To the Editor.—
Togias et al,1 in their Jan 10 article, demonstrate that azatadine base inhibits mediator release from human mast cells but state that the mechanism of this inhibition is unknown.I would like to suggest that the mechanism in question is the prevention of calcium entry into the mast cell through voltage-dependent calcium channels. The similarity in structure of azatadine to cyproheptadine has been noted by Lichtenstein and Gillespie2 and by the Schering Corporation in its Basic Data Book. Donatsch et al3 concluded that cyproheptadine inhibited depolarization-dependent calcium entry into rat pancreatic B cells. Lowe et al4 concluded that cyproheptadine reduced the flow of calcium ion through the voltage-dependent calcium channels in guinea pig smooth muscle. Ishizaka and Ishizaka5 concluded that entry of calcium into rat mast cells triggers histamine release. Togias et al postulate that the interaction of azatadine with H1
Lehrer JF. Inhibition of Mediator Release in Azatadine. JAMA. 1986;255(24):3366–3367. doi:10.1001/jama.1986.03370240036028
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