Inhibitory effects of terfenadine on the rising phase of action potentials and sinus rates in isolated guinea-pig myocardium.
1. Effects of terfenadine on the ventricular action potential and sinus rate of isolated guinea-pig myocardial preparations were examined to elucidate whether the drug has any cardioinhibitory effect. 2. Terfenadine significantly and concentration dependently decreased the maximum rate of rise (Vmax) of action potentials, the decrease of which was 60% of the control value at 2 x 10(-5) M. 3. Terfenadine decreased the sinus rate concentration dependently at 10(-6) M and higher concentrations; in some preparations, spontaneous beating was abolished at 2 x 10(-5) M (sinus arrest). 4. On the other hand, KW-4679 ((Z)-11-[3-(dimethylamino)propylidene]-6-11-dihydrodibenz[b, e]oxepin- 2-acetic acid hydrochloride), a new antiallergic drug having higher antiallergic potency than terfenadine, exerted a weaker inhibitory effect on the Vmax without affecting the sinus rate. 5. In conclusion, the antiallergic drug terfenadine has inhibitory effects on isolated myocardia. The cardioinhibitory effects of antiallergic drugs seem to be independent of their antiallergic potency.
Tanaka
H
H
Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Masumiya
H
H
Kato
Y
Y
Shigenobu
K
K
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D018926:Anti-Allergic Agents / Q000494:pharmacology*; D003864:Depression, Chemical; D003990:Dibenzoxepins / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D000069605:Olopatadine Hydrochloride; D016593:Terfenadine / Q000494:pharmacology*
D018926:Anti-Allergic Agents; D003990:Dibenzoxepins; D000069605:Olopatadine Hydrochloride; D016593:Terfenadine