Effects of ondansetron on respiratory pattern and sensation of experimentally induced dyspnea.
BACKGROUND
Dyspnea remains a therapeutic challenge, especially in chronic respiratory conditions. Recent studies have shown that the induction of unpleasant dyspnea sensations activates areas in the insular cortex.


OBJECTIVE
This study was designed to investigate the potential effects of ondansetron, a potent anti-serotonin agent, on induced dyspnea sensation.


METHODS
A randomized double blind study.


METHODS
Pulmonary Function Laboratory of Hospital das Clínicas de Ribeirão Preto.


METHODS
Ten healthy male volunteers (mean age +/- standard error = 23.1 +/- 0.41 years) without respiratory diseases and showing normal spirometric tests.


METHODS
Uncomfortable breathing was induced in the volunteers on two different days, via the use of inspiratory resistors (loads of 0, 7, 14 and 21 cm H2O/l/sec) and breathholding, two hours after taking 8 mg of ondansetron (Ond) or placebo (Plac).


METHODS
Respiratory discomfort during breathing under loading was evaluated on a 100-mm visual analog scale. The maximum length of time of voluntary apnea was measured in seconds.


RESULTS
The mean maximum voluntary apnea time did not differ between the ondansetron and placebo days (Plac = 96 +/- 6.6 sec vs. Ond = 100 +/- 7.9 sec). Ondansetron did not influence the dyspnea sensation induced by different inspiratory loads (0 cm H2O/l/sec: Ond = 1.4 mm +/- 0.44 vs. Plac = 2.1 +/- 0.85 mm; 7 cm H2O/l/sec: Ond = 16.6 +/- 2.74 mm vs. Plac = 13.7 +/- 2.06 mm; 14 cm H2O/l/sec; Ond = 30.5 +/- 4.50 mm vs. Plac = 27.1 +/- 3.44 mm; 21 cm H2O/l/sec: Ond = 50.3 +/- 6.72 mm vs. Plac = 49.4 +/- 6.72 mm). Ondansetron led to significant decreases in tidal volume under basal conditions and when breathing under the highest inspiratory loading (0 cm H2O/l/sec: Ond = 0.83 +/- 0.26 l vs. Plac = 1.0 +/- 0.28 l; 21 cm H2O/l/sec: Ond = 0.86 +/- 0.23 l vs. Plac = 1.1 +/- 0.22 l)


CONCLUSIONS
The present results suggest that 5-HT3 receptors do not play an important role in the mediation of dyspnea sensations.
Martinez
José Antônio Baddini
JA
Departamento de Medicina Interna, Faculdade de Medicina de Ribeirão Preto, São Paulo, Brazil. jabmarti@fmrp.usp.br
Rocha
Fábio Senra
FS
Sobrani
Elizabet
E
Galhardo
Fabíola Paula Lovreto
FP
Terra Filho
João
J
D000328:Adult; D004311:Double-Blind Method; D004417:Dyspnea / Q000188:drug therapy*; D006801:Humans; D008297:Male; D017294:Ondansetron / Q000627:therapeutic use*; D012702:Serotonin Antagonists / Q000627:therapeutic use*; D013147:Spirometry; D018709:Statistics, Nonparametric
D012702:Serotonin Antagonists; D017294:Ondansetron