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After controlled oral administration of D,L-methadone solution (15-260 mg/day) in the context of a methadone-maintenance program, concentrations of methadone and 2-ethylidine-1,5-dimethyl-3,3-diphenyl-l-pyrrolidine (EDDP), in head hair were determined (N=41), using a fully automated headspace solid-phase microextraction procedure in combination with gas chromatography and mass spectrometry (HS-SPME/GC/MS).Methadone was present in all samples in concentrations ranging from 0.25 to 13.29 ng/mg (mean 2.69±0.45 ng/mg). EDDP was also present in every sample in concentrations ranging from 0.05 to 2.17 ng/mg (mean 0.43±0.08). The concentration ratio methadone/EDDP was 7.5±5.7 in the proximal segments, but decreased to 4.8±1.4 in the distal segments. A statistically significant correlation between the intake dose and the methadone and EDDP concentrations in the subjects' hair could be established only in the proximal segments (r=0.913 for methadone and r=0.901 for EDDP), but not in the distal segments. In all, 131 segments analyzed, the correlation coefficient was r=0.760 for methadone and r=0.738 for EDDP. In comparison to the dose-concentration relationship reported in the literature, we found a better correlation with higher correlation coefficients especially in the proximal segments.However, owing to a broad distribution in the correlation between dosage and concentration, the determination of methadone and EDDP in hair holds only limited information about prior methadone administration.

Epidemiological studies indicate an increased risk of esophageal cancer from the consumption of very hot foods and beverages. The contact time and the contact temperature are decisive for the risk of injury. However, measuring the contact temperature is not easy in practice. In the present study, a numerical simulation based on the solution of the heat conduction equation was initially used to investigate whether and for what period of time a constant contact temperature is to be expected under oral conditions. For small food samples (e.g., cooked potatoes) in contact with the tongue, the simulation results in constant contact temperatures of up to 10 s before cooling depending on thickness. Hot beverages, which spread as a thin film and thereby increase their surface area, can therefore be consumed at higher temperatures than solid foods. Furthermore, orientating measurements with a “measuring spoon” determined the contact temperature of 46.5 °C considered to be just comfortable for any period >10 s and about 48 °C for periods of less than 10 s The course of the contact temperatures determined in the experiment over time allows the corresponding threshold values of consumption temperatures for various hot foods to be calculated. In view of the fact that the contact temperature is obviously the determining factor for the risk of injury from burns in the oral cavity in addition to the contact time, it makes sense to reference threshold values to the contact temperature rather than to the surface or consumption temperature of a food product, which is current customary practice. If this contact temperature is defined as a threshold value, the surface or consumption temperature for any other food can be calculated.