But codeine is not the only opioid scourge spreading across West Africa. Another painkiller, Tramadol, is fuelling widespread addiction - and as the BBC's Stephanie Hegarty found out, it may even be fuelling insurgency in the north-east.
When Mustafa Kolo, 23, takes the bright red pills he feels like he can push a tree. It's like his body isn't his. They obliterate the negative thoughts.
"When I take it, I forget everything," he says.
It's 10:00, Mr Kolo and his friend Modu Mohamed are with their boss, the commander of a vigilante unit set up to protect the city of Maiduguri from Boko Haram.
The young recruits are clearly uncomfortable.
'People have lost everything'
"How many did you take today?" I asked them.
"Today? None," came the reply.
Mr Kolo's eyes are dark and bloody red, he slurs slightly as he talks. Mr Mohamed is listless and distracted. His head is hanging between his bony shoulders.
It's obvious they're lying. The commander steps in and urges them to tell the truth.
"I used to take three to four when I first began taking it. But now I have reduced it to one or half," Mr Kolo says, unwilling to go further.
In this troubled town, thousands of people are addicted to Tramadol - the vigilante fighters, those displaced by the war and even the militants themselves.
The cheap opioid painkiller is meant to be used to treat moderate to acute pain. But, like most opioids, it is addictive - although just how addictive is a matter for debate.
The World Health Organization (WHO) says Tramadol is generally thought to have a "low potential for dependence relative to morphine".
But the epidemic of addiction erupting across West Africa could yet disprove that.
"The problem is really huge," says Marcus Ayuba, head of Nigeria's National Drug Law Enforcement Agency (NDLEA) in Borno state, bowing his head sadly.
"It's really huge."
Mr Ayuba runs a drug treatment centre in Maiduguri, the state capital where, by his own estimate, one in three young people are addicted to the drug - an epidemic which, he believes, can be traced back to a decade of war.
"People have lost everything," he says. "They are young people who were basically farmers, they've lost their farms, their homes."
"Parents have seen children killed in their presence," he adds.
Mr Ayuba says during counselling, people have told him, "What else can we do? We just want to get out of the world."
But the crisis didn't bring Tramadol to Nigeria. Mr Kolo started taking Tramadol in 2007, two years before the insurgency began.
At first, he says he took it to help him to work. It dulled the pain of physical labour while helping to keep him awake.
But now because of his addiction, he can't get work. Instead he volunteers with the civilian vigilante force.
"It really helps me in fighting Boko Haram," he says. "When I go into the bush, even the way I run, the way I walk, it's different. It gives me strength."
But the enemy too seems to have caught on to this trick.
"How many did you take today?" I asked them.
"Today? None," came the reply.
Mr Kolo's eyes are dark and bloody red, he slurs slightly as he talks. Mr Mohamed is listless and distracted. His head is hanging between his bony shoulders.
It's obvious they're lying. The commander steps in and urges them to tell the truth.
"I used to take three to four when I first began taking it. But now I have reduced it to one or half," Mr Kolo says, unwilling to go further.
In this troubled town, thousands of people are addicted to Tramadol - the vigilante fighters, those displaced by the war and even the militants themselves.
The cheap opioid painkiller is meant to be used to treat moderate to acute pain. But, like most opioids, it is addictive - although just how addictive is a matter for debate.
The World Health Organization (WHO) says Tramadol is generally thought to have a "low potential for dependence relative to morphine".
But the epidemic of addiction erupting across West Africa could yet disprove that.
"The problem is really huge," says Marcus Ayuba, head of Nigeria's National Drug Law Enforcement Agency (NDLEA) in Borno state, bowing his head sadly.
"It's really huge."
Mr Ayuba runs a drug treatment centre in Maiduguri, the state capital where, by his own estimate, one in three young people are addicted to the drug - an epidemic which, he believes, can be traced back to a decade of war.
"People have lost everything," he says. "They are young people who were basically farmers, they've lost their farms, their homes."
"Parents have seen children killed in their presence," he adds.
Mr Ayuba says during counselling, people have told him, "What else can we do? We just want to get out of the world."
But the crisis didn't bring Tramadol to Nigeria. Mr Kolo started taking Tramadol in 2007, two years before the insurgency began.
At first, he says he took it to help him to work. It dulled the pain of physical labour while helping to keep him awake.
But now because of his addiction, he can't get work. Instead he volunteers with the civilian vigilante force.
"It really helps me in fighting Boko Haram," he says. "When I go into the bush, even the way I run, the way I walk, it's different. It gives me strength."
But the enemy too seems to have caught on to this trick.
An army of addicts
A former militant fighter is sitting in a soft, lilac coloured Hawaiian shirt.
The 21-year-old is in the custody of the Nigerian army after running away from Boko Haram in January.
For four years, he lived in a forest camp where there wasn't enough food or water - but there was Tramadol.
"When you are going for a military operation you will be given it to take, otherwise if you take it you will be killed," he says.
"They told us when you take it you will be less afraid - you will be strong and courageous."
The drug was once plentiful, but in the past few months, as the Nigerian army closed in on their camps, supplies became scarce.
Tramadol was reserved only for leaders and those going into battle. The former fighter believes they were all addicted.
The idea of an army of Islamist militants tanked up on opioids and sent out to kill is terrifying, and Mr Ayuba says believes it has contributed to the brutality of this conflict.
"Nobody has the natural will to take someone's life. Drugs are always there to give you the push," he says.
Then there are the women who have escaped from Boko Haram and now find themselves addicted to drugs.
One 16-year-old told him the militants would drug girls when they started crying.
"When she escaped she was looking for something to knock her out," he says.
A former militant fighter is sitting in a soft, lilac coloured Hawaiian shirt.
The 21-year-old is in the custody of the Nigerian army after running away from Boko Haram in January.
For four years, he lived in a forest camp where there wasn't enough food or water - but there was Tramadol.
"When you are going for a military operation you will be given it to take, otherwise if you take it you will be killed," he says.
"They told us when you take it you will be less afraid - you will be strong and courageous."
The drug was once plentiful, but in the past few months, as the Nigerian army closed in on their camps, supplies became scarce.
Tramadol was reserved only for leaders and those going into battle. The former fighter believes they were all addicted.
The idea of an army of Islamist militants tanked up on opioids and sent out to kill is terrifying, and Mr Ayuba says believes it has contributed to the brutality of this conflict.
"Nobody has the natural will to take someone's life. Drugs are always there to give you the push," he says.
Then there are the women who have escaped from Boko Haram and now find themselves addicted to drugs.
One 16-year-old told him the militants would drug girls when they started crying.
"When she escaped she was looking for something to knock her out," he says.
Smuggled by gangs
At the choked port of Lagos, an officer from the NDLEA orders men to break open a container with a crow bar. Stacked from top to bottom are boxes of an over-the-counter painkiller, but hidden behind them are thousands of packets of Tramadol.
The brand is Super RolmeX. On the packet it says "Made in India, for export only". That is because the dosage - at 225mg - is more than twice what is legal in most countries.
It says it's manufactured for Sintex Technologies Ltd in London, England, but a quick search on the UK companies register online shows that company was dissolved in 2012.
There are six containers and millions of tablets in this shipment alone.
The UN say Tramadol is being smuggled into Africa from South Asia by international criminal gangs, with yearly seizures in sub-Saharan Africa rising from 300kg (661lb)per year to more than three tonnes since 2013, according to a report in December.
So with abuse clearly happening in places like Nigeria, it's hard to understand why Tramadol is scheduled two ranks below oxycontin, morphine or high dosages of codeine by the US.
"It could be that it's a weak opioid," says Dr Eric Stein, an expert in drug abuse.
"At the end of the day the ready availability of stronger opioids make it unnecessary [for those trying to get high]" he says.
"If you're looking to get drunk, do you drink a beer or do shots?"
At the choked port of Lagos, an officer from the NDLEA orders men to break open a container with a crow bar. Stacked from top to bottom are boxes of an over-the-counter painkiller, but hidden behind them are thousands of packets of Tramadol.
The brand is Super RolmeX. On the packet it says "Made in India, for export only". That is because the dosage - at 225mg - is more than twice what is legal in most countries.
It says it's manufactured for Sintex Technologies Ltd in London, England, but a quick search on the UK companies register online shows that company was dissolved in 2012.
There are six containers and millions of tablets in this shipment alone.
The UN say Tramadol is being smuggled into Africa from South Asia by international criminal gangs, with yearly seizures in sub-Saharan Africa rising from 300kg (661lb)per year to more than three tonnes since 2013, according to a report in December.
So with abuse clearly happening in places like Nigeria, it's hard to understand why Tramadol is scheduled two ranks below oxycontin, morphine or high dosages of codeine by the US.
"It could be that it's a weak opioid," says Dr Eric Stein, an expert in drug abuse.
"At the end of the day the ready availability of stronger opioids make it unnecessary [for those trying to get high]" he says.
"If you're looking to get drunk, do you drink a beer or do shots?"
Religion plays a role
So why is it so prevalent in Nigeria? Firstly it is cheap - in Nigeria it's about $0.05 for 200mg as opposed to about $2.50 in the US, and secondly its ability to help people work. Across Africa, many people rely still on manual labour to get paid.
Mr Ayuba believes religion may have a part to play as well. Alcohol is forbidden in the majority Muslim communities of north-east Nigeria, but there is less of a taboo around prescription drugs.
Despite anecdotal evidence, the WHO has so far resisted putting international controls on its trade.
There are fears limiting access to the drug would cut people off who really need it: it is one of the few painkillers widely available to treat pain for cancer patients.
It can also be brought in pretty easily to crisis and emergency situations, says Gilles Forte, secretary of the group responsible for reviewing Tramadol at the WHO.
"If it's scheduled it becomes difficult to move it from one country to another," he explains.
But as long as it is so freely available the addiction crisis will continue. As it is, Mr Ayuba can only manage a fraction of the cases he is presented with every day.
Though they would like to, the parents of Mustafa Kolo - the young vigilante - cannot afford to send him to the drug treatment centre.
"I used to dream about grandchildren from him. Now, I see that I have lost," says his father.
"All my country has lost, because of what he is doing."
So why is it so prevalent in Nigeria? Firstly it is cheap - in Nigeria it's about $0.05 for 200mg as opposed to about $2.50 in the US, and secondly its ability to help people work. Across Africa, many people rely still on manual labour to get paid.
Mr Ayuba believes religion may have a part to play as well. Alcohol is forbidden in the majority Muslim communities of north-east Nigeria, but there is less of a taboo around prescription drugs.
Despite anecdotal evidence, the WHO has so far resisted putting international controls on its trade.
There are fears limiting access to the drug would cut people off who really need it: it is one of the few painkillers widely available to treat pain for cancer patients.
It can also be brought in pretty easily to crisis and emergency situations, says Gilles Forte, secretary of the group responsible for reviewing Tramadol at the WHO.
"If it's scheduled it becomes difficult to move it from one country to another," he explains.
But as long as it is so freely available the addiction crisis will continue. As it is, Mr Ayuba can only manage a fraction of the cases he is presented with every day.
Though they would like to, the parents of Mustafa Kolo - the young vigilante - cannot afford to send him to the drug treatment centre.
"I used to dream about grandchildren from him. Now, I see that I have lost," says his father.
"All my country has lost, because of what he is doing."
