Almitrine bismesylate.

There is a place in therapy for an orally active respiratory stimulant. Almitrine bismesylate is a respiratory agonist which: 1. Effectively increases PaO2 in a unique way, principally by stimulation of the peripheral chemoreceptors. 2. Appears to have an effect on blood gases through mechanisms other than stimulation of ventilation which could be on ventilation-perfusion relationships, or even metabolic, for which there is as yet no firm evidence. 3. After chronic administration has a plasma elimination half-life of 20-30 days. This could result in plasma accumulation of the drug, and means that drug intolerance problems are not readily resolved by stopping the tablets. Special dosing schedules may be required. 4. Has an action on the pulmonary vasculature which is mainly vasoconstrictor (and vasodilator in acute hypoxia in animal studies). Present evidence regarding the effect of long-term administration on pulmonary haemodynamics is conflicting. 5. May have an adverse, possibly dose-related effect on dyspnoea in some patients - more work is needed on patient characteristics associated with good drug tolerance. 6. Has an adverse effect on peripheral nerve function in some patients. Whether this is de novo, or aggravation of a preexisting lesion has yet to be established. Thus, although almitrine is effective in increasing PaO2 and as an experimental drug is fascinating, its clinical use remains to be clearly defined. The most powerful argument for the therapeutic use of almitrine would be the demonstration of a beneficial effect on mortality; either in acute exacerbations of respiratory failure, or in the same way as LTO2 exerts an effect in chronically hypoxaemic patients.