".

■ The open letter from the Global Commission on Drug Policy is signed by George P Shultz, the former US secretary of state; Paul Volcker, the former chairman of the US federal reserve, and the former presidents of Mexico, Chile and Colombia