Pharmacokinetics of nicotine tartrate after single-dose liquid enema, oral, and intravenous administration
Ulcerative colitis is predominantly a disease of nonsmokers, and transdermal nicotine is therapeutic but often results in adverse reactions. Colonic administration of nicotine tartrate as a liquid enema could decrease systemic nicotine absorption and adverse reactions. The purpose of the current study was to determine the bioavailability and pharmacokinetic parameters of nicotine after administration by hydrophilic liquid enema (acidic and basic), hydrophobic liquid enema (acidic and basic), and by oral and intravenous routes. Thirty healthy volunteers received 45 micrograms nicotine base/kg (as nicotine tartrate) in one of five formulations (each n = 6): hydrophilic acidic liquid enema, hydrophilic basic liquid enema, hydrophobic acidic liquid enema, hydrophobic basic liquid enema, and oral solution. All participants also received 15 micrograms nicotine base/kg (as nicotine tartrate) intravenously during a separate study period. Serum concentrations of nicotine were determined by gas chromatography with mass spectrometry. The mean (+/-SD) bioavailabilities of nicotine after administration in the liquid enema formulations (hydrophilic acidic 17 +/- 18%, hydrophilic basic 16 +/- 16%, hydrophobic acidic 25 +/- 17%, hydrophobic basic 15 +/- 12%) were similar to the bioavailability of nicotine after administration by oral solution (20 +/- 25%). The bioavailabilities of nicotine for all five nonintravenous formulations were significantly less than for intravenous nicotine (100%). Serum concentrations of nicotine did not predict adverse reactions. Nicotine tartrate administered as either a liquid enema or as an oral solution had low bioavailability and was well tolerated. The therapeutic potential of nicotine tartrate liquid enemas, which can potentially limit toxicity by local (colonic) delivery of high doses of nicotine should be investigated in patients with left-sided ulcerative colitis.