Rationale  

Hypericum perforatum is used as a natural antidepressant, and other antidepressants have been marketed to aid in smoking cessation.

Objective  

We investigated the effects of an extract of Hypericum perforatum (Ph-50) on withdrawal signs produced by nicotine abstinence in mice.

Methods  

Nicotine (2 mg/kg, four injections daily) was administered for 14 days to mice. Different doses of Ph-50 (125–500 mg/kg) were administered orally immediately after the last nicotine injection. In another experiment, Ph-50 (500 mg/kg) was orally administered in combination with nicotine, i) starting from day 8 until the end of the nicotine treatment period, or ii) during nicotine treatment and after nicotine withdrawal, or iii) immediately after the last nicotine injection. On withdrawal from nicotine, all animals were evaluated for locomotor activity and abstinence signs.

Results  

The locomotor activity reduction induced by nicotine withdrawal was abolished by Ph-50, which also significantly and dose-dependently reduced the total nicotine abstinence score when injected after nicotine withdrawal.

Conclusions  

These data show that treatment with Hypericum perforatum attenuates nicotine withdrawal signs in mice. Further studies are necessary to test the possibility that it may be used for smoking cessation treatment in humans.