[...] terfenadine and loratadine inhibit spontaneous growth of neoplastic mast cells

nanonug

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Exp Hematol. 2010 Oct;38(10):896-907. Epub 2010 Jun 1.
H1-receptor antagonists terfenadine and loratadine inhibit spontaneous growth of neoplastic mast cells.

Hadzijusufovic E, Peter B, Gleixner KV, Schuch K, Pickl WF, Thaiwong T, Yuzbasiyan-Gurkan V, Mirkina I, Willmann M, Valent P.
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Department for Companion Animals and Horses, Clinic for Internal Medicine and Infectious Diseases, University of Veterinary Medicine Vienna, Vienna, Austria.
Abstract

OBJECTIVE:

In mast cell (MC) neoplasms, clinical problems requiring therapy include local aggressive and sometimes devastating growth of MCs and mediator-related symptoms. A key mediator of MCs responsible for clinical symptoms is histamine. Therefore, use of histamine receptor (HR) antagonists is an established approach to block histamine effects in these patients.
MATERIALS AND METHODS:

We screened for additional beneficial effects of HR antagonists and asked whether any of these agents would also exert growth-inhibitory effects on primary neoplastic MCs, the human MC line HMC-1, and on two canine MC lines, C2 and NI-1.
RESULTS:

We found that the HR1 antagonists terfenadine and loratadine suppress spontaneous growth of HMC-1, C2, and NI-1 cells, as well as growth of primary neoplastic MCs in all donors tested (human patients, n = 5; canine patients, n = 8). The effects of both drugs were found to be dose-dependent (IC(50): terfenadine, 1-20 μM; loratadine, 10-50 μM). Both agents also produced apoptosis in neoplastic MCs and augmented apoptosis-inducing effects of two KIT-targeting drugs, PKC412 and dasatinib. The other HR1 antagonists (fexofenadine, diphenhydramine) and HR2 antagonists (famotidine, cimetidine, ranitidine) tested did not exert substantial growth-inhibitory effects on neoplastic MCs. None of the histamine receptor blockers were found to modulate cell-cycle progression in neoplastic MCs.
CONCLUSIONS:

The HR1 antagonists terfenadine and loratadine, in addition to their antimediator activity, exert in vitro growth-inhibitory effects on neoplastic MCs. Whether these drugs (terfenadine) alone, or in combination with KIT inhibitors, can also affect in vivo neoplastic MC growth remains to be determined.
Copyright © 2010 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.
PMID: 20570632
 

nanonug

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Caveat: this is for neoplastic mast cells in vitro. Whether the same applies to in vivo non-neoplastic mast cells is just not known. However, I am going to replace fexofenadine with loratadine just in case. As loratadine makes me sleepy, I am going to take it at night.
 

ukxmrv

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I take Loratadine (1) at night during the hayfever season. Also sedating for me (most hayfever drugs are even the so-called non-sedating ones)

Hope it helps you.
 
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