Plasma and cerebrospinal fluid pharmacokinetic parameters after single-dose administration of intravenous, oral, or rectal acetaminophen.

Background: This is the first study to compare plasma and cerebrospinal fluid (CSF) pharmacokinetics of intravenous (IV), oral (PO), or rectal (PR) formulations of acetaminophen.

Methods: Healthy male subjects (N = 6) were randomized to receive a single dose of IV (OFIRMEV(®) ; Cadence) 1,000 mg (15 minute infusion), PO (2 Tylenol(®) 500 mg caplets; McNeil Consumer Healthcare), or PR acetaminophen (2 Feverall(®) 650 mg suppositories; Actavis) with a 1-day washout period between doses. The 1,300 mg PR concentrations were standardized to 1,000 mg.