In December, Uruguay became the first nation in the world to legislate for the production, sale and state regulation of marijuana. Many hope that when the law takes full effect next year, fewer people will use a cheap, highly addictive cocaine derivative called "pasta base". Others fear the opposite.
At 17:00 in Malvin Norte, a neighbourhood in the east of Montevideo, the pasta base addicts are beginning to emerge. Young men in dirty clothes walk the streets uneasily, adopting the look of the hunted. One of them picks through a rubbish bin. Two more, one a young woman, are still asleep under a tree, surrounded by litter.
At 36, Carlos Rodriguez is older than many of the other addicts. And he has had enough. He is going to call his mother, to ask her to help him get into drug rehabilitation.
"I want to change my life," he says, his eyes bloodshot and unfocused. "I still have some lucidity, some brain power, although not many addicts do. I want help."
Carlos used to be a drug dealer. In those days, he never touched pasta base himself. Then his son died.
"I was in such pain, and I was fighting all the time with my wife. That's when I started to smoke it," he says.
Pasta base, also known as cocaine paste or coca paste, is a by-product of processing raw coca leaf into cocaine. It is produced in Peru, Bolivia and Colombia, and appeared in Uruguay and neighbouring Argentina during the economic crisis of 2002, offering momentary euphoria in desperate times.
More than a decade later, its impact is felt most acutely in Uruguay's working class communities. Pasta base users are estimated to make up less than 1% of the country's population of 3.3 million, but in communities like Malvin Norte, the proportion may be four times higher.
Jose Pedro Prieto, a graduate student at the Instituto Clemente Estable who has researched pasta base, says it is often adulterated with caffeine, which gives it a higher stimulant effect than cocaine alone.
"Users get a very high euphoria," he says. "But this is followed by feelings of sadness and anxiety, which in turn lead to a strong desire to continue smoking."
Carlos Rodriguez knows only too well the potency of pasta base.
"I don't know any drug that's more powerful," he says. "There's never an end to how much you want to consume. If you take a gram of cocaine, that's enough. With pasta base if you consume 1g, 3g, 20g, 30g, you still want to take more. And it's not a sociable drug. Pasta base is a drug that creates enemies."
Carlos speaks to his mother on the phone, and she agrees to help him. He will go to her house in the morning, and she will put him on the bus to travel to a drug rehabilitation centre in the north, near Uruguay's border with Brazil.
Close to the main crossroads in Malvin Norte, Silvia Siage runs a small store selling basic food products, items of clothing, and children's toys. But it's not easy to see the range of goods, because no one is allowed inside. Silvia serves customers through a barred window and there are grills and padlocks on every door.
Life changed for Silvia one afternoon in 2010.
"What happened here was just horrible. Two men came in screaming, 'We want the money, we want the money.' They didn't wait, they just shot two bullets at my husband and one at me," she says. "They were completely under the influence of drugs. I imagine it was pasta base, because that's the most common drug around here. We are completely surrounded by addicted people, and now I have to sell my products through this window."
Silvia's husband, Jorge Lemos, was killed in that attack. And she still has difficulty straightening her arm as a result of her injuries.
Although Uruguay is one of the safest countries in Latin America, it has seen a rise in crime associated with narcotics. In a survey of more than 8,500 prisoners, a third said they had committed crimes under the influence of alcohol or drugs, and nearly half of those had consumed pasta base. Users may be a tiny minority, but they are often associated with theft and robbery. Although pasta base is a cheap drug at $1 or $2 a hit, addicts need multiple doses.
The government hopes the legalisation of marijuana will increase security in communities like Malvin Norte. By allowing adults to grow their own cannabis or buy a maximum of 40g a month from a pharmacy, supporters of the new law believe it will separate the marijuana market from more problematic drugs.
"The largest market for drugs in Uruguay is marijuana. But to get it, people have to access the illegal market - the places where pasta base is sold. If someone goes to get cannabis and there isn't any, they can end up buying pasta base instead," explains Eduardo Bonomi, Uruguay's Minister of the Interior.
So, when the new law is fully implemented in the next year, it will mean fewer people will come into contact with pasta base. And taking cannabis out of the illicit market will hit the drug traffickers hard. That is the theory.
Silvia Siage does not buy it. She says the "bocas" - the street-corner drug sellers - will not go away. "At the pharmacy there will be a limit to how much marijuana you can buy," she argues. "And in the bocas there is no limit."
Cristina Chevalier works with Madres de La Plaza, an NGO [non-governmental organisation) set up in 2006 to challenge the drug dealers selling pasta base and report them to police. She says they have become "a natural part of our landscape".
"In one block in the centre of Montevideo, there can be 10 points of sale for drugs," she says.
The legalisation of marijuana will encourage more young people to use it, she says, and then from marijuana they will graduate to harder drugs like pasta base.
Others are convinced marijuana can be a force for good. Milagros Gallero was a pasta base addict who used cannabis to wean herself off the harder drug.
"When I got withdrawal symptoms from the coca paste, I smoked marijuana to relieve them. I know a lot of people who have used it like this. It works."
Milagros has a different relationship with drugs now, and she is proud Uruguay is the first country in the world to legalise marijuana.
"Prohibition of drugs hasn't led to a decrease in consumption. We don't know if the new law regulating marijuana will impact problematic drug users," says Eduardo Bonomi, the Minister of the Interior. "What we do know is that when we strictly regulated the sale of tobacco and ran an education campaign on the harm it causes, we saw a decrease in the use of tobacco."
So what will Bonomi count as a successful outcome from marijuana legalisation?
"If fewer people access the black market, and if there's a reduction in the number of people consuming pasta base," he says.
And what happened to Carlos Rodriguez, the pasta base addict from Malvin Norte who said he was on his way to drug rehabilitation? This time, according to his mother, Rosa, he did not make it.
"He didn't turn up. I feel desperate, and the rest of the family is putting me under pressure to abandon Carlos. They don't believe in him. I'm the only one to support him now."