Toxicological assessment compilation of selected examples of raw materials for homeopathic and anthroposophic medicinal products - Part 2.

The present successor article comprises more than 180 substances representing a continuative compilation of toxicologically evaluated starting materials prompted by the wide use and high number of homeopathic and anthroposophic medicinal products (HMP) on the market together with the broad spectrum of active substances of botanical, mineral, chemical or animal origin contained therein, and by the equally important requirement of applying adequate safety principles as with conventional human medicinal products in line with the European regulatory framework. The February 2019 issue of the Regulatory Toxicology and Pharmacology journal includes the antecedent article bearing the same title and entailing safety evaluations of more than 170 raw materials processed in HMP. This part 2 article highlights scientific evaluation following recognized methods used in toxicology with a view to drug-regulatory authority's assessment principles and practice in the context of HMP, and offers useful systematic, scientifically substantiated and simultaneously pragmatic approaches in differentiated HMP risk assessment. As a unique feature, both articles provide the most extensive publicly available systematic compilation of a considerable number of substances processed in HMP as a transparent resource for applicants, pharmaceutical manufacturers, the scientific community and healthcare authorities to actively support regulatory decision making in practice.

Toxicological assessment compilation of selected examples of raw materials for homeopathic medicinal products.

The considerable number of homeopathic medicinal products (HMP) on the German market and the staggering breadth of active substances of various origin along with the specific legal requirements of adequate safety principles posed the need to compile data on toxicologically evaluated raw materials. In line with the European regulatory framework, HMP applications must consider appropriate safety standards in analogy to conventional human medicinal products. This review presents an option for a systematic and scientifically substantiated approach for regulatory use. Furthermore, this paper provides a multitude of data for selected raw materials processed in HMP with up to now rather scarce knowledge and, thus, aims at filling data gaps on acceptable amounts per day (AAD). The inclusion of raw materials into the compilation was determined considering the frequencies of their occurrence in HMP in Germany along with the availability of appropriate safety assessments. This safety evaluation compilation represents a practical, fairly comprehensive and systematic set of more than 170 raw materials. It is designed to both effectively support regulatory decision making and to be recognized and exploited by applicants, stakeholders and the scientific community.

Current concepts on integrative safety assessment of active substances of botanical, mineral or chemical origin in homeopathic medicinal products within the European regulatory framework.

For active substances of botanical, mineral or chemical origin processed in homeopathic medicinal products for human use, the adequate safety principles as with other human medicinal products are applied in line with the European regulatory framework. In homeopathy, nonclinical safety assessment is facing a particular challenge because of a multitude and diversity of source materials used and due to rarely available toxicological data. Thus, current concepts applied by the national regulatory authority in Germany (BfArM) on integrative safety assessment of raw materials used in homeopathic medicinal products involve several evaluation approaches like the use of the Lowest Human Recommended Dose (LHRD), toxicological limit values, Threshold of Toxicological Concern (TTC), data from food regulation or the consideration of unavoidable environmental or dietary background exposure. This publication is intended to further develop and clarify the practical use of these assessment routes by exemplary application on selected homeopathic preparations. In conclusion, the different approaches are considered a very useful scientific and simultaneously pragmatic procedure in differentiated risk assessment of homeopathic medicinal products. Overall, this paper aims to increase the visibility of the safety issues in homeopathy and to stimulate scientific discussion of worldwide existing regulatory concepts on homeopathic medicinal products.

Stimulation of hippocampal acetylcholine release by hyperforin, a constituent of St. John's Wort.

Extracts of the medicinal plant St. John's Wort (Hypericum perforatum) are widely used in the therapy of affective disorders and have been reported to exert antidepressant, anxiolytic, and cognitive effects in experimental and clinical studies. We here report that hyperforin, the major active constituent of the extract, increases the release of acetylcholine from rat hippocampus in vivo as determined by microdialysis. Hippocampal acetylcholine levels were increased by 50-100% following the systemic administration of pure hyperforin at doses of 1 and 10 mg/kg. The effect was almost completely suppressed by local perfusion with calcium-free buffer or with tetrodotoxin (1 microM). We conclude that hyperforin releases hippocampal acetylcholine by an indirect mechanism of action which is calcium-dependent and requires intact neuronal communication and cell firing. Our findings suggest therapeutic efficacy of St. John's Wort extracts in central cholinergic dysfunction.

Nitrergic modulation of hippocampal acetylcholine release is independent of endothelial NO synthase activity.

Nitric oxide (NO) is involved in hippocampal phenomena of synaptic plasticity. The present microdialysis study investigated a possible role of NO and of endothelial NO synthase (eNOS) activity in the control of hippocampal acetylcholine (ACh) release. 3-Morpholinosydnonimine (SIN-1), an NO donor, stimulated ACh release by 50%-70% when infused into the hippocampus of wild type C57B16 mice. Infusion of L-nitroarginine (L-NA), a broad-spectrum inhibitor of NO synthases, decreased hippocampal ACh efflux by approximately 50%. Mice lacking eNOS (eNOS knockouts) had identical basal effluxes of hippocampal ACh as wild type mice, and the responses to SIN-1 and L-NA were unchanged in the absence of eNOS activity. We conclude that nitric oxide (NO) stimulates hippocampal ACh release in a tonic fashion, but independently of eNOS activity.

NMDA-induced acetylcholine release in mouse striatum: role of NO synthase isoforms.

Striatal cholinergic interneurons are stimulated by glutamatergic inputs from thalamus and cortex via NMDA receptors. The present microdialysis study was designed to characterize the role of nitric oxide (NO) in this process and to identify the NO synthase (NOS) isoform responsible for this effect. For this purpose, we studied the effects of NMDA and 3-morpholino sydnonimine (SIN-1) perfusions on the release of acetylcholine (ACh) in mouse striatum. In wild-type C57/Bl6 mice, perfusion of NMDA (100 micro m) induced a two-fold stimulation of ACh release. This effect was attenuated in mice lacking endothelial NOS but was completely absent in mice lacking neuronal NOS. Local perfusion of SIN-1 (300 micro m), an NO donor, increased ACh release by more than two-fold in all three mouse lines. We conclude that NO synthesized by neuronal NOS provides a nitrergic link in the glutamatergic stimulation of striatal cholinergic interneurons.

Dual modulation of striatal acetylcholine release by hyperforin, a constituent of St. John's wort.

Extracts of the medicinal plant St. John's wort (Hypericum perforatum) are widely used for the treatment of mild to moderate depression. Hyperforin, a constituent of St. John's wort, is known to inhibit the sodium-dependent uptake of catecholamines and amino acids into synaptic nerve endings, probably by interference with mechanisms controlling the synaptic sodium concentration. Because de novo synthesis of acetylcholine (ACh) is dependent on sodium-dependent high-affinity choline uptake, we studied the effect of hyperforin on choline (Ch) uptake in vitro and on striatal ACh release in vivo using microdialysis. In rat brain synaptosomes, hyperforin inhibited high-affinity choline uptake with an IC(50) of 8.5 microM, whereas low-affinity uptake was not affected. Local infusion of hyperforin (100 microM) via the dialysis probe caused a delayed reduction of ACh release and a concomitant increase of Ch levels. Infusion of a lower concentration of hyperforin (10 microM), however, increased striatal ACh release and lowered Ch levels. Systemic administration of hyperforin (1-10 mg/kg i.p.) led to therapeutic plasma levels of hyperforin and caused a significant elevation of striatal ACh release. Behavioral testing revealed a reduction of locomotor activity in mice treated with high-dose (10 mg/kg) hyperforin. We conclude that low doses of hyperforin stimulate striatal ACh release by an unknown mechanism, whereas high doses inhibit synaptic choline uptake and ACh release. The results are discussed with respect to the therapeutic use of St. John's wort in patients with neurodegenerative disorders.