Cigarette smoking prevalence is extremely high, and cessation rates are very low among heroin addicted subjects in opioid substitution therapy. There is a large body of anecdotal evidence about the association between drug addiction and tobacco smoking, yet despite the amount of literature that has been published on this issue, the state of research on tobacco smoking among the subjects in methadone treatment is not as developed as it should be (and even less so in buprenorphine treatment). There is however the clear need to better understand the relationship between opioids use and cigarette consumption.
Most common key findings about methadone clients are a high prevalence of smoking, generally more than 80%, and a very low quitting rate, generally less than 10%. Common, in most studies, is the statement that the best medicine for nicotine treatment in methadone and buprenorphine-maintained subjects is far from adequate and the need of tailored interventions for this population [1
Placebo controlled studies confirmed that addictive drugs use or abuse may be associated to an increased nicotine intake. For instance, ethanol administration in alcoholics [5
] and in non-alcoholic social drinkers [6
] increased tobacco smoking. Administration of D-amphetamine increased smoking behaviour in non-drug abuser smokers, similarly to pentobarbital in ex-drug abuser smokers [7
]. Among the substances that have been suggested to potentiate nicotine intake, heroin and methadone are of particular interest because of their potential reciprocal effect, respectively as drug of abuse and substitution drug therapy. Heroin addicted smokers (HAS) smoked more cigarettes when heroin self-administration was allowed than during heroin-free or under methadone detoxification condition periods [8
]. Treatment for smoking cessation in this segment of smokers showed low success rates [9
]. It appears that it is more difficult for these individuals to quit smoking than heroin [11
It is reported that a high percentage of methadone-maintained patients are tobacco smokers. The number of daily smoked cigarettes gradually decreases along with daily methadone maintenance dose during a progressive methadone dose reduction period [12
]. Chait and Griffiths showed that methadone induced a dose-related increase of smoking [13
]. Methadone and nicotine have been shown to decrease restlessness, irritability, and depression [14
]. Methadone has been shown to influence timing and smoking rate in a dose dependent correlation [15
]. Cigarette smoking rates are higher in the methadone-maintained opiate-dependent people than in the general population [16
]. At least 80% of methadone patients smoke [2
]. Similarly, opioid substitution therapy with buprenorphine showed increased smoking rates [19
]. Recently, it was reported that methadone and nicotine interaction in methadone-maintained patients enhances ratings of euphoria and drug liking [4
The relationship between the type and dosage of opioid substitution therapy and smoking status, as well as the potential role of other biological and psychosocial variables such as gender, age, psychiatric co-morbidities, etc
., is currently unclear. Some studies have implicated methadone as a determinant factor, e.g., increasing methadone dose increases smoking [11
]. The methadone/nicotine interaction is very complex [21
], further complicated by habituation seen at higher methadone doses [1
]. Despite this body of literature describing the associations between methadone, buprenorphine, and nicotine, it should be noted that most of these experimental studies have been performed in research laboratories and with limited follow-up. One thing is to observe the correlates of smoking in a laboratory, and quite another is to observe smoking habit in daily living environment.
Therefore, more data are needed on the methadone/nicotine interaction in order to possibly revise dose regimen and protocols for methadone substitution therapy, or for other opioid substitution therapy such as that with buprenorphine.