Syria has witnessed a large rise in the use and manufacture of amphetamines as fighters on both sides of its civil war use the drugs for stamina in battle.
The conflict has turned it into a major consumer and exporter of the drugs, which are said to generate hundreds of millions of dollars in profits each year. The main stimulant in question is Captagon, the former brand name of a drug first used as an antidepressant in the West in the 1960s.
Government forces and rebel groups accuse each other of using Captagon to fight prolonged battles without sleep. The pills, which many ordinary Syrians are also increasingly turning to, sell for between $6 and $30.
Captagon is often made by amateur chemists in makeshift laboratories. Production is cheap and simple, requiring "only basic knowledge of chemistry and a few scales", according to Ramzi Haddad, a Lebanese psychiatrist.
"It gives you a kind of euphoria," he said. "You're talkative, you don't sleep, you don't eat, you're energetic."
A drug control officer in the central city of Homs said he had observed the effects of Captagon on protesters and fighters held for questioning. "We would beat them, and they wouldn't feel the pain," he said. "Many of them would laugh while we were dealing them heavy blows."
The reports came as the United States Secretary of State, John Kerry, continued to put pressure on Syria's warring sides to attend an international peace conference in Geneva that is due to start on January 22.
Diplomats fear the talks may be fruitless, because of the insistence of rebel factions that President Bashar al-Assad cannot be allowed to stay in power.
At a meeting of the US-led "Friends of Syria" group in Paris this week, Ahmad Jarba, the leader of Syria's opposition National Coalition, reiterated that Assad and his family could have no role in the country's future.
- additional reporting AP