Dose - Help pinning down Dosage?

[Cerebro]

SWIM has recently found a bottle of Acetaminophen and Codeine elixir, liquid, not pill form. It contains 120 mg of Acetaminophen and 15 mg of Codeine per 5 ml. SWIM doesn't know of anyway to separate the Acetaminophen from the codeine in liquid form, all the CWE instructions are always about pills. SWIM is new to codeine. SWIM tried a tiny bit last night, 1 and a half teaspoons, about 7 and a half ml, so maybe 22.5 mg of codeine, and 180 mg of Acetaminophen. This did not do much for SWIM, and was a bit disappointed in that. But he expected that anyway. How much can SWIM safely take in one go that actually has some recreational potential to it, without SWIM destroying his liver? SWIM is 120 pounds, or 54 kg.