dextromethorphan and Lung-Diseases--Obstructive

We studied the effects of a non-narcotic, centrally acting antitussive, fominoben (PB89), on hypoxia in sixty patients suffering from chronic obstructive lung diseases (COLD), utilizing a double-blind method and using the antitussive dextromethorphan as a reference drug. By the oral administration of a dose of 2 fominoben tablets (160 mg) three times a day for 2 weeks, a significant increase in arterial O2 pressure (PaO2), a decrease in arterial CO2 pressure (PaCO2), and a rise in pH were observed. However, alveolar-arterial O2 difference (A-aDO2) was not improved. On the other hand, after administration of a dose of 2 dextromethorphan tablets (30 mg) three times a day for 2 weeks, no increase in PaO2, no decrease in PaCo2 and no improvement in A-aDO2 were observed, although a rise in pH was seen. The increase in PaO2 by fominoben was marked in COLD with dyspnoea. No improvement of A-aDO2 despite a decrease in PaCO2 suggests that fominoben might increase alveolar ventilation, in spite of its effect as an antitussive, exerting a favourable effect on hypoxia. It is, therefore, speculated that the cough centre and the respiratory centre are capable of functioning independently of each other.

Topics: Aged; Antitussive Agents; Dextromethorphan; Double-Blind Method; Female; Humans; Hypoxia; Levorphanol; Lung Diseases, Obstructive; Male; Middle Aged; Morpholines; Partial Pressure; Respiratory Center

We have previously shown that the exercise performance of patients with severe chronic obstructive pulmonary disease (COPD) can be increased with the administration of oral morphine (0.8 mg.kg-1). The purpose of this study was to determine whether the administration of dextromethorphan (DXT), an antitussive structurally similar to codeine, would result in increased exercise performance and decreased dyspnoea in patients with COPD, without the side-effects of opiates. Six eucapnic patients (mean age = 66 +/- 3.8 yrs) with COPD (mean forced expiratory volume in one second (FEV1) = 1.01 +/- 0.07 l) underwent two incremental cycle ergometer tests to exhaustion (Emax) and assessment of their hypercapnic and hypoxic ventilatory responses and mouth occlusion pressure responses following first the oral administration of placebo (P) and then dextromethorphan (60 mg) in a single-blind fashion. There was no statistically significant difference in the maximal exercise performance, perceived dyspnoea (modified Borg scale), breathing pattern or expired gases after the two different treatments. In addition, the ventilatory response to CO2 production during exercise (delta VE/VCO2) and the ventilatory and mouth occlusion pressure responses to hypoxia and hypercapnia did not differ significantly after DXT as compared with after P. Indeed the exercise performance was poorer and the ventilatory responses were brisker after DXT. We conclude from this study that the administration of this opiate analogue does not improve the exercise capacity or decrease the ventilatory response of patients with COPD.

Topics: Aged; Carbon Dioxide; Dextromethorphan; Dyspnea; Exercise Test; Humans; Lung Diseases, Obstructive; Middle Aged; Oxygen; Oxygen Consumption; Respiratory Mechanics; Single-Blind Method