To add to our understanding of the relationship between blushing, symptom severity and potential mechanisms that underlie blushing in patients with SP, we propose comparing SP patients' vascular responses to topical m-N pre and post treatment with S-citalopram or placebo.

S-citalopram (an SSRI) has been widely used in the treatment of mood and anxiety disorders as it has shown efficacy in these patients (Lepola et al., 2003; Stahl et al., 2003; Burke et al., 2002; Davidson et al., 2002; Wade et al., 2002). In comparison to placebo, S-citalopram has been shown to be effective and well tolerated in those with short and long term SP (Lader et al 2004; Montgomery et al., 2003; Kasper et al., 2002). As indicated, responses to the blushing exposure will be assessed prior to and following treatment with S-citalopram or placebo and at one month following the intervention.

Levels of prostaglandin will be compared between groups and will also be correlated with symptom severity in the clinical groups. Effective psychological interventions that reduced the fear of blushing in individuals with social phobia did not lead to a reduction in actual blushing during a social test (Mulkens et al., 2001). As such, it is expected that the patients' perception of amount of blushing will change following treatment. In addition, we are undertaking an investigation as to whether nican topical administration will change following treatment to match the pattern seen in healthy controls.

The objectives are to evaluate the efficacy of S-citalopram 10 to 20 mg once daily (QD) in the treatment of social phobia and to determine if treatment outcome is related changes in intensity of the vasodilatory response to 10 mM topical m-N. This is a randomized, double-blind flexible-dose study evaluating the efficacy, safety and tolerability of S-citalopram 10 to 20 mg and placebo in outpatient subjects diagnosed with SP. At the screening visit those who are eligible will enter a randomized trial with S-citalopram 10 to 20 mg and placebo. The study will begin with a single week of S-citalopram 10 mg. Subsequently, capsules will be administered in a flexible dose fashion and patients will be followed up weekly (biweekly after week 6) and at the clinician's discretion. After the first week the patients' dosage will be increased up to a maximum of 20 mg daily. This dose will remain fixed after 8 weeks of treatment until week 16.