Plasma nicotine pharmacokinetics in dogs after intravenous administration: determination by radioimmunoassay.

Nicotine plasma levels in dogs were examined by radioimmunoassay after intravenous administration of S-nicotine at the dosage of 100 microgram/kg. After a rapid decline of nicotine level in plasma immediately following the injection, retention of the level was observed until 30 min. From that point the plasma level decreased monoexponentially. A biological half life (t 1/2, beta) of 0.61 hr we observed in dogs was similar to that in man and one half of that in rats. Total body clearance (TBC) and apparent volume of distribution (Vd, beta) in dogs were about 1/5 of that in rats. The results suggested that nicotine does not distribute in dogs as readily as in rats. Similarity in a biological half life of nicotine in dogs and humans suggested that the dog may be a better experimental model than the rate in the investigation of pharmacokinetic parameters for nicotine.