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1.
Prescription narcotic cough syrups. Most contain Hydrocodone or Codeine. These syrups have other ingredients in them for treating cold and cough symptoms, such as Antihistamines or Decongestants.

Some Common Formulas:
Tussionex- 10mg Hydrocodone (Extended-Release) and Chlorpheniramine 8mg per 5ml (1 tsp.)
Codiclear/Hycotuss- Hydrocodone and Guaifenesin
Lortab Elixir- Hydrocodone and Acetaminophen
Prometh VC with Codeine: Codeine and Promethazine

Often people will add Alcohol, Flavorings (ex. Kool-Aid), or crushed-up pills (such as Vicodin) to potentiate the effects of the syrup or make it taste better.

A somewhat common misperception is that Sizurp refers to over-the-counter cough syrups containing DXM (dextromethorphan) which some abuse ("Robotrippin") for its dissassociative effects.
From Three Six Mafia, Sippin on Some Sizzurp:

"I got the wet promethazine, thick orange & yellow tuss
Hydroco-done...Sippin on Some Sizurp..."
by WSB15 February 21, 2006
 
2.
n.
1. An illegal effervescent cocktail beverage consumed by hoods.
a. Recipe: One part strawberry soda (8oz), one part cough syrup (Dextromethorphan HBr), one teaspoon crushed codeine. Shake mixture well; drink cold.

b. Recipe (optional): One part cough syrup (Dextromethorphan HBr), one part ginger ale soda.
by Matt Hoyt February 10, 2004
 
3.
sizurp-prescription cough syrup, usually tussionex(10mg of hydrocodone/teaspoon)mixed with nyquil and cool-aid.
how much for that sizurp?
$40 for just one ounce!!
by j. saint.r October 17, 2003
 
4.
a mix of codeine and cough syrup served martini style with alcohol
36 MAFIA, crush codeine and mix with strong cough syrup, then add to shaker with somerhing like gin and juice
by wej johnson March 15, 2003
 
5.
sizurp is the reference to prescription cough syrup containing hydrocodone and/or promethizine
tussionex, pancof
by j. saint.r October 17, 2003