Rick Ross has blamed his seizures on "sleep deprivation," but he frequently writes rhymes about purple drank or sizzurp.
Lyrics from Rick Ross' "The Boss":
Sizzurp is most commonly made from promethazine with codeine syrup, a mixture often prescribed as a cough syrup, mixed with Mountain Dew or Sprite and a handful of Jolly Ranchers.
The combination can be lethal, especially when mixed with alcohol or other drugs:
From the Wikipedia article for "Purple drank":
Purple drank is a slang term for a recreational drug popular in the hip hop community in the southern United States, originating in Houston, Texas. Its main ingredient is prescription-strength cough syrup containing codeine and promethazine. Cough syrup is typically mixed with ingredients such as Sprite soft drink or Mountain Dew and pieces of Jolly Rancher candy. The purplish hue of purple drank comes from dyes in the cough syrup.
Erowid.org, a prominent drug forum, has a fairly detailed report of what a sizzurp trip is like:
This report from 2010 details an anonymous 130-pound male doing 20 ml of promethzine, and then re-upping with 15 ml twice during the trip. The following photos were taken from the #sizzurp Instagram tag.
"00:00 - Two large serving spoons, roughly 20ml."
"00:30 - After about a half hour or so I felt my innards go numb. I was hoping for a euphoric state, but did not feel one."
"1:00 - ...I noticed a strange sensation in my nerves, however. It seemed that I was easily startled. My nerves would jolt at unexpected noises or movements."
"2:00 - ...There was also mild head high, and I was still easily startled."
"02:30 - I was really sleepy, so I decided to lay in my bed. I dozed off almost instantly."
Most of the other Erowid trip reports describe very similar effects:
• Waves of nausea
• Constricted pupils
• Intense drowsiness
• Droopy eyes
• Slurred speech
• Mild euphoria
• Occasional, though rare, visual hallucinations, mainly consisting of flashing lights or colors
• Inner numbness
"In all the experience wasn't enjoyable. It wasn't terrifying though either. I'd probably never do it again, simply because it didn't really produce any favorable effects. Hydrocodone cough syrup is a million times better."
As for why promethazine causes seizures, one of its rare known side effects is a lowering of a user's seizure threshold.
Because of promethazine's dangerous side effects, in many countries it's illegal to prescribe to children and the elderly:
Since its approval in 1951, serious and often life-threatening adverse events, including respiratory depression, oversedation, agitation, hallucinations, seizures, and dystonic reactions, have been reported with promethazine use in children.