Codeine is a sedative that is also used in prescription cough syrup as a pain reliever and to make people sleepy. It can depress the respiratory rate, heart rate and blood pressure.
It was an overdose of codeine, mixed with drugs, that caused the death of DJ Screw. Big Moe, another Houston native and a protégé of DJ Screw, named albums "City of Syrup" and "Purple World" for the "drank" and died in 2007 of a heart attack at the age of 33. Many speculated that "sippin syrup" led to his death.
Rapper Pimp C, whose real name was Chad Lamont Butler, also died in 2007. According to the Los Angeles County Coroner's Office, Butler died of respiratory depression caused by the promethazine/codeine in his system, coupled with a pre-existing sleep apnea condition. Sleep apnea causes breathing to pause or go shallow during sleep.
It is still unclear exactly what happened to Lil' Wayne, with some people saying that he suffered from seizures while others have indicated that he might be back on "sizzurp" -- a topic of many of Wayne's songs.
The National Institute of Health lists seizures as one of the serious side effects of codeine. Overdosing on dextromethorphan, a main ingredient in cough medicine, can also lead to seizures.
Wayne, 30, whose real name is Dwayne Michael Carter Jr., was admitted to Cedars-Sinai Medical Center in Los Angeles Friday after suffering multiple seizures. Rumors of his imminent death began to swirl online after TMZ.com reported that he had been given last rites and his family was rushing to be by his side, after doctors had pumped his stomach three times in an attempt to flush substances from his system.
But Wayne's camp and the rapper himself quickly dispelled the rumors. Late Friday Wayne tweeted, "I'm good everybody. Thx for the prayers and love."
He was released from the hospital Monday, according to Mack Money, an associate of Wayne's record label Young Money.
Citing an anonymous source close to Wayne, Us magazine said Saturday that Wayne had overdone it with the "sippin syrup" concoction.
"He drank too much 'sizzurp' to get a better high," the source said. "He needs rehab but he's not close to death or anything. He's fine and just coming down off the high."
References to syrup are plentiful in Wayne's songs.
"Up in the studio me and my drank/Please let me be and let me do my thang/Thinkin about a certain ... certain somebody/That perfect somebody sexy purple body," he raps on "Me and my Drank."
In 2010, Wayne said that he gave up the drink. In a video posted online, the rapper said he was drinking Patron tequila and "RIP to the syrup."
Representatives for Wayne did not return ABC News' calls.
Dr. Jacqueline French, the president to of the American Epilepsy Society and a professor of neurology at NYU's Langone Medical Center, said there were several factors that could trigger seizures, including stress, if the brain was not receiving enough oxygen, not getting enough sleep and narcotics.
"Anything that compromises the brain can bring on a seizure," French said. "Certain drugs can lower the seizure threshold."
Dr. Dan Lowenstein, a professor of neurology at the University of California, San Francisco, said codeine, a sedative, would not necessarily be "pro-seizure" but that one of the concerns with cough syrup was that if it contained a stimulant, that could "offset the balance in the brain."
"There are a myriad of substances that can affect brain excitability and stimulants are one of them," Lowenstein said. "There are people who have a very low threshold for having seizures, and if they get exposed to the wrong combination of events, such as a stimulant drug and sleep deprivation, they then may develop a seizure and epilepsy."
Even still, the cause of Wayne's seizures remains unclear. But nonetheless, it has opened discussions for the dangers of "sippin syrup."