No abstract

To verify the assumptions in our previous risk assessment of an atropine/scopolamine mixture in buckwheat flour, we performed a randomized, double-blind, placebo-controlled cross-over study in 20 healthy, adult volunteers. The volunteers ingested a traditional Slovenian buckwheat meal, made of boiled buckwheat flour to which alkaloids were added. In addition to the placebo they ingested 0.12/0.10, 0.37/0.29, 1.22/0.95, 3.58/2.81 and 12.10/9.50 µg kg(-1) body mass (BM) of the atropine/scopolamine mixture. The changes in body temperature, heart rate, salivary and sweat secretion, pupil size, near-point vision and subjective symptoms were recorded regularly for 4 h after the ingestion. Decreased salivary and sweat secretion, increased heart rate and pupil size and reduced near-point vision accompanied by characteristic subjective symptoms were observed at 12.10/9.50 µg kg(-1) BM. At doses of 0.37/0.29 and 1.22/0.95 µg kg(-1) BM, a significant decrease in the heart rate was noted, which we consider to be a critical effect of a low-dose exposure to the atropine/scopolamine mixture. Although this did not have any clinical relevance in our subjects, it may have serious implications if it occurred in people with pre-existent cardiac conditions or those on medications that may cause bradycardia. No significant changes in the observed end points were noted at 0.12/0.10 µg kg(-1) BM. We estimate that the NOAEL (No Observed Adverse Effect Level) for the atropine/scopolamine mixture lies between the lower two administered doses. Applying the uncertainty factor of 10, we propose a new provisional Acute Reference Doses (ARfDs) of the mixture, i.e. 0.01 µg kg(-1) BM for each alkaloid, and a further refinement using higher-tier approaches.

In Slovenia, a mass poisoning incident involving 73 consumers with symptoms such as dry mouth, hot red skin, blurred vision, tachycardia, urinary retention, ataxia, speech disturbance, disorientation and visual hallucinations occurred in 2003. In all cases, consumers had eaten buckwheat flour food products within the last few hours. Investigations by responsible authorities identified the contamination of a range of buckwheat food products with thorn-apple (Datura stramonium L.) seeds containing toxic alkaloids, atropine and scopolamine. To ensure the safe consumption of buckwheat food products, we carried out risk characterisation and proposed provisional maximum residue levels (MRLs) of atropine and scopolamine mixture in buckwheat flour. In the absence of critical "no observed adverse effect levels" for atropine and scopolamine, we based our estimation of the acute reference doses on the lowest recommended therapeutic doses. Taking into account the additive effect of the two alkaloids, we calculated acute reference doses of the mixture, that is 0.05 µg/kg of body mass for atropine and 0.03 µg/kg of body mass for scopolamine. MRLs for atropine and scopolamine mixture in buckwheat flour were estimated in a worst-case scenario, that is consumption of 100 g of flour by a child weighing 10 kg and taking into account a range of atropine/scopolamine ratio in implicated food products, that is 0.85-3.3. We proposed the national MRLs for atropine/scopolamine mixture in buckwheat food products: 4.0 µg/kg (atropine) and 2.0 µg/kg(scopolamine). However, in view of the large variability in the alkaloid content, depending on the origin of the Datura, we propose that risk assessment should be carried out on a case-by-case basis, taking into account the ratio between atropine and scopolamine content in a particular sample.

No abstract

The aim of the present work was to establish whether the secretory process can be influenced by histamine H2-receptor antagonists, burimamide and metiamide. These drugs were applied intravenously and the secretion was evoked by the electrical stimulation of the chorda tympani nerve or by carbachol (i.v.). In addition to the measurements of the flow of saliva, the blood flow through the gland was measured in some experiments. Both H2-antagonists significantly reduced the rate of salivary secretion induced by the chorda tympani stimulation. The experiments with burimamide did not permit the calculation of dose-response relationship. From the experiments with metiamide the ED50 was 4.6 mumols/kg and Emax was 30% reduction of secretion. The secretory response to carbachol was not diminished by burimamide. In addition to the effect of metiamide on salivation, the reduction of the blood flow through the gland was observed: the effect on the blood flow was significantly smaller, and slower in onset, than the effect on salivation. These results support the hypothesis that H2-receptors are involved in the process of salivary secretion. Histamine effects on glandular elements seem to be more significant than its effect on the blood vessels.