Absence of herb-drug interactions of mistletoe with the tamoxifen metabolite (E/Z)-endoxifen and cytochrome P450 3A4/5 and 2D6 in vitro.

BACKGROUND: Women diagnosed with breast cancer frequently seek complementary and alternative (CAM) treatment options that can help to cope with their disease and the side effects of conventional cancer therapy. Especially in Europe, breast cancer patients use herbal products containing mistletoe (Viscum album L.). The oldest and one of the most prescribed conventional drugs for the treatment of estrogen receptor positive breast cancer is tamoxifen. Aside from positive clinical experience with the combination of tamoxifen and mistletoe, little is known about possible herb-drug interactions (HDIs) between the two products. In the present in vitro study, we investigated the effect of standardized commercial mistletoe preparations on the activity of endoxifen, the major active metabolite of tamoxifen. METHODS: The estrogen receptor positive human breast carcinoma cell line MCF-7 was treated with (E/Z)-endoxifen hydrochloride in the presence and absence of a defined estradiol concentration. Each concentration of the drug was combined with fermented Viscum album L. extracts (VAE) at clinically relevant doses, and proliferation, apoptosis and cell cycle were analyzed. In parallel, possible inhibition of CYP3A4/5 and CYP2D6 was investigated using 50-donor mixed gender pooled human liver microsomes (HLMs). RESULTS: VAE did not inhibit endoxifen induced cytostasis and cytotoxicity. At higher concentrations, VAE showed an additive inhibitory effect. VAE preparations did not cause inhibition of CYP3A4/5 and CYP2D6 catalyzed tamoxifen metabolism. CONCLUSIONS: The in vitro results suggest that mistletoe preparations can be used in combination with tamoxifen without the risk of HDIs.

[Bilateral hypoplasia of the internal carotid arteries associated with aneurysm of the right posterior communicating artery. Apropos of a case]. / Hypoplasie bilatérale des carotides internes associée à un anévrysme de la communicante postérieure droite. A propos d'une observation.

The authors report a case of bilateral hypoplasia of the internal carotid arteries associated with aneurysm of the right posterior communicating artery in a 17 year old female patient. This anomaly was discovered following a meningeal haemorrhage, which recurred 18 months later, causing the patient's death. Surgical operation was refused by the patient and her family. Bilateral hypoplasia of the internal carotid arteries is a rare congenital malformation (16 cases have been reported in the literature, our case constitutes the 17th). It is distinguished from aplasia by the presence of a patent but very reduced vascular lumen, while aplasia is associated with vestiges of non-patent vessels. The mechanism of development of such a malformation is unclear: some authors have suggested secondary regression of the internal carotid artery following a phase of normal development, while others consider it to represent arrest of the development of the internal carotid artery, at a given moment in time. The frequency of associated aneurysm would be due to the haemodynamic disruption induced by the malformation, especially as parietal defects are more frequent in a malformed vasculature. Bilateral hypoplasia of the internal carotid arteries may be compatible with normal life for an indefinite period of time due to the development of a large number of collateral vessels. However, the new vasculature is threatened by rupture with meningeal haemorrhage and by acute ischaemia, which would probably involve another aetiological factor.