Description:
<jats:p>Passive transfer (PK) tests were performed with a reaginic serum on a recipient reacting with an immediate and a more prolonged reaction when specifically challenged. Both reactions are thought to be mediated by IgE immunology. Ketotifen, a cycloheptathiophene derivative, and clemastine, given to the recipient in maximal clinical doses for 3 days, inhibited the immediate reaction. Ketotifen had a very slight effect also on the prolonged reaction.</jats:p><jats:p>The results indicate that the<jats:italic>in vivo</jats:italic>effects of ketotifen in the human system are due not so much to mast cell inhibitory mechanisms, but more to post‐release antihistaminic and some anti‐inflammatory properties.</jats:p>