The drugs have been tested primarily on heavy smokers.
In general, clinical trials on drugs that help people quit smoking have been conducted on heavy smokers. That makes sense, because this is the group that needs the most help.
However, because of the emphasis on the group with the toughest habit to break, there are few guidelines on how light smokers should use the drugs or whether the drugs are effective in helping light smokers quit. The research does show, however, that even light smoking has adverse effects on health.
A recent study examined the habits of smokers from racial and ethnic minorities, and found that while they were more likely to be light smokers, they had just as little success quitting as other smokers and were less likely to receive medical intervention in quitting [source: Claremont Graduate University].