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Effect of passive smoking on theophylline clearance in children
1University of Alberta Hospital, Edmonton, Alberta, Canada. pmayo@cha.ab.ca
Insights
Passive tobacco smoke exposure significantly increases theophylline clearance in children with asthma. This leads to lower drug levels and longer hospital stays for asthmatic children exposed to secondhand smoke.
Area of Science:
- Pharmacology
- Environmental Health
- Pediatrics
Background:
- Asthma exacerbations in children require effective management, often involving theophylline.
- Environmental tobacco smoke exposure is a known risk factor for respiratory illnesses in children.
- The impact of passive smoking on drug metabolism in pediatric asthma patients is not well understood.
Purpose of the Study:
- To investigate the effect of passive tobacco smoke exposure on theophylline metabolism in pediatric asthma patients.
- To compare theophylline clearance and serum levels between asthmatic children exposed and unexposed to environmental tobacco smoke.
- To assess the correlation between passive smoke exposure, drug levels, and clinical outcomes like hospital stay duration.
Main Methods:
- Retrospective analysis of 201 pediatric asthma patients with acute exacerbations.
- Identification of 31 children with confirmed environmental tobacco smoke exposure (parents smoked ≥1 pack/day).
- Age- and gender-matched control group without passive smoke exposure; both groups received intravenous aminophylline for ≥48 hours.
Main Results:
- Theophylline total body clearance was significantly higher in the passive smoking group (1.36 mL/min/kg) compared to the control group (0.90 mL/min/kg).
- Steady-state serum theophylline levels were significantly lower in children exposed to passive smoke (55.3 mg/L) versus unexposed children (73.2 mg/L).
- The length of hospital stay was significantly longer for children exposed to passive smoke (4.4 days) compared to the control group (2.9 days).
Conclusions:
- Passive tobacco smoke exposure significantly increases theophylline clearance in pediatric asthma patients.
- Elevated theophylline clearance in exposed children leads to lower serum drug concentrations.
- Findings suggest passive smoking may alter the metabolism of other drugs cleared similarly to theophylline, impacting treatment efficacy and patient outcomes.
Abstract:
The author investigated the effects of passive tobacco smoking on the metabolism of theophylline in a pediatric population. In a retrospective analysis of 201 children admitted to a pediatric unit for asthma, 31 were identified with an acute exacerbation of asthma of noninfectious origin in which environmental exposure to tobacco smoke could be established. The parents were known smokers with a minimum 1-pack-per-day habit. An age-and gender-matched control population of children was then identified who had an acute exacerbation of asthma without any environmental exposure to tobacco smoke. In addition, the patients in both groups received the same dose of intravenous aminophylline for a minimum of 48 hours to ensure steady-state conditions. Total body clearance of theophylline was significantly elevated in the children exposed to environmental tobacco smoke (1.36 +/- 0.09 vs. 0.90 +/- 0.04 mL/min per kg, p < 0.0001). Steady-state serum levels were significantly lower in the passive smoking group (55.3 +/- 2.8 vs. 73.2 +/- 3.3 p < 0.00001) for those receiving nearly identical intravenous doses. The length of hospital stay was longer in the group exposed to passive smoke (4.4 +/- 2.6 vs. 2.9 +/- 1.3 days, p < 0.05). The clearance of theophylline is greater in asthmatic children exposed to passive tobacco smoke than in asthmatic children not exposed to passive tobacco smoke. These findings suggest that passive smoking may increase the clearance of other drugs metabolized in a manner similar to theophylline.