Determination of Cotinine, 3′-Hydroxycotinine, and Their Glucuronides in Urine by Ultra-high Performance Liquid Chromatography

Application of an assay for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in urine for the assessment of tobacco-related harm

BACKGROUND

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is formed from nicotine and related compounds during tobacco curing and is classified as a human carcinogen. Its major metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), is thought to be useful in the assessment of cigarette smoking harm minimisation strategies.

METHODOLOGY

Urine samples were collected from 24 current Caucasian smokers participating in a smoking cessation study; before and four weeks after a quit attempt. Samples were spiked with NNAL-d3 internal standard, extracted with ethyl acetate using liquid-liquid extraction, reconstituted with deionised water and analysed using ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS). Both free (unconjugated) and total NNAL was measured, with totals determined by cleavage of NNAL-glucuronide using standard enzymatic hydrolysis methods.

RESULTS

Free NNAL levels (193.5±158.2pg/mL [mean±standard deviation]) measured in urine samples obtained at baseline (during ad lib smoking) were indicative of biological exposure to NNK. Free NNAL levels were significantly reduced four weeks after the quit attempt (64.5±77.6pg/mL; p<0.002). Assay performance met acceptance criteria with mean recovery of 59±23%, intra-day accuracy was 3.7%, 3.7 and 3.6% and precision was 11.3%, 5.1% and 5.3% at 5pg/mL, 20pg/mL and 100pg/mL levels respectively. Enzymatic hydrolysis of NNAL-glucuronide proved unreliable with complete loss of NNAL aglycone in some subject samples following the hydrolysis procedure.

CONCLUSION

Liquid-liquid extraction with UPLC-MS/MS is a convenient approach to measure low levels of NNAL in urine as a marker of biological NNK exposure, which can be used to assess the effectiveness of smoking reduction harm minimisation strategies. Enzymatic hydrolysis of NNAL-glucuronide and measuring the aglycone is not recommended.

Examination of the mechanism of action of two pre-quit pharmacotherapies for smoking cessation

Background

There is substantial scope for improvement in the current arsenal of smoking cessation methods and techniques: even when front-line cessation treatments are utilized, smokers are still more likely to fail than to succeed. Studies testing the incremental benefit of using nicotine patch for 1–4 weeks prior to quitting have shown pre-quit nicotine patch use produces a robust incremental improvement over standard post-quit patch treatment. The primary objective of the current study is to test the mechanism of action of two pre-quit smoking cessation medications—varenicline and nicotine patch—in order to learn how best to optimize these pre-quit treatments.

Methods/Design

The study is a three group, randomized, open-label controlled clinical trial. Participants (n = 216 interested quitters) will be randomized to receive standard patch treatment (10 weeks of patch starting from a designated quit day), pre-quit patch treatment (two weeks of patch treatment prior to a quit day, followed by 10 weeks post-quit treatment) or varenicline (starting two weeks prior to quit day followed by 10 weeks post-quit). Participants will use study-specific modified smart-phones to monitor their smoking, withdrawal symptoms, craving, mood and social situations in near real-time over four weeks; two weeks prior to an assigned quit date and two weeks after this date. Smoking and abstinence will be assessed at regular study visits and biochemically verified.

Discussion

Understanding how nicotine patches and varenicline influence abstinence may allow for better tailoring of these treatments to individual smokers.

Trial registration

Australian New Zealand Clinical Trials Registry, ACTRN12614000329662 (Registered: 27 March 2014).