Smoking modulates neuroendocrine responses to ipsapirone in patients with panic disorder

Reduced 5-HT1A-receptor responsiveness has been reported in patients with panic disorder(PD) and/or agoraphobia (PDA). Although many of these patients are regular smokers, it has not been examined whether psychological or neurobiological effects induced by the selective 5-HT1A-receptor agonist, ipsapirone, are affected by the smoking status of the patients. In order to clarify this question neuroendocrine challenges with oral doses of ipsapirone (0.3 mg/kg) and placebo were performed in 39 patients with PDA, and results were compared between patients who smoked (>10 cigarettes per day, n = 17) and patients who had been non-smokers for at least two years (n = 22). Patients who were smokers (but did not smoke during the challenge procedure) had significantly reduced baseline concentrations of cortisol and a significantly lower body temperature. In comparison to placebo, administration of ipsapirone was associated with significant increases of various psychological symptoms and plasma cortisol concentrations. The subgroup of PD patients who were smokers showed significantly higher cortisol responses to ipsapirone than non-smokers. In conclusion, smoking status has to be taken into account when assessing the responsiveness of 5-HT1A receptors in patients with psychiatric disorders. The prevention of smoking during challenge sessions might not be the ideal approach in heavy smokers, since sudden abstinence from smoking is likely to affect neurobiological and possibly psychological responses to ipsapirone.