Short communicationPrevalence and recognition of highly significant medication-smoking cessation interactions in a smoke-free hospital
Introduction
One in six people admitted to hospitals are smokers (Szatkowski et al., 2015). Increasingly, hospitals are becoming smoke-free environments. Tobacco smoke interacts with medications via several mechanisms, including induction of cytochrome-P450 enzymes, particularly CYP1A2, activation of the sympathetic nervous system, reduction in blood flow to the skin, and up-regulation of alpha-1-acid glycoprotein production (Zevin and Benowitz, 1999). Whilst many potential interactions are of minimal clinical significance, medications recognized to have most clinically relevant interactions with tobacco smoke are clozapine, olanzapine and theophylline (UK Medicines Information, 2012). As patients stabilized on these specific medications move into a smoke-free environment, health professionals need to consider the impact of changes in smoking habits on therapy and potential adverse events.
Tobacco smoke induction of CYP1A2 increases metabolism of clozapine, olanzapine and theophylline; several case studies have reported increased plasma concentrations due to smoking cessation resulting in seizures, extrapyramidal effects and tachycardia, respectively (Lowe and Ackman, 2010; Rao, 1996). Providing nicotine replacement therapy does not affect nor prevent these interactions, as this therapy does not impact CYP1A2 enzyme activity.
Smoking cessation can produce a reduction in CYP1A2 activity of 20% by day two and 36% by day seven (Faber and Fuhr, 2004). Therefore, patients admitted for a short stay who alter their smoking habits briefly may have reduced potential for clinically significant interactions. On the other hand, if the patient stay exceeds one to two days, there is the risk that it may lead to serious adverse events if the interaction is not identified and addressed at the time of admission. Medication-smoking cessation interactions may be less important when these medications are initiated on hospital admission, as clinicians titrate doses to clinical effect. If patients resume smoking after leaving hospital, clinicians need to consider follow-up monitoring and titration of these medications.
Potential interactions may go unrecognized for several reasons. Documentation of smoking status in medical records remains suboptimal in many hospitals (Schofield and Hill, 1999; Smith et al., 2013). Anecdotally, there is limited awareness of the impact of smoking cessation on medications. In hospitals with electronic prescribing, documentation of smoking status and prescribing may not be linked.
Despite the clinical relevance of some medication-smoking cessation interactions, the prevalence of patients at risk for such interactions in smoke-free hospitals has not been documented. The objectives of this study were to determine the period prevalence of patients at risk of potentially highly significant medication-smoking cessation interactions in a smoke-free hospital, characterize those patients, and evaluate health professionals’ recognition of such interactions.
Section snippets
Methods
A retrospective cross-sectional study was conducted at Austin Hospital, Melbourne, Australia, a 400-bed tertiary-referral public hospital with approximately 33,000 non-same-day admissions and 82,000 emergency department visits in 2015. Austin Health implemented a smoke-free policy in 2009 and has undertaken broad implementation of an electronic medicines management system, Cerner Millennium (Cerner Corporation, Kansas City, MO).
Adult patients were included if they were prescribed clozapine,
Results
Olanzapine, clozapine or theophylline were prescribed during 1341 adult admissions in 2015, as detailed in Fig. 1. The period prevalence of patients at risk of a highly significant medication-smoking cessation interaction when prescribed clozapine, olanzapine or theophylline was 23/48 (48%), 66/256 (26%) and 1/16 (6%), respectively. As outlined in Table 1, one-third of admissions of smokers prescribed clozapine were for one or two days, but another one-third were for eight or more days. Over
Discussion
To our knowledge, this is the first study to investigate the period prevalence of patients at risk of potentially highly significant smoking-medication interactions in a smoke-free hospital setting. The clozapine and olanzapine groups had the greatest prevalence of risk of potential interactions. Given the high prevalence of smoking in patients with schizophrenia and that clozapine is prescribed for patients resistant to or unable to tolerate other medications, the high prevalence of
Conclusions
In conclusion, this study found that clinically important potential medication-smoking cessation interactions are prevalent in a smoke-free hospital but are frequently overlooked by health professionals. Awareness of clinically important medication-smoking cessation interactions among clinicians and alerts regarding potential interactions may prevent adverse effects.
Role of funding source
Nothing declared.
Contributors
ST and JG designed the study. CC collected data. Analyses were performed by ST and CC. ST and CC led the drafting of the manuscript. JG and DT revised the manuscript. All authors have contributed to and have approved the final manuscript.
Conflict of interest
ST and JG have held an investigator-initiated research (IIR) grant from Pfizer focusing on hospital pharmacist-initiated smoking cessation interventions for hospitalized smokers. JG holds an IIR grant from Boehringer-Ingelheim. No other disclosures are reported.
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