The effect of almitrine on the steady-state ventilatory response to carbon dioxide at rest and during exercise in man.

Almitrine has potential as a tool for testing the physiological role of the peripheral chemoreceptor. The effects of almitrine on CO2 chemosensitivity were studied at rest and during light exercise using a constant inflow technique that avoids the hyperoxia of rebreathing methods. The steady-state ventilatory response to CO2 was measured in two groups of six normal men before and 150 min after 100 mg oral almitrine bismesylate or placebo. One group was studied at rest, the other while pedalling at 50 W. The resting group showed a significant increase in CO2 response slope after almitrine when compared with placebo but there was no significant change in the response intercept. During exercise the individual results were very variable and after almitrine no significant change was seen in either the response slope or intercept. Control ventilation was not affected by almitrine in either group. Even in the absence of marked hyperoxia the effect of almitrine on CO2 sensitivity at rest in small. The lack of effect at 50 W is against any important role for the peripheral chemoreceptor during light exercise but other interpretations are possible.