In this randomized blinded study, SJW did not significantly increase tobacco abstinence rates or decrease nicotine withdrawal compared to placebo. Study dropout was high, but no differences in abstinence rates were observed among subjects reporting use of ≥75% of their assigned doses. SJW was well tolerated in a dose up to 1800
mg per day.
Previous studies have reported conflicting results with respect to the efficacy of SJW for increasing smoking abstinence. In a blinded, placebo-controlled study using SJW at 900
mg/day, 6/71 (8.5%) participants on SJW and 9/72 (12.5%) on placebo achieved prolonged smoking abstinence at 4 weeks [odds ratio (OR)
0.65; 95% confidence interval (CI): 0.22–1.92]. At 6 months, 3 (4.2%) of subjects in the SJW group and 6 (8.3%) subjects on placebo were abstinent from smoking [OR
0.49; 95% CI: 0.12–2.02)]. No effect on tobacco withdrawal symptoms was observed.27
In another study among 28 smokers who received SJW herb extract either 300
mg once a day or 300
mg twice daily taken for 1 week before and continued for 3 months after a TQD, the point prevalence and continuous smoking abstinence rate were both 18% at 3 months.28
Fifteen (15) participants (54%) reported adverse events, mainly gastrointestinal. This study concluded that SJW plus individual behavioral support was unlikely to be an effective aid for smoking cessation.
However, some investigations have observed a beneficial effect of SJW for increasing smoking abstinence rates. In an open-label study with 37 cigarette smokers who received 900
mg/day of SJW for 3 months, the point prevalence of smoking cessation rate at 3 months was 24% (9/37).9
Despite the small sample size, this abstinence rate was higher than the expected rate with placebo or no pharmacologic aids (approximately 15%).29,30
In the present study, we did observe a decrease in nicotine withdrawal and craving; however, there was no evidence of a difference across treatment groups.
Several possible hypotheses can be proposed as to why SJW did not demonstrate benefit for increasing smoking abstinence rates in our study. First, SJW may lack efficacy for tobacco abstinence. A review of the other pilot studies published with SJW suggests this to be the most plausible conclusion. Second, since we used an intention-to-treat analysis and had a high dropout rate, our study may have been underpowered to detect an effect. Our study was powered at 82% to detect an end-of-treatment abstinence rate of 40% or greater for an active SJW group compared to placebo (using a one-sided, α
0.05 level test) with a sample size per group of 40. With the significant attrition, conceivably a smaller effect may have been missed. Third, considerable variation exists in the available SJW preparations. Prior studies with SJW for smoking cessation contained differing amounts of the active ingredient.9,28
The present study used a dose of SJW with 0.3% hypericin. Different concentrations of the medication across different studies may influence the efficacy.
The major limitation of this study was a high dropout rate of 43%. The exact reasons for this are unclear. This observed dropout rate was higher than what has been observed in previous trials. A possible explanation may include a significant patient burden with taking numerous pills. SJW was only available in 300
mg and 600
mg formulations, and our study involved taking one tablet 3 times a day for 12 weeks, which could have adversely affected treatment adherence. SJW can also be obtained relatively inexpensively over the counter ($15 per month's supply), which raises the possibility that subjects who found it helpful may have obtained it themselves to avoid the burden of study participation. Finally, the high dropout may relate to the fact that study participants did not find any effect from SJW and discontinued use of the product. The low adherence rate to SJW suggests that, even if SJW were efficacious, low uptake rate in the clinical setting would translate into an ineffective intervention.
In summary, we observed that SJW did not increase smoking abstinence rates and did not decrease tobacco withdrawal symptoms. The dropout rate in our study was high. Given the lack of efficacy in several pilot studies, further testing of SJW for tobacco cessation may not be warranted.