Am. J. Respir. Crit. Care Med., Vol 151, No. 3, 03 1995, 692-697.
Effects of dexfenfluramine on hypoxic pulmonary vasoconstriction and embolic pulmonary hypertension in dogs
R Naeije, P Wauthy, M Maggiorini, M Leeman and M Delcroix
Laboratory of Cardiovascular and Respiratory Physiology, Erasme University Hospital, Brussels, Belgium.
There has been suggestion of a possible relationship between the intake of
the appetite suppressant dexfenfluramine and the development of primary
pulmonary hypertension. We investigated the pulmonary vascular effects of
acute intravenous dexfenfluramine in pentobarbital- anesthetized dogs
ventilated in hyperoxia (fraction of inspired oxygen, FIO2, 0.4) and either
challenged with a FIO2 of 0.1 to induce hypoxic pulmonary hypertension (n =
20) or given autologous blood clots to induce embolic pulmonary
hypertension (n = 6). Pulmonary vascular tone was evaluated by multipoint
(mean pulmonary artery pressure [Ppa] - pulmonary artery occluded pressure
[Ppao])/cardiac output (Q) plots. Hypoxia increased Ppa - Ppao over the
entire range of Q studied, from 1.5 to 4.0 L/min/m2, in 12 dogs
(responders) and had no significant effect on (Ppa - Ppao)/Q plots in 8
other dogs (nonresponders). Dexfenfluramine did not affect (Ppa - Ppao)/Q
plots in 6 responders but shifted (Ppa - Ppao)/Q plots to higher pressures
in hypoxia in 6 nonresponders (p < 0.001). Dexfenfluramine had no effect
on (Ppa - Ppao)/Q plots in the 6 dogs with embolic pulmonary hypertension.
Because dexfenfluramine has serotoninergic properties, we compared the
effects of ketanserin, a serotonin (5-hydroxytryptamine, 5-HT) S2 receptor
antagonist, on naturally present versus dexfenfluramine- restored hypoxic
pulmonary vasoconstriction. Ketanserin did not affect hyperoxic or hypoxic
pulmonary vascular tone, neither in 6 responders nor in 2 nonresponders
with dexfenfluramine-restored hypoxic vasoconstriction. We conclude that
dexfenfluramine restores hypoxic pulmonary vasoconstriction in dogs with
weak or absent hypoxic pressor response and that this effect is unlikely to
be mediated by activation of 5-HT S2 receptors.
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Copyright © 1995 American Thoracic Society
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