Introduction Smoking is the largest preventable cause of death and related disease in the United Kingdom. Smoking-related diseases account for around 15 to 20 per cent of all deaths in Britain, of which around 25 per cent occur in people aged under 65 years. Pharmacists have a key role to play in smoking cessation, not only by supplying and recommending appropriate smoking cessation products, but also by providing support, advice and counselling to smokers.1

Nicotine replacement therapy (NRT) is efficacious in smoking cessation in over-the-counter settings, although overall quit rates are low (10 to 20 per cent). NRT has also been reported to increase six-month quit rates by a factor of approximately 1.5 to 2 over placebo, regardless of the setting.2

Nicotine may act as an antidepressant in some smokers and the development of a depressed mood or depression after smoking cessation may lead to relapse. These effects may be related to changes in dopaminergic activity in the brain. Consequently, antidepressant agents have been investigated as possible aids to smoking cessation either alone or in addition to NRT; bupropion is now licensed in the US for this indication. St John's wort (SJW; Hypericum perforatum) is efficacious in relieving the symptoms of mild-to-moderate depression,3 and recent work has suggested that effects on dopaminergic systems may be important for the herb's neurological activity.4

To date, SJW has not been investigated as an aid in smoking cessation, although there have been anecdotal reports of its use in nicotine withdrawal (personal communication). There may be a role for non-nicotine, non-prescription pharmacological aids in smoking cessation.

The aim of this study is to explore SJW as an aid in smoking cessation in order to develop a hypothesis for possible testing in a randomised clinical trial. Two dosages of St John's wort are being used to reflect different dosage regimens that are used across Europe. Method This is an open, uncontrolled study of a standardised extract of SJW and a programme of pharmacist-provided behavioural support, advice and counselling for smokers who wish to quit.

Smokers who meet inclusion and exclusion criteria are given a 30-minute appointment with a pharmacist at a pharmacy in North London which has consulting room facilities. Inclusion criteria include: age 18 to 65 years; motivation to quit smoking according to the "stage of change" model;5 smokers of at least 10 cigarettes daily for at least a year. Exclusion criteria include: those receiving regular prescription medicines; previous use of NRT or SJW within six months; pregnancy and lactation. Written informed consent is obtained before enrolment into the study.

Participants are randomised to receive tablets of a standardised extract of SJW 300mg each morning or 300mg twice daily for three months. Participants start taking SJW one week before a target quit date (TQD) and attend appointments with a pharmacist at one, three, six and 12 months after their TQD.

At these follow-up appointments, pharmacists with Centre for Pharmacy Postgraduate Education training in smoking cessation provide behavioural support and counselling, record smoking behaviour since the previous visit, measure exhaled air carbon monoxide concentrations and, in a 10 per cent random sample of participants, collect saliva samples for analysis of cotinine concentrations.

As this is an uncontrolled study, no formal power calculation was performed. On the basis that quit rates with NRT in OTC settings are low (10 to 20 per cent),2 it is aimed to recruit 200 participants for the study.

Focal points Pharmacists have a key role to play in smoking cessation

St John's wort ( Hypericum perforatum ) is effective in mild-to-moderate depression; conventional antidepressant agents have been investigated as aids in smoking cessation

) is effective in mild-to-moderate depression; conventional antidepressant agents have been investigated as aids in smoking cessation An uncontrolled study of St John's wort together with a programme of pharmacist-provided behavioural support and advice is being carried out in motivated smokers

Participants are randomised to receive one of two doses of St John's wort for three months and are followed up for one year after stopping smoking

The primary outcome variables are the self-reported six-month smoking cessation rate and continuous abstinence verified biochemically